SOFC-SOEC multi-energy storage and supply system and method

Abstract

A SOFC-SOEC multi-energy storage and supply system and method, the system comprising a fuel cell power generation subsystem, an electrolytic cell energy storage subsystem and a solar energy charging subsystem, the fuel cell power generation subsystem comprising a SOFC cell and a gas turbine unit, respectively generating electricity through internal chemical reactions of the cell, and passing high-temperature gas obtained by burning working steam of the cell in a combustion chamber into the gas turbine unit to generate electricity through work of the gas turbine unit; the electrolytic cell energy storage subsystem comprising a SOFC electrolytic cell, waste material and residual heat carried after burning of working steam of the cell being used as electrolytic raw material of the electrolytic cell; the solar energy charging subsystem converting solar energy into electric energy to provide the electrolytic cell with electric energy required for electrolytic reaction; the electrolytic cell being connected to an oxygen tank, oxygen being supplied by the oxygen tank during electrolytic reaction, and carbon oxide compounds output by the electrolytic cell being liquefied into natural gas in a methane reactor. The present application can increase total power generation of the system and improve power generation and energy conversion efficiency.

Description

Technical Field

[0001] This invention belongs to the field of energy recovery and utilization technology of fuel cells, specifically relating to an SOFC-SOEC multi-energy combined storage and supply system and method. Background Technology

[0002] In daily power grid supply, the imbalance between power supply and demand often occurs due to seasonal differences in electricity load. In particular, the frequent occurrence of extreme weather in recent years, the uncontrollability of seasonal changes, and the fact that some areas with high annual electricity demand have had a large amount of renewable energy abandoned due to conditions and technical limitations have resulted in a situation where energy utilization is low and power generation, storage and supply cannot meet the demand.

[0003] High-temperature solid oxide fuel cells (SOFCs) do not require precious metals as catalysts due to their high operating temperature, resulting in relatively low cell costs, rapid electrode reactions, and a wide range of fuel applications, making them suitable for various power generation scenarios. Furthermore, the waste heat from the exhaust gas of SOFCs has a high energy level, accounting for 37%–43% of the total system energy; therefore, increasing waste heat recovery from fuel cells to improve power generation efficiency is necessary and important. Summary of the Invention

[0004] The purpose of this invention is to address the problems in the prior art by providing a SOFC-SOEC multi-energy combined storage and supply system and method. This system combines the advantages of high-temperature solid oxide fuel cells (SOFC) and solid oxide electrolytic cells (SOEC) to recover energy from SOFC and SOEC respectively, effectively increasing the total power generation of the system, improving power generation efficiency and energy conversion efficiency, while meeting the needs of high-efficiency power generation, waste heat recovery and renewable energy storage and supply.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A SOFC-SOEC multi-energy combined storage and supply system includes: The fuel cell power generation system includes an SOFC battery and a gas turbine unit. The SOFC battery generates electricity through internal chemical reactions, and the gas turbine unit generates electricity by passing the high-temperature gas obtained after the working steam of the SOFC battery is burned in the combustion chamber. An electrolytic cell energy storage subsystem includes an SOEC electrolytic cell, wherein the waste obtained after the combustion of the working steam of the SOFC battery and the residual heat carried by the waste are used as the electrolytic raw materials for the SOEC electrolytic cell. The solar charging subsystem is used to convert solar energy into electrical energy to provide the electrical energy required for the electrolysis reaction of the SOEC electrolyzer. The SOEC electrolyzer is connected to an oxygen tank, which supplies oxygen during the electrolysis reaction. The electrolysis of carbon dioxide and water occurs inside the SOEC electrolyzer. The carbon oxides output from the SOEC electrolyzer enter the methanation reactor and are liquefied to obtain natural gas. The output oxygen is returned to the oxygen tank.

[0006] As a preferred embodiment, the fuel cell power generation system is connected to a fuel supply subsystem, an air supply subsystem, and a water supply subsystem; the fuel supply subsystem includes a reformer, a first mixer, a fuel preheater, and a fuel compressor that are sequentially connected to the anode of the SOFC cell; the air supply subsystem includes an air preheater and an air compressor that are sequentially connected to the cathode of the SOFC cell; and the water supply subsystem includes a water supply pipeline connected to the first mixer and a second water pump installed on the water supply pipeline.

[0007] As a preferred embodiment, the gas turbine unit includes a first turbine connected to the combustion chamber, the first turbine performs work to drive a generator to generate electricity; the gas after the first turbine performs work is passed into an air preheater and a fuel preheater as a heat source.

