Photovoltaic power generation and reversible solid oxide battery coupled energy system and multi-mode cooperative operation method

Abstract

The invention relates to the technical field of renewable energy source storage and conversion, and particularly provides a photovoltaic power generation and reversible solid oxide battery coupled energy system and a multi-mode cooperative operation method, and the core scheme of the invention is that seamless switching of a single RSOC electric pile between an SOEC mode and an SOFC mode is realized through a valve control system; redundant electric energy drives the RSOC to electrolyze water to generate green hydrogen for storage; and in the photovoltaic valley period, the stored hydrogen is used for power generation and energy supply. The system is integrated with a heat recovery unit, waste heat gradient utilization is achieved, and efficiency is improved. The method has the beneficial effects of reducing equipment cost, avoiding starting and stopping thermal cycle, prolonging the service life, realizing stable supply of electric energy peak load shifting, and being capable of being expanded to renewable energy scenes such as wind energy. Through an innovative coupling mechanism, the problems of storage and volatility of renewable energy sources are efficiently solved.

Description

Technical Field

[0001] This invention belongs to the field of renewable energy storage and conversion technology, specifically relating to a photovoltaic power generation and reversible solid oxide battery coupled energy system and a multi-mode collaborative operation method, which is used to solve the problems of large fluctuations in photovoltaic power generation and difficulty in storing electrical energy. Background Technology

[0002] Reversible solid oxide batteries (RSOCs) are a type of highly efficient electrochemical device that combines the functions of solid oxide electrolyzers (SOECs) and solid oxide fuel cells (SOFCs), enabling bidirectional conversion between electrical and chemical energy.

[0003] In the prior art, similar solutions include: Existing similar solution 1: such as Figure 2 As shown, combining complementary schemes of solar thermal steam generation, photovoltaic power generation, SOEC water electrolysis for hydrogen production, and SOFC power generation, the system mainly consists of a solar thermal steam generation unit, a photovoltaic power generation unit, a solid oxide electrolyzer (SOEC) hydrogen production unit, a solid oxide battery (SOFC) power generation unit, and a hydrogen storage unit.

[0004] Due to the strong periodicity and instability of solar radiation, which is concentrated in the midday hours and occurs at night when there is no sunlight, photovoltaic and solar thermal systems cannot operate. Therefore, during the day or when sunlight is abundant, the system primarily generates electricity from the photovoltaic system to supply power to users or feed it into the grid. While ensuring stable output, a portion of the electricity is extracted for SOEC water electrolysis to produce hydrogen. The high-temperature steam required for hydrogen production is provided by the solar thermal system. The hydrogen produced by water electrolysis is cooled and stored in a hydrogen storage tank. The remaining steam is cooled to form condensate, which is stored in a water storage tank. After being heated in a heat-collecting tower, it can be used to generate steam for further hydrogen production through water electrolysis. Furthermore, the pure oxygen produced during hydrogen production can be used as a byproduct for other purposes. During periods of insufficient sunlight and at night, the photovoltaic system cannot meet the requirements for stable output. The system mainly generates electricity through SOFC (Solar-Optical Fuel Cell) systems. In the power generation process, the fuel used at the anode is hydrogen stored in a hydrogen storage tank after water electrolysis by SOEC (Solar-Optical Electrolysis). After the reaction, water vapor is generated, cooled, and stored in a water storage pool for subsequent SOEC water electrolysis to produce hydrogen. The cathode is air. The exhaust gas after the reaction is discharged after heat recovery as needed, and the generated electricity is given to users or transmitted to the power grid.

[0005] Existing similar solution 2: such as Figure 3 As shown, a reversible solid oxide fuel cell-electrolyte system and its operation method are disclosed. The system adopts the RSOC stack module fuel exhaust gas recirculation process. By adjusting the opening and closing of shut-off valves at different positions on the pipeline, the system can freely switch between SOFC mode and SOEC mode.

