Solar fuel preparation system and method with electric-thermal chemical cycle coupling

Abstract

A highly efficient solar fuel preparation system and method coupled with an electric-thermal chemical cycle, the system mainly includes: a focusing frequency division subsystem, a three-step methane steam reforming subsystem, and a high-temperature water electrolysis hydrogen production subsystem; wherein the first solar spectrum obtained by the focusing frequency division subsystem drives the three-step methane steam reforming subsystem to perform a three-step methane water reforming reaction through heat collection; and the second spectrum obtained drives the high-temperature water electrolysis hydrogen production subsystem to perform a water electrolysis H2 reaction through a photovoltaic cell; the three-step methane steam reforming subsystem can provide the required heat energy, high-temperature water steam gas source and reducing atmosphere for the high-temperature water electrolysis hydrogen production subsystem, and the pure O2 produced by the high-temperature water electrolysis hydrogen production subsystem can be directly used in the three-step methane steam reforming subsystem. The present invention realizes the synergistic coupling of solar thermochemical and electrochemical processes, can efficiently produce pure hydrogen and high-quality synthesis gas, and efficiently converts solar energy into hydrocarbons and hydrogen fuels.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel preparation, and in particular to a solar fuel preparation system and method coupled with electric-thermal chemical cycles. Background Art

[0002] my country is a country rich in coal, poor in oil and little in gas, and burning coal will cause serious pollution to the environment. Energy issues are related to the national economy and people's livelihood, and are the main constraint on the rapid and healthy development of my country's economy. The development and utilization of renewable clean energy, especially the rational and effective use of solar energy, is an important means to solve this problem.

[0003] Solar energy is widely distributed, but it is discontinuous and unstable, so it is particularly important to find a way to store solar energy efficiently. At present, using solar energy to produce fuel is an effective way to collect, fix and store solar energy, but using solar energy to directly decompose water and carbon dioxide to produce fuels such as hydrogen and carbon monoxide has problems such as high reaction temperature and low efficiency.

[0004] Combining fossil fuels such as methane with solar chemistry to produce hydrogen and carbon dioxide by decomposing water and carbon dioxide can effectively reduce the reaction temperature and improve the efficiency of solar fuel production. Among them, the two-step methane chemical chain reforming has the advantages of not easy to deposit carbon and can produce high-quality synthesis gas with a H2 / CO molar ratio of 2 suitable for Fischer-Tropsch synthesis. However, the amount of hydrogen produced by the decomposition of water in the two-step methane chemical chain reforming oxidation process is small, and the amount of fuel produced by the high-cost oxygen carrier per unit mass is low. Summary of the invention

[0005] In view of this, the main purpose of the present invention is to provide a solar fuel preparation system and method coupled with an electric-thermal chemical cycle, in order to at least partially solve at least one of the above-mentioned technical problems.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] As one aspect of the present invention, a solar fuel preparation system coupled with an electric-thermal chemical cycle is provided, comprising: a light-collecting and frequency-dividing subsystem for collecting and frequency-dividing the solar spectrum to form a first light beam and a second light beam; a three-step methane steam reforming subsystem, comprising: a heat-collecting unit for converting the first light beam into thermal energy; and a reforming reaction unit, comprising: a reduction reactor, thermally connected to the heat-collecting unit, serving as an oxygen carrier MO z Reacts with methane to generate hydrocarbon fuel and oxygen carrier MO x Container; oxidation reactor, as water vapor and oxygen carrier MO x Reaction to generate MO y and hydrogen containers, as well as reoxidation reactors, as oxygen carriers MO yReacts with oxygen to form oxygen carrier MO z a container, wherein the reduction reactor is connected to the oxidation reactor to deliver MO to the oxidation reactor x , the oxidation reactor is connected to the reoxidation reactor to deliver MO to the reoxidation reactor y , the reoxidation reactor is connected to the reduction reactor to deliver MO to the reduction reactor z ; A high-temperature water electrolysis hydrogen production subsystem, comprising: a photovoltaic power generation unit, which converts the second light beam into electrical energy; and a solid oxide electrolysis cell, which is electrically connected to the photovoltaic power generation unit and thermally connected to the oxidation reactor, and serves as a container for generating hydrogen fuel by electrolyzing water vapor under the action of heat transferred from the oxidation reactor; the solid oxide electrolysis cell is also connected to the reoxidation reactor and the oxidation reactor, respectively, to transport oxygen to the reoxidation reactor and to pass a mixed gas of hydrogen output from the oxidation reactor and unreacted water vapor into the solid oxide electrolysis cell; and a heat exchange subsystem, which is connected to the reforming reaction unit and the solid oxide electrolysis cell through pipelines, respectively, to recover the heat of the hydrocarbon fuel, hydrogen and unreacted water vapor output from the reforming reaction unit, and the hydrogen and incompletely electrolyzed water vapor output from the solid oxide electrolysis cell.