[0008] As a preferred embodiment, a first heat exchanger is installed on the water supply pipeline connected to the first mixer. The fuel preheater is connected to the first ORC subsystem via the first heat exchanger. The first ORC subsystem is a loop formed by connecting the first evaporator, the first expander, the condenser, and the first working fluid pump. The first heat exchanger is connected to the first evaporator. The waste obtained after the working steam of the SOFC battery is burned includes CO2. The CO2 is preheated by the first evaporator via a CO2 heat exchanger. The preheated CO2 is then fed into the SOEC electrolytic cell.

[0009] As a preferred embodiment, the waste obtained after the working steam of the SOFC battery is burned is also used as a heat source and fed into a second heat exchanger. The second heat exchanger is connected to a water supply pipeline. The water vapor obtained from the heat exchange in the second heat exchanger is mixed with the CO2 preheated by the CO2 heat exchanger in a third mixer. After mixing, the mixture is fed into the fuel electrode of the SOEC electrolytic cell.

[0010] As a preferred embodiment, the methanation reactor is located in the second ORC subsystem, which is a loop formed by connecting the methanation reactor, the second working fluid pump, the second evaporator, and the second expander.

[0011] As a preferred embodiment, the CO2 heat exchanger is also connected to the second heat exchanger via a second mixer, the second mixer is connected to the water supply pipeline via a third heat exchanger, and the third heat exchanger is connected to the second evaporator.

[0012] As a preferred embodiment, the CO gas output from the methanation reactor is passed into a water separator to remove water, and then liquefied and output through a second turbine.

[0013] As a preferred embodiment, the solar charging subsystem converts solar energy into electrical energy through a parabolic solar collector.

[0014] A method for SOFC-SOEC multi-energy combined storage and supply includes the following steps: At room temperature and pressure, air is compressed by an air compressor to reach the pressure required for the cathode of the SOFC battery. The air is then preheated by the working fluid at the outlet of the first turbine to reach the designed inlet temperature of the SOFC battery before being fed into the cathode inlet of the SOFC battery. Water is pumped by a second water pump and preheated to the designed inlet temperature and pressure by the working fluid at the outlet of the first turbine to reach the designed inlet temperature of the SOFC battery. Fuel is supplied by the liquefied natural gas pipeline network. The liquefied natural gas is compressed by a fuel compressor to reach the inlet pressure of the SOFC battery. After being mixed with water, it is reformed to reform hydrocarbons into CO and H2 before being fed into the anode of the SOFC battery as fuel. The products of the SOFC battery are divided into two paths. One path generates electricity through the first turbine and then serves as the working fluid for the Brayton cycle, providing a heat source for preheating the input air and fuel. The waste heat is then recovered through the first ORC subsystem and finally heat-treated and mixed with water for use as fuel electrode feedstock in the SOEC electrolyzer. The other path is burned and then directly used as a heat source for preheating water and fuel electrode feedstock in the SOEC electrolyzer. The solar charging subsystem converts solar energy into electrical energy to provide the electrical energy required for the electrolysis reaction in the SOEC electrolyzer. When the voltage value is higher than the open-circuit voltage of the SOEC electrolyzer, the SOEC electrolyzer's energy storage is activated, compressing the CO2 at the SOFC cell outlet and the water at the inlet to reach the design pressure of the SOEC electrolyzer. After step heat exchange at the outlet working fluid temperature of the SOFC cell burner, the working fluid reaches the design temperature of the SOEC electrolyzer and is then introduced into the fuel electrode of the SOEC electrolyzer. The working fluid at the outlet of the SOEC electrolyzer's fuel electrode reacts in the methanation reactor to produce methane, which is then passed through a water separator to remove water, and then liquefied by the second turbine before being output. Waste heat is recovered through the second ORC subsystem, ensuring that the temperature and pressure of the methanation reactor meet emission standards.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects: To enhance waste heat recovery from high-temperature solid oxide fuel cells (SOFCs) and improve power generation efficiency, solid oxide electrolytic cells (SOECs) are utilized. SOECs can effectively store electricity generated from renewable energy sources during the electrolysis process, thus coordinating renewable energy with load-side energy demand and acting as a peak-shaving and valley-filling mechanism to meet load-side energy quality requirements. This invention, a SOFC-SOEC multi-energy combined storage and supply system, combines the advantages of both SOFCs and SOECs. It recovers energy from both SOFCs and SOECs. Waste and residual energy generated after power generation by the fuel cell power generation system are mixed with and treated with water to serve as electrolytic feedstock for the SOEC electrolytic cell fuel electrode. This effectively increases the system's total power generation, improves power generation efficiency and energy conversion efficiency, and simultaneously meets the needs of high-efficiency power generation, waste heat recovery, and renewable energy storage and supply.