[0006] In SOFC mode, before system startup, open the shut-off valves between the RSOC stack module fuel outlet and the burner, the shut-off valve between the burner and the fuel preheater, the shut-off valve between the heat exchange steam generator and the waste heat recovery unit, and the shut-off valve between the heat exchange steam generator and the reformer. Close the shut-off valves between the RSOC stack module fuel outlet and the fuel preheater, the shut-off valve from the heat exchange steam generator outlet to the product hydrogen, and the shut-off valve on the burner's inlet natural gas pipeline. The system supplies natural gas, air, and deionized water. The circulating fan speed gradually reaches the target value, and the system heats up and generates electricity at a certain rate. Power enhancement: When the system enters the rated power generation state in SOFC mode, the shut-off valve from the heat exchange steam generator to the reformer is closed. The system does not need to provide deionized water from the outside to generate fresh steam. The system only needs to be supplied with natural gas and air. A portion of the fuel exhaust gas from the RSOC stack module outlet and the high-temperature air from the RSOC stack module outlet enter the burner for mixing and combustion. The resulting high-temperature flue gas heats the fuel preheater and air preheater. Another portion of the fuel exhaust gas from the RSOC stack module outlet mixes with fresh natural gas under the action of the circulating fan and enters the reformer for catalytic reaction, and finally enters the RSOC stack module to participate in power generation.

[0007] In SOEC mode, before system startup, open the shut-off valves between the RSOC stack module fuel outlet and the fuel preheater, open the shut-off valve from the heat exchange steam generator outlet to the product hydrogen, open the shut-off valve from the heat exchange steam generator to the reformer, and open the shut-off valve on the burner inlet natural gas pipeline. Close the shut-off valves between the RSOC stack module fuel outlet and the burner, close the shut-off valve between the burner and the fuel preheater, close the shut-off valve from the heat exchange steam generator to the waste heat recovery, and shut down the circulating fan. The system supplies hydrogen, deionized water, air for startup, and natural gas for combustion. The system heats up and increases the hydrogen production load at a certain rate. When entering the rated electrolysis hydrogen production state in EC mode, the circulating fan is turned on to the target speed. The system does not require external hydrogen supply. The system only needs to be supplied with deionized water, air, and natural gas for the burner. A portion of the fuel exhaust gas from the RSOC stack module outlet is mixed with fresh water vapor under the action of the circulating fan and re-enters the RSOC stack module. Another portion of the fuel exhaust gas from the RSOC stack module outlet enters the fuel preheater and heat exchange steam generator successively to achieve cascade utilization of heat. Finally, liquid water is condensed and separated to obtain product hydrogen. External natural gas enters the burner and mixes with the high-temperature air from the RSOC stack module outlet for combustion. The high-temperature flue gas generated is used to heat fresh air.

[0008] In the existing similar scheme 1, two stack modules, SOFC and SOEC, are used for power generation and electrolysis respectively. They need to be started and stopped frequently. Due to the high operating temperature of the stack, thermal cycling will accelerate the damage of the stack, thereby affecting the service life of the stack. The energy cascade utilization is also not perfect. In addition, compared with using a single reversible RSOC stack module, the equipment investment cost is high.

[0009] The existing similar scheme 2 uses RSOC stack modules for power generation and electrolysis modes, but does not explain the power output in the power generation mode, the source of the power required in the electrolysis mode, or the waste heat recovery and utilization.

[0010] Therefore, this invention uses renewable photovoltaic power generation coupled with reversible solid oxide batteries (RSOC) to convert unused electrical energy into chemical energy in fuel, and then converts the chemical energy in fuel back into electrical energy according to user needs. This solves the problems of large fluctuations and difficulty in storing electricity generated by renewable photovoltaic power generation, while also avoiding the reliability risks caused by frequent start-ups and shutdowns of RSOC, thus achieving efficient and stable operation of the RSOC system. Summary of the Invention

[0011] To address the shortcomings of existing technologies, the present invention aims to provide a photovoltaic power generation and reversible solid oxide battery coupled energy system and a multi-mode collaborative operation method, which mainly solves the problems of large fluctuations and difficulty in storage of renewable energy power, while avoiding the reliability risks caused by frequent start-up and shutdown of RSOC.