[0008] As another aspect of the present invention, there is provided a method for preparing fuel using the solar fuel preparation system as described above, comprising:

[0009] Step 1: Concentrate and divide the solar spectrum to form a first light beam and a second light beam, wherein the first light beam is converted into thermal energy and the second light beam is converted into electrical energy;

[0010] Step 2: Using the heat energy to carry out a three-step methane steam reforming reaction with methane, water vapor and oxygen carrier as raw materials to obtain hydrocarbon fuel and hydrogen, and recovering the heat of the hydrocarbon fuel, hydrogen and unreacted water vapor, wherein the three-step methane steam reforming reaction includes: oxygen carrier MO z Reacts with methane to generate hydrocarbon fuel and oxygen carrier MO x , water vapor and the oxygen carrier MO x Reaction to generate MO y and hydrogen, and the oxygen carrier MO y Reacts with oxygen to form oxygen carrier MO z ;

[0011] Step 3: Passing a mixture of hydrogen and unreacted water vapor into a solid oxide electrolysis cell, using the electrical energy as well as water vapor and oxygen carrier MO x The waste heat of the reaction is used for electrolysis to produce hydrogen to obtain hydrogen fuel and oxygen, and the heat of the hydrogen output by the solid oxide electrolysis cell and the incompletely electrolyzed water vapor is recovered;

[0012] Step 4: Use the oxygen obtained in step 3 as a raw material and the oxygen carrier MO in step 2 y Reaction to generate oxygen carrier MO z .

[0013] Based on the above technical solution, the present invention has the following beneficial effects:

[0014] 1. The solar spectrum is divided into a first light beam and a second light beam, the first light beam is converted into heat energy for the three-step methane steam reforming subsystem to carry out a thermochemical cycle reaction, and the second light beam is converted into electrical energy for the high-temperature water electrolysis hydrogen production subsystem to carry out an electrolytic hydrogen production reaction. The oxidation reaction of the three-step methane steam reforming can provide the required heat energy and high-temperature water vapor for the electrolysis of the solid oxide electrolysis cell (SOEC), so that the waste heat of the thermochemical reaction is fully utilized, the extra energy consumption in the electrolytic hydrogen production process is avoided, and the amount of decomposed water is increased. The pure O2 electrolysis product of the SOEC can be directly used in the reoxidation reaction process of the three-step methane steam reforming, so that the oxygen carrier is fully oxidized and can react with as much methane as possible, so as to fully utilize the high-cost oxygen carrier, thereby realizing the synergistic coupling of thermochemistry and electrochemistry and improving the utilization efficiency of the solar spectrum.

[0015] 2. By dividing the solar spectrum, the power generation efficiency of photovoltaic cells is improved and the loss of light-to-electricity conversion is reduced, so that solar energy can be efficiently converted into hydrogen through water electrolysis.

[0016] 3. The hydrogen released by the three-step methane steam reforming is introduced into the cathode of the electrolytic cell together with the unreacted water vapor, providing a reducing atmosphere for the cathode to protect it, thereby improving the efficiency and effect of solar water electrolysis to produce H2.

[0017] 4. CH4 can be converted into hydrocarbon fuels, namely H2 and CO, and the molar ratio of H2:CO is 2, which meets the Fischer-Tropsch synthesis ratio and avoids the separation energy consumption and water-gas conversion energy consumption in the downstream chemical utilization process. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of a solar fuel preparation system with electric-thermal-chemical cycle coupling according to an embodiment of the present invention.

[0019] In the above drawings, the specific meanings of the reference numerals are as follows:

[0020] 1-solar energy concentration and frequency division device; 2-first heat exchanger;

[0021] 3-reduction reactor; 4-oxidation reactor;

[0022] 5-reoxidation reactor; 6-solid oxide electrolysis cell;

[0023] 7-second heat exchanger; 8-third heat exchanger;

[0024] 9- fourth heat exchanger; 10- photovoltaic cell;

[0025] 11- Shunt. DETAILED DESCRIPTION

[0026] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0027] In order to improve the efficiency of solar fuel production, increase the amount of hydrogen produced by decomposing water, and increase the amount of fuel prepared per unit mass of oxygen carriers, the present invention proposes an efficient solar fuel preparation system and method coupled with an electric-thermal chemical cycle.

[0028] Figure 1 Schematic diagram of a solar fuel preparation system coupled with an electric-thermal chemical cycle according to an embodiment of the present invention, the system includes a light concentration and frequency division subsystem, a three-step methane steam reforming subsystem, a high-temperature water electrolysis hydrogen production subsystem, and a heat exchange subsystem.