[0016] Furthermore, this invention utilizes two organic Rankine cycle subsystems to recover SOFC and SOEC energy respectively, and combines them with a multi-stage heat exchanger to achieve the tiered utilization of waste heat, so that the final SOFC product temperature and pressure meet emission standards. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 Principle block diagram of the SOFC-SOEC multi-energy combined storage and supply system according to an embodiment of the present invention; Figure 2 A schematic diagram of the implementation structure of the SOFC-SOEC multi-energy combined storage and supply system according to an embodiment of the present invention; In the attached diagram: 101-Fuel supply subsystem; 102-Air supply subsystem; 103-Water supply subsystem; 201-Fuel cell power generation system; 202-Electrolyte storage subsystem; 203-Solar charging subsystem; 301-First ORC subsystem; 302-Second ORC subsystem; 1-Air compressor; 2-Fuel compressor; 3-Air preheater; 4-Fuel preheater; 5-First mixer; 6-Reformer; 7- SOFC battery; 8- Combustion chamber; 9- First turbine; 10- First heat exchanger; 11- First evaporator; 12- First expander; 13- Condenser; 14- First working fluid pump; 15- CO2 heat exchanger; 16- Second heat exchanger; 17- Second mixer; 18- Third heat exchanger; 19- Third mixer; 20- First water pump; 21- SOEC electrolytic cell; 22- Oxygen tank; 23- Parabolic solar collector; 24- Methanation reactor; 25- Second working fluid pump; 26- Second evaporator; 27- Second expander; 28- Water separator; 29- Second turbine; 30- Second water pump. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, those skilled in the art can obtain other embodiments without creative effort.

[0020] See Figure 1 The SOFC-SOEC multi-energy combined storage and supply system of this invention includes a fuel supply subsystem 101, an air supply subsystem 102, a water supply subsystem 103, a fuel cell power generation system 201, a first ORC subsystem 301, a second ORC subsystem 302, an electrolyzer energy storage subsystem 202, and a solar charging subsystem 203.

[0021] The fuel cell power generation system 201 is a component that provides electrical energy to the system. The embodiment adopts an SOFC-GT hybrid power generation system, which includes SOFC (solid carbon fuel cell stack) and GT (gas turbine). This subsystem generates electricity through the chemical reaction inside the fuel cell and the working steam of the fuel cell is introduced into the combustion chamber for combustion to obtain high-temperature gas at the outlet, which then enters the turbine to do work and drive the generator to generate electricity. The SOFC serves as the pre-stage burner of the GT, and this subsystem improves the working capacity of the steam.

[0022] The electrolytic cell energy storage subsystem 202 includes an SOEC (solid oxide electrolyzer), a methanation reactor 24, a water separator 28, and a second turbine 29. Waste and residual heat from the fuel cell power generation system 201 are mixed with water and pre-treated before being used as electrolytic feedstock for the SOEC fuel electrode. During the day, the solar charging subsystem 203 converts solar energy into electricity using photovoltaic cells. When the SOEC is activated for energy storage, an external oxygen tank 22 supplies oxygen to the SOEC oxidation electrode, causing the electrolysis of carbon dioxide and water within the SOEC. The resulting carbon oxide products enter the methanation reactor 24 for further reaction, and the generated oxygen is treated and returned to the oxygen tank 22 for reuse.

[0023] The fuel supply subsystem 101 is used for supplying gas and reforming and preheating natural gas fuel before it enters the SOFC (solid carbon fuel cell stack), and includes a fuel supply pipeline, a fuel compressor 2, a first mixer 5, and a reformer 6.

[0024] The air supply subsystem 102 provides air to the SOFC (solid carbon fuel cell stack) and brings it to a certain pressure and temperature condition, and provides oxidant to the SOFC cathode, including an air compressor 1 and an air heat exchanger.

[0025] The water supply subsystem 103 mainly supplies water to the SOEC electrolyzer and heats it in multiple heat exchangers using waste heat from the burners, including water pumps and throttling valves.