[0012] To achieve the above objectives, the present invention provides the following technical solution: A photovoltaic power generation coupled with a reversible solid oxide battery energy system includes: Photovoltaic power generation unit, used to generate direct current using solar energy; A boost module is connected to the photovoltaic power generation unit to boost the DC power generated by the photovoltaic system to the required voltage. A storage battery, connected to the boost module, is used to store electrical energy; An inverter, connected to the boost module and the battery, is used to convert direct current to alternating current. A reversible solid oxide battery (RSOC) stack is capable of switching between solid oxide electrolyzer (SOEC) mode and solid oxide fuel cell (SOFC) mode. The RSOC stack includes a fuel electrode, an air electrode, and an electrolyte. Hydrogen storage tanks are used to store hydrogen gas. The valve control system includes multiple shut-off valves for controlling fluid passages to achieve mode switching of the RSOC stack; The gas processing unit includes a fuel preheater, an air preheater, a steam generator, and a heat exchanger, used for preheating fluids and recovering heat. And a control unit, used to control the operation mode of the valve control system and the RSOC stack according to the photovoltaic power generation situation. During peak photovoltaic power generation periods, the system operates in SOEC mode, using excess electricity to electrolyze water to produce hydrogen, which is then stored in the hydrogen storage tank. During off-peak photovoltaic power generation periods, the system operates in SOFC mode, using the hydrogen in the storage tank to generate electricity.

[0013] Preferably, the valve control system includes eight shut-off valves, from shut-off valve 1 to shut-off valve 8, and mode switching is achieved through combinations of valve opening and closing: When starting in SOEC mode, open shut-off valves 1, 3, 4 and 6, and close other valves. First, purge with nitrogen for purging and preheating. When running in SOEC mode, close shut-off valves 1 and 6, open shut-off valves 2 and 7, and input start-up hydrogen, deionized water, air, circulating water and electrical energy. When switching from SOEC mode to SOFC mode for startup, shut off the circulating pump, fan, shut-off valves 3 and 7, open shut-off valves 1 and 6, purge with nitrogen first, then close shut-off valves 1 and 4, and open shut-off valves 2, 5 and 8. When operating in SOFC mode, shut-off valves 2, 5, 6, and 8 are open, while other shut-off valves are closed, allowing hydrogen, air, and circulating water to be supplied.

[0014] Preferably, the gas processing unit further includes a circulation pump and a fan for partially recycling the hydrogen generated at the fuel electrode back to the gas mixer in SOEC mode, and partially recycling the anode tail gas back to the gas mixer in SOFC mode.

[0015] Preferably, the heat recovery is achieved through hot water heat exchanger 1 and hot water heat exchanger 2: In SOEC mode, the fuel exhaust gas is used sequentially to heat the fuel preheater, steam generator and hot water heat exchanger 2, and finally condensed and separated to obtain product hydrogen. In SOFC mode, the flue gas generated by combustion is used to heat the fuel preheater and air preheater, and then the heat is recovered via hot water heat exchanger 1.

[0016] Preferably, the RSOC stack is in a hot standby state during mode switching, and the switching is achieved by adjusting the valve to avoid frequent start-stop.

[0017] A method for operating a photovoltaic power generation and reversible solid oxide battery coupled energy system includes the following steps: Step 1: During peak photovoltaic power generation, control the valve system to make the reversible solid oxide battery RSOC stack operate in SOEC mode, use excess photovoltaic power to electrolyze water to produce hydrogen, and store the hydrogen in a hydrogen storage tank. Step 2: During the off-peak period of photovoltaic power generation, the control valve system switches the RSOC stack to SOFC mode, using the hydrogen in the hydrogen storage tank to generate electricity, which is then supplied to users or stored in batteries. Step 3: The fluid is utilized in stages through the heat recovery unit, including recovering fuel tail heat in SOEC mode and recovering flue gas waste heat in SOFC mode.

[0018] Preferably, the SOEC mode operation includes: First, purge with nitrogen and preheat the system. Once the system reaches the electrolysis operating temperature of 650-800℃, then input start-up hydrogen, deionized water, air, circulating water, and electricity. Hydrogen is produced by an electrolysis reaction at the fuel electrode. Part of the hydrogen is recycled, and the other part is stored as product hydrogen. The oxygen produced at the air electrode is carried away from the system.

[0019] Preferably, the SOFC mode operation includes: Hydrogen, air, and circulating water are input, and an electrochemical reaction occurs at the fuel electrode to generate electricity, with fuel utilization controlled at 40%–70%. The tail gas from the anode is used for combustion heating, and a portion is recycled back to the gas mixer to continue participating in the reaction.