[0029] The focusing and frequency division subsystem divides the solar spectrum into a first light beam and a second light beam through a solar focusing and frequency division device 1, wherein the wavelength range of the second light beam is preferably 600-900nm short wave for power generation, and the wavelength range of the first light beam includes the remaining bands for heat collection; the electric energy generated by power generation is used to drive the SOEC water electrolysis H2 subsystem, and the heat energy generated by heat collection is used to drive the three-step methane steam reforming subsystem.

[0030] The three-step methane steam reforming subsystem includes a heat collection unit (not shown in the figure), and a reforming reaction unit, wherein the heat collection unit converts the first light beam into thermal energy; the reforming reaction unit is used to perform a three-step methane steam reforming reaction, specifically including a reduction reactor 3, an oxidation reactor 4 and a reoxidation reactor 5, wherein:

[0031] The reduction reactor 3 is thermally connected to the heat collection unit. In the reduction reactor 3, methane and oxygen carrier MO z The MO z Restore to MO x , and generate products such as CO, H2, CO2, H2O, etc., among which CO and H2 are hydrocarbon fuels, which can be used for Fischer-Tropsch synthesis, and oxygen carrier MO z One or more selected from cerium oxide, zinc oxide, copper oxide, nickel oxide or perovskite-type oxygen carriers.

[0032] In the oxidation reactor 4, water vapor and oxygen carrier MO x The oxygen carrier MO xInitial oxidation to MO y , and generate hydrogen. The initial oxidation degree of the oxygen carrier can be adjusted by changing the amount of water vapor. The reaction in the oxidation reactor 4 is an exothermic reaction, so there is no need for a heat collection unit to drive it at high temperature.

[0033] In the reoxidation reactor 5, the oxygen carrier MO y React with oxygen to convert oxygen carrier MO y Completely oxidized to MO z The reaction in the reoxidation reactor 5 is an exothermic reaction, so there is no need for a heat collection unit to drive it at a high temperature. Preferably, the reoxidation reactor 5 and the reduction reactor 4 are thermally connected to transfer the residual heat of the reaction in the reoxidation reactor 5 to the reduction reactor 4.

[0034] The reduction reactor 3 is connected to the oxidation reactor 4 to transport MO x , the oxidation reactor 4 is connected to the reoxidation reactor to deliver MO to the reoxidation reactor 5 y , the reoxidation reactor 5 is connected to the reduction reactor to deliver MO to the reduction reactor 3 z， , completing the thermochemical cycle process, making the unit oxygen carrier MO z Can react with more methane. Wherein, the connection mode between each reactor can be pipeline connection, of course not limited to this.

[0035] The high-temperature water electrolysis hydrogen production subsystem includes a solid oxide electrolysis cell (SOEC) 6 and a photovoltaic power generation unit, wherein the photovoltaic power generation unit includes a photovoltaic cell 10, which converts the second light beam into electrical energy. The spectrum can be efficiently utilized to improve the power generation efficiency of photovoltaic cells. The solid oxide electrolytic cell 6 has a conventional structure in the art, for example, mainly composed of a porous anode, a solid electrolyte and a porous cathode, and is used for high-temperature steam electrolysis to produce hydrogen, and the reaction temperature is generally between 800 and 950°C. Wherein:

[0036] The solid oxide electrolytic cell 6 is connected to the photovoltaic cell 10 to utilize the electrical energy of the photovoltaic cell 10. Conducting an electrolytic hydrogen production reaction;

[0037] The solid oxide electrolytic cell 6 is also thermally connected to the oxidation reactor 4, transferring heat from the oxidation reactor 4. To the solid oxide electrolysis cell 6, using water vapor and oxygen carrier MO x The waste heat of the reaction is used for electrolysis to produce hydrogen;

[0038] The solid oxide electrolytic cell 6 is also connected to the reoxidation reactor 5 via a pipeline to deliver oxygen carrier MO to the reoxidation reactor. yThe oxygen required for complete oxidation is further provided on the pipeline with a flow divider to deliver part of the oxygen generated in the solid oxide electrolysis cell 6 to the reoxidation reactor 5;

[0039] The solid oxide electrolysis cell 6 is also connected to the oxidation reactor 4 by a pipeline so as to introduce a mixture of hydrogen output from the oxidation reactor and unreacted water vapor, wherein the unreacted water vapor serves as a raw material for hydrogen production by electrolysis, thereby increasing the amount of water decomposition, and the hydrogen provides a reducing atmosphere for the porous cathode to protect, thereby improving the efficiency and effect of hydrogen production by electrolysis.

[0040] The heat exchange subsystem is connected to the reforming reaction unit and the solid oxide electrolysis cell through pipelines to recover the heat of hydrocarbon fuel, hydrogen and