[0026] The first ORC subsystem 301 includes a first evaporator 11, a first working fluid pump 14, a condenser 13, and a first expander 12.

[0027] The second ORC subsystem 302 includes a methanation reactor 24, a second working fluid pump 25, a second evaporator 26, and a second expander 27. This subsystem utilizes the fact that the methanation reaction is an exothermic reaction with a large temperature drop that allows the working fluid to undergo a phase change, and uses it as the evaporator of the original system. This feature makes better use of the characteristics of the chemical reaction, can save system material costs, and can improve energy conversion efficiency.

[0028] The solar charging subsystem 203 includes a parabolic solar collector trough 23, photovoltaic cells, and corresponding circuitry. The circuitry is equipped with a voltage sensor and a control switch. When the entire system is running, if the photovoltaic cell voltage is greater than the open-circuit voltage, the circuit switch automatically opens, allowing the photovoltaic cells to provide electrolytic energy to the SOEC (Solar Energy Storage Cell), and the system begins its energy storage function. When the voltage falls below the open-circuit voltage, the circuit disconnects, and the electrolysis process stops. This subsystem utilizes solar energy as its energy source, reducing system energy costs and exhibiting environmentally friendly and energy-saving characteristics.

[0029] See Figure 2In a specific system structure, the fuel cell power generation system 201 is connected to the fuel supply subsystem 101, the air supply subsystem 102, and the water supply subsystem 103. The fuel supply subsystem 101 includes a reformer 6, a first mixer 5, a fuel preheater 4, and a fuel compressor 2, which are sequentially connected to the anode of the SOFC cell 7. The air supply subsystem 102 includes an air preheater 3 and an air compressor 1, which are sequentially connected to the cathode of the SOFC cell 7. The water supply subsystem 103 includes a water supply pipeline connected to the first mixer 5 and a second water pump 30 installed on the water supply pipeline. The gas turbine unit includes a first turbine 9 connected to the combustion chamber 8. The first turbine 9 performs work to drive a generator to generate electricity. The gas after the first turbine 9 performs work is passed into the air preheater 3 and the fuel preheater 4 as a heat source. A first heat exchanger 10 is installed on the water supply pipeline connected to the first mixer 5. The fuel preheater 4 is connected to the first ORC subsystem 301 via the first heat exchanger 10. The first ORC subsystem 301 is connected to the first evaporator 11, the first expander 12, the condenser 13, and the first working fluid pump 14 to form a loop, and the first heat exchanger 10 is connected to the first evaporator 11. The waste obtained after the working steam of the SOFC battery 7 is burned includes CO2. The CO2 is preheated by the first evaporator 11 via the CO2 heat exchanger 15, and the preheated CO2 is fed into the SOEC electrolytic cell 21. The waste obtained after the working steam of the SOFC battery 7 is also fed into the second heat exchanger 16 as a heat source. The second heat exchanger 16 is connected to the water supply pipeline. The water vapor obtained by the heat exchange in the second heat exchanger 16 is mixed with the CO2 preheated by the CO2 heat exchanger 15 in the third mixer 19, and the mixture is then fed into the fuel electrode of the SOEC electrolytic cell 21. CO2 heat exchanger 15 and the second heat exchanger 16 are also connected via a second mixer 17. The second mixer 17 is connected to the water supply pipeline via a third heat exchanger 18, and the third heat exchanger 18 is connected to the second evaporator 26. The methanation reactor 24 is located in the second ORC subsystem 302, which is a loop formed by connecting the methanation reactor 24, the second working fluid pump 25, the second evaporator 26, and the second expander 27. The CO gas output from the methanation reactor 24 is passed into a water separator 28 to remove water, and then liquefied and output through a second turbine 29.

[0030] This invention also proposes a method for SOFC-SOEC multi-energy combined storage and supply, comprising the following steps: Air at normal temperature and pressure is compressed by air compressor 1 to reach the pressure required for the cathode of SOFC battery 7. The air is preheated by the working fluid at the outlet of the first turbine 9 to reach the designed inlet temperature value of SOFC battery 7, and then input into the cathode inlet of SOFC battery 7. Water is preheated to the designed inlet temperature and pressure of SOFC battery 7 by the second water pump 30 and the working fluid at the outlet of the first turbine 9. Fuel is supplied by liquefied natural gas pipeline. The liquefied natural gas is compressed by fuel compressor 2 to reach the inlet pressure value of SOFC battery 7. After being mixed with water, it is reformed to reform hydrocarbons into CO and H2, which are then introduced into the anode of SOFC battery 7 as fuel.