[0020] Preferably, the method is applicable to renewable energy scenarios where wind or geothermal energy replaces photovoltaic power generation.

[0021] Preferably, the hydrogen is green hydrogen, produced from renewable energy sources, and the system achieves peak shaving and valley filling of electricity and a stable supply.

[0022] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention uses a single reversible RSOC fuel cell stack module. Compared with the traditional two-module operation mode of electrolysis and power generation, the equipment investment cost is low. During switching, the RSOC system is temporarily in a hot standby state. The electrolysis and power generation modes are switched by adjusting the shut-off valve. Therefore, frequent start-stop is not required, which can effectively avoid the damage to the fuel cell stack caused by the thermal cycle during the start-stop process, thereby extending the service life of the system.

[0023] 2. This invention uses reversible solid oxide battery technology to convert non-storable electrical energy into chemical energy in hydrogen. In SOEC electrolysis mode, excess green electricity generated by photovoltaics is coupled to electrolyze water to produce green hydrogen, which is then stored. When electricity is needed, SOFC power generation mode can be switched to generate electricity using hydrogen as fuel, which plays a role in peak shaving and valley filling, thereby making up for the insufficient power supply of photovoltaics at night and achieving a stable power supply. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the photovoltaic power generation and reversible solid oxide battery coupled energy system of the present invention; Figure 2 This is a schematic diagram of a similar existing scheme 1 in the background art; Figure 3 This is a schematic diagram of a similar existing scheme 2 in the background art; Figure 4 This is a schematic diagram illustrating the working principle of SOFC. Figure 5 This is a schematic diagram illustrating the working principle of SOEC. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0026] The following reference Figures 1-5 This application describes a photovoltaic power generation and reversible solid oxide battery coupled energy system and multi-mode collaborative operation method provided in an embodiment of the present application.

[0027] A photovoltaic power generation coupled with a reversible solid oxide battery energy system includes: Photovoltaic power generation unit, used to generate direct current using solar energy; A boost module is connected to the photovoltaic power generation unit to boost the DC power generated by the photovoltaic system to the required voltage. A storage battery, connected to the boost module, is used to store electrical energy; An inverter, connected to the boost module and the battery, is used to convert direct current to alternating current. The reversible solid oxide battery (RSOC) stack can switch between solid oxide electrolyzer (SOEC) mode and solid oxide fuel cell (SOFC) mode. The RSOC stack includes a fuel electrode, an air electrode, and an electrolyte. Hydrogen storage tanks are used to store hydrogen gas. The valve control system includes multiple shut-off valves for controlling fluid passages to enable mode switching of the RSOC stack; The gas processing unit includes a fuel preheater, an air preheater, a steam generator, and a heat exchanger, used for preheating fluids and recovering heat. And a control unit, used to control the valve control system and the operating mode of the RSOC stack according to the photovoltaic power generation situation. During peak photovoltaic power generation periods, the system operates in SOEC mode, using excess electricity to electrolyze water to produce hydrogen, which is then stored in a hydrogen storage tank. During off-peak photovoltaic power generation periods, the system operates in SOFC mode, using the hydrogen in the storage tank to generate electricity.

[0028] Furthermore, the valve control system includes eight stop valves, from stop valve 1 to stop valve 8, and the mode switching is achieved through the combination of valve opening and closing: When starting in SOEC mode, open shut-off valves 1, 3, 4 and 6, and close other valves. First, purge with nitrogen for purging and preheating. When running in SOEC mode, close shut-off valves 1 and 6, open shut-off valves 2 and 7, and input start-up hydrogen, deionized water, air, circulating water and electrical energy. When switching from SOEC mode to SOFC mode for startup, shut off the circulating pump, fan, shut-off valves 3 and 7, open shut-off valves 1 and 6, purge with nitrogen first, then close shut-off valves 1 and 4, and open shut-off valves 2, 5 and 8. When operating in SOFC mode, shut-off valves 2, 5, 6, and 8 are open, while other shut-off valves are closed, allowing hydrogen, air, and circulating water to be supplied.

[0029] Furthermore, the gas processing unit also includes a circulation pump and a fan for partially recycling the hydrogen produced at the fuel electrode back to the gas mixer in SOEC mode, and partially recycling the anode tail gas back to the gas mixer in SOFC mode.

[0030] Furthermore, heat recovery is achieved through hot water heat exchanger 1 and hot water heat exchanger 2: In SOEC mode, the fuel exhaust gas is used sequentially to heat the fuel preheater, steam generator and hot water heat exchanger 2, and finally condensed and separated to obtain product hydrogen. In SOFC mode, the flue gas generated by combustion is used to heat the fuel preheater and air preheater, and then the heat is recovered via hot water heat exchanger 1.

[0031] Furthermore, the RSOC stack is in a hot standby state during mode switching, and the switching is achieved by adjusting the valve to avoid frequent start-stop.

[0032] A method for operating a photovoltaic power generation and reversible solid oxide battery coupled energy system includes the following steps: Step 1: During peak photovoltaic power generation, control the valve system to make the reversible solid oxide battery RSOC stack operate in SOEC mode, use excess photovoltaic power to electrolyze water to produce hydrogen, and store the hydrogen in a hydrogen storage tank. Step 2: During the off-peak period of photovoltaic power generation, the control valve system switches the RSOC stack to SOFC mode, using hydrogen in the hydrogen storage tank to generate electricity, which is then supplied to users or stored in batteries. Step 3: The fluid is utilized in stages through the heat recovery unit, including recovering fuel tail heat in SOEC mode and recovering flue gas waste heat in SOFC mode.

[0033] In a further embodiment, SOEC mode operation includes: Before system startup, open shut-off valves 1, 3, 4, and 6, and close the other shut-off valves. First, introduce nitrogen for purging and preheating. Then, turn on electric heaters 1 and 2 and purge with air at a controlled heating rate (generally 2°C / min, depending on the system's temperature requirements) to preheat the system. Once the system reaches the electrolysis operating temperature, close shut-off valves 1 and 6, and open shut-off valves 2 and 7. During system operation, startup requires hydrogen, deionized water, air, circulating water, and electricity. The system input hydrogen gas is mainly used to reduce the electrode materials of the RSOC and to reduce the active component Ni of the electrolysis reaction. During the initial stage of system operation, the hydrogen gas is mixed with water vapor in a gas mixer and preheated in the fuel preheater to reach the RSOC system's electrolysis operating temperature (the SOEC electrolysis operating temperature is generally 650-800℃; if the preheating temperature is not reached, heater 1 can be started for supplemental heating). This preheated gas is then introduced into the RSOC system, where an electrochemical reaction occurs at the fuel electrode to produce hydrogen and oxygen ions (2H₂O + 4e⁻). - =2H2+2O 2- The hydrogen produced at the fuel electrode is partially recycled back to the gas mixer via a circulating pump for re-reaction, while the other portion is stored as product hydrogen. This product hydrogen is first used to heat the fuel preheater to recover heat, then to heat the steam generator to vaporize deionized water into steam. Finally, after fully recovering heat in the hot water heat exchanger 2, liquid water is condensed and separated to obtain product hydrogen, which is then stored in a hydrogen storage tank. Oxygen ions produced at the fuel electrode are transferred to the air electrode via the electrolyte, losing electrons to generate oxygen (2O₂). 2- -4e -=O2); After the system reaches its rated operating condition, shut-off valve 2 is closed. No external hydrogen supply is required. The hydrogen generated by electrolysis is circulated back by a circulating pump and mixed with water vapor to ensure the reaction, thus guaranteeing that the fuel electrode is in a reducing atmosphere during water electrolysis. Deionized water entering the system is pumped to a steam generator and heated to form steam. Under rated operating conditions, this steam mixes with the hydrogen generated by the fuel electrode electrolysis reaction in a gas mixer. Air entering the system is pressurized by a fan and pumped to a filter to remove impurities. After being heated by an air preheater, it is introduced into the RSOC system's air electrode, where oxygen ions lose electrons to generate oxygen (2O2). 2- -4e - =O2) is promptly removed from the air electrode to heat the externally input air in the air preheater. After sufficient heat recovery via hot water heat exchanger 1, it is discharged at a high altitude. The circulating water entering the system is returned to the user after sufficient waste heat recovery via hot water heat exchanger 2 and hot water heat exchanger 1. The electrical energy entering the system is generated by photovoltaics. After being boosted to the required voltage by a boost module, the DC power generated by the photovoltaics is stored in a battery. Excess electrical energy is input into the RSOC system to provide power for the electrolysis reaction.