[0031] The products of SOFC battery 7 are divided into two streams. One stream generates electricity using the first turbine 9, which then serves as the working fluid in the Brayton cycle, providing a heat source for preheating the input air and fuel. Waste heat is then recovered through the first ORC subsystem 301, and finally, after heat treatment and mixing with water, it is used as fuel for the SOEC electrolyzer 21 fuel electrode. The other stream, after combustion, directly serves as a heat source for preheating water and the SOEC electrolyzer 21 fuel electrode, and is finally discharged after passing through a heat exchanger and throttling valve to meet emission standards. The entire waste gas waste heat process involves stepped heat exchange, fully utilizing the waste heat at each stage and reducing the final waste products to standard pressure and temperature before emission, thus improving energy conservation and environmental protection.

[0032] The solar charging subsystem 203 converts solar energy into electrical energy, providing the necessary power for the electrolysis reaction in the SOEC electrolyzer 21. When the voltage exceeds the open-circuit voltage of the SOEC electrolyzer 21, the SOEC electrolyzer 21 is activated to store energy, compressing the CO2 at the outlet of the SOFC battery 7 and the water at the inlet to the design pressure of the SOEC electrolyzer 21. After three-step heat exchange at the outlet working fluid temperature of the SOFC battery 7 burner, the working fluid reaches the design temperature of the SOEC electrolyzer 21 and is then introduced into the fuel electrode of the SOEC electrolyzer 21. The working fluid at the outlet of the fuel electrode of the SOEC electrolyzer 21 reacts in the methanation reactor 24 to produce methane, water, carbon monoxide, etc., mainly methane. The methane is then passed through a water separator 28 to remove water, and then liquefied by the second turbine 29 before being output. It can also be supplied to the natural gas pipeline network for use. The SOEC oxygen electrode product is stored in an oxygen tank 22 for sale or use. Waste heat is recovered through the second ORC subsystem 302, ensuring that the temperature and pressure of the methanation reactor 24 meet emission standards.

[0033] The above description is merely a preferred embodiment of the present invention and is not intended to limit the technical solution of the present invention in any way. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can be modified and replaced in several simple ways, and these modifications and replacements are all within the scope of protection covered by the claims.

Claims

1. A SOFC-SOEC multi-energy combined storage and supply system, characterized in that, include: The fuel cell power generation system (201) includes an SOFC battery (7) and a gas turbine unit. The SOFC battery (7) generates electricity through internal chemical reactions, and the high-temperature gas obtained by burning the working steam of the SOFC battery (7) in the combustion chamber (8) is introduced into the gas turbine unit to generate electricity by doing work through the gas turbine unit. The electrolytic cell energy storage subsystem (202) includes an SOEC electrolytic cell (21), wherein the waste obtained after the working steam of the SOFC battery (7) is burned and the residual heat carried by it are used as the electrolytic raw materials for the SOEC electrolytic cell (21); The solar charging subsystem (203) is used to convert solar energy into electrical energy to provide the electrical energy required for the electrolysis reaction of the SOEC electrolyzer (21). The SOEC electrolyzer (21) is connected to the oxygen tank (22). During the electrolysis reaction, the oxygen tank (22) supplies oxygen. The electrolysis of carbon dioxide and water occurs inside the SOEC electrolyzer (21). The carbon oxides output from the SOEC electrolyzer (21) enter the methanation reactor (24) and are liquefied to obtain natural gas. The output oxygen re-enters the oxygen tank (22). The fuel cell power generation system (201) is connected to the fuel supply subsystem (101), the air supply subsystem (102), and the water supply subsystem (103). The fuel supply subsystem (101) includes a reformer (6), a first mixer (5), a fuel preheater (4), and a fuel compressor (2) that are connected in sequence to the anode of the SOFC battery (7). The air supply subsystem (102) includes an air preheater (3) and an air compressor (1) that are connected in sequence to the cathode of the SOFC battery (7). The water supply subsystem (103) includes a water supply pipeline connected to the first mixer (5) and a second water pump (30) installed on the water supply pipeline. A first heat exchanger (10) is installed on the water supply pipeline connected to the first mixer (5). The fuel preheater (4) is connected to the first ORC subsystem (301) through the first heat exchanger (10). The first ORC subsystem (301) is connected to the first evaporator (11), the first expander (12), the condenser (13) and the first working fluid pump (14) to form a loop. The first heat exchanger (10) is connected to the first evaporator (11). The waste obtained after the working steam of the SOFC battery (7) is burned includes CO2. The first evaporator (11) preheats the CO2 through the CO2 heat exchanger (15). The preheated CO2 is then introduced into the SOEC electrolytic cell (21). The waste obtained after the working steam of the SOFC battery (7) is burned is also used as a heat source and fed into the second heat exchanger (16). The second heat exchanger (16) is connected to the water supply pipeline. The water vapor obtained by the second heat exchanger (16) and the CO2 preheated by the CO2 heat exchanger (15) are mixed in the third mixer (19) and then fed into the fuel electrode of the SOEC electrolytic cell (21). The gas turbine unit includes a first turbine (9) connected to the combustion chamber (8). The first turbine (9) performs work to drive a generator to generate electricity. The gas after the first turbine (9) performs work is fed into the air preheater (3) and the fuel preheater (4) as a heat source. The methanation reactor (24) is located in the second ORC subsystem (302), which is a loop formed by connecting the methanation reactor (24), the second working fluid pump (25), the second evaporator (26) and the second expander (27).