[0034] In a further embodiment, SOFC mode operation includes: Switch the system from SOEC operation mode to SOFC operation mode. First, shut off the circulating pump, fan, and shut-off valves 3 and 7. Open shut-off valves 1 and 6, purge with nitrogen for 10 minutes, then close shut-off valves 1 and 4, and open shut-off valves 2, 5, and 8. In SOFC operation mode, shut-off valves 2, 5, 6, and 8 are open, while other shut-off valves are closed. The system requires the input of hydrogen, air, and circulating water. The input hydrogen is preheated in the fuel preheater by the flue gas generated from fuel exhaust combustion to reach the RSOC system's power generation operating temperature (SOFC power generation operating temperature is generally 600-750℃; if the preheating temperature is not reached, the proportion of exhaust gas combustion can be increased). The hydrogen is then introduced into the RSOC system where an electrochemical reaction occurs at the anode to produce water (H2 + O2). 2- -2e - =H2O), the fuel utilization rate is generally about 40% to 70%. Part of the exhaust gas after the fuel reaction is burned in the burner to produce flue gas for system heating, while another part is circulated back to the gas mixer by a circulating pump to continue participating in the reaction. This improves fuel utilization and preheats the fuel gas to a certain extent. The air entering the system is pressurized by a fan and delivered to a filter to remove impurities. After being heated by an air preheater, it is introduced into the cathode of the RSOC system to provide oxygen for the electrochemical reaction, where oxygen ions (O2 + 4e-) are generated. - =2O 2-The electrolyte is transferred to the anode to react with hydrogen to produce water. The resulting air exhaust enters the burner and mixes with the fuel exhaust for combustion. The high-temperature flue gas produced by combustion is used for heating in two separate circuits: one for fuel preheating and the other for air preheating. Both heated flue gas undergo heat recovery in a hot water heat exchanger 1 before being discharged at a high altitude. The circulating water entering the system returns to the user after heat recovery in the hot water heat exchanger 1. The current generated by electron transfer due to the anode and cathode reactions forms electrical energy. The DC power generated by the SOFC is boosted to the required voltage by a boost module. A portion of this electrical energy is converted into AC power by an inverter for user use, while excess electricity is stored in a battery. When the SOFC's electrical energy is insufficient, it is supplemented by the energy stored in the battery from photovoltaic power generation. If this still cannot meet the user's electricity needs, it can also be supplemented by mains power.

[0035] In a further embodiment, the method is applicable to renewable energy scenarios where wind or geothermal energy replaces photovoltaic power generation.

[0036] In a further embodiment, the hydrogen is green hydrogen, produced from renewable energy sources, and the system achieves peak shaving and valley filling of electricity and a stable supply.

[0037] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0038] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A hybrid power system coupling photovoltaic power generation with a reversible solid oxide cell, characterized in that: Comprising: a photovoltaic power generation unit for generating direct current by solar energy; a voltage boosting module connected to the photovoltaic power generation unit for boosting the direct current generated by photovoltaic to a required voltage; a storage battery connected to the voltage boosting module for storing electric energy; an inverter connected to the voltage boosting module and the storage battery for converting direct current to alternating current; a reversible solid oxide cell (RSOC) stack capable of switching between a solid oxide electrolysis cell (SOEC) mode and a solid oxide fuel cell (SOFC) mode, the RSOC stack comprising a fuel electrode, an air electrode, and an electrolyte; a hydrogen storage tank for storing hydrogen; a valve control system comprising a plurality of stop valves for controlling fluid passages to achieve mode switching of the RSOC stack; a gas processing unit comprising a fuel preheater, an air preheater, a steam generator, and a heat exchanger for preheating and heat recovery of fluids; and a control unit for controlling the valve control system and the operating mode of the RSOC stack according to photovoltaic power generation conditions, wherein during a photovoltaic power generation peak period, the system operates in the SOEC mode, and excess electric energy is used for water electrolysis to produce hydrogen, which is stored in the hydrogen storage tank, and during a photovoltaic power generation valley period, the system operates in the SOFC mode, and hydrogen in the hydrogen storage tank is used for power generation.

2. The photovoltaic power and reversible solid oxide cell coupled energy system of claim 1, wherein: The valve control system comprises eight stop valves, namely stop valve 1 to stop valve 8, and mode switching is achieved by opening and closing combinations of the valves: When the SOEC mode is started, stop valves 1, 3, 4, and 6 are opened, and other valves are closed, nitrogen is first passed through for replacement and preheating; When the SOEC mode is running, stop valves 1 and 6 are closed, stop valves 2 and 7 are opened, and start-up hydrogen, deionized water, air, circulating water, and electric energy are inputted; When switching from the SOEC mode to the SOFC mode is started, the circulating pump, the fan, stop valves 3 and 7 are closed, stop valves 1 and 6 are opened, nitrogen is first passed through for replacement, then stop valves 1 and 4 are closed, and stop valves 2, 5, and 8 are opened; When the SOFC mode is running, stop valves 2, 5, 6, and 8 are in an open state, and other stop valves are closed, hydrogen, air, and circulating water are inputted.

3. The photovoltaic power and reversible solid oxide cell coupled energy system of claim 1, wherein: The gas processing unit further comprises a circulating pump and a fan for circulating part of the hydrogen generated by the fuel electrode back to the gas mixer in the SOEC mode, and for circulating part of the anode tail gas back to the gas mixer in the SOFC mode.

4. The photovoltaic power and reversible solid oxide cell coupled energy system of claim 1, wherein: The heat recovery is achieved through hot water heat exchanger 1 and hot water heat exchanger 2: In the SOEC mode, the fuel tail gas is used to sequentially heat the fuel preheater, the steam generator, and the hot water heat exchanger 2, and finally condenses and separates to obtain product hydrogen; In the SOFC mode, the flue gas generated by combustion is used to heat the fuel preheater and the air preheater, and then recovers heat through the hot water heat exchanger 1.

5. The photovoltaic power and reversible solid oxide cell coupled energy system of claim 1, wherein: The RSOC stack is in a hot standby state during mode switching, and switching is achieved by adjusting the valves to avoid frequent start-stop.

6. A method for operating a photovoltaic power generation and reversible solid oxide cell coupled energy system, characterized by: Comprising the following steps: Step 1: During the peak period of photovoltaic power generation, the valve system is controlled to make the reversible solid oxide cell (RSOC) stack operate in the SOEC mode, to use the excess photovoltaic power to electrolyze water to produce hydrogen, and to store the hydrogen in a hydrogen storage tank; Step 2: During the valley period of photovoltaic power generation, the valve system is controlled to make the RSOC stack switch to the SOFC mode, to use the hydrogen in the hydrogen storage tank to generate power, and to supply the power to users or store the power in a battery; Step 3: The fluid is used in stages through a heat recovery unit, including recovering fuel tail heat in the SOEC mode and recovering flue gas waste heat in the SOFC mode.

7. The method of claim 6, wherein: The SOEC mode operation includes: First, nitrogen is used to displace and preheat the system, and after the system reaches the electrolysis operating temperature of 650-800℃, startup hydrogen, deionized water, air, circulating water and power are inputted; The fuel electrode generates hydrogen through electrolysis, part of which is recycled, and the other part is stored as product hydrogen; The oxygen generated by the air electrode is taken out of the system.

8. The method of claim 6, wherein: The SOFC mode operation includes: Hydrogen, air and circulating water are inputted, the fuel electrode generates power through electrochemical reaction, and the fuel utilization rate is controlled at 40%-70%; Part of the anode tail gas is used for combustion to provide heat, and part of it is recycled back to the gas mixer to continue to participate in the reaction.

9. The method of claim 6, wherein: The method is suitable for renewable energy scenarios in which wind energy or geothermal energy replaces photovoltaic power generation.

10. The system of claim 1 or the method of claim 6, wherein: The hydrogen is green hydrogen, which is produced by renewable energy, and the system realizes peak shaving and stable supply of power.

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