2. The SOFC-SOEC multi-energy combined storage and supply system according to claim 1, characterized in that, The CO2 heat exchanger (15) and the second heat exchanger (16) are also connected through the second mixer (17), the second mixer (17) is connected to the water supply pipeline through the third heat exchanger (18), and the third heat exchanger (18) is connected to the second evaporator (26).

3. The SOFC-SOEC multi-energy combined storage and supply system according to claim 1, characterized in that, The CO gas output from the methanation reactor (24) is fed into a water separator (28) to remove water, and then liquefied and output by a second turbine (29).

4. The SOFC-SOEC multi-energy combined storage and supply system according to claim 1, characterized in that, The solar charging subsystem (203) converts solar energy into electrical energy through a parabolic solar collector (23).

5. A method for SOFC-SOEC multi-energy combined storage and supply, characterized in that, The SOFC-SOEC multi-energy combined storage and supply system according to any one of claims 1 to 4 includes the following steps: Normal temperature and pressure air is compressed by air compressor (1) to reach the pressure required for the cathode of SOFC battery (7). The air is preheated by the working fluid at the outlet of the first turbine (9) to reach the designed inlet temperature value of SOFC battery (7) and then input into the cathode inlet of SOFC battery (7). Water is preheated by the second water pump (30) and the working fluid at the outlet of the first turbine (9) to reach the designed inlet value of SOFC battery (7). Fuel is provided by liquefied natural gas pipeline. The liquefied natural gas is compressed by fuel compressor (2) to reach the inlet pressure value of SOFC battery (7). After being mixed with water, it is reformed to reform hydrocarbons into CO and H2 and then introduced into the anode of SOFC battery (7) as fuel. The products of the SOFC battery (7) are divided into two paths. One path generates electricity through the first turbine (9) and serves as the working fluid for the Brayton cycle, providing a heat source for preheating the input air and fuel. The waste heat is then recovered through the first ORC subsystem (301), and finally, after heat treatment and mixing with water, it is used as the fuel electrode feedstock for the SOEC electrolyzer (21). The other path is directly used as a heat source for preheating water and the fuel electrode feedstock of the SOEC electrolyzer (21) after combustion. The solar charging subsystem (203) converts solar energy into electrical energy to provide the electrical energy required for the electrolysis reaction of the SOEC electrolyzer (21). When the voltage value is higher than the open circuit voltage of the SOEC electrolyzer (21), the SOEC electrolyzer (21) is activated to store energy, so that the CO2 at the outlet of the SOFC battery (7) and the water at the inlet are compressed to the design pressure of the SOEC electrolyzer (21). After step heat exchange at the outlet working fluid temperature of the SOFC battery (7) burner, the working fluid reaches the design temperature of the SOEC electrolyzer (21) and is introduced into the fuel electrode of the SOEC electrolyzer (21). The working fluid at the outlet of the fuel electrode of the SOEC electrolyzer (21) reacts in the methanation reactor (24) to generate methane, which is then introduced into the water separator (28) to remove water, and then liquefied by the second turbine (29) before being output. Waste heat is recovered through the second ORC subsystem (302) so that the temperature and pressure of the methanation reactor (24) reach the emission standards.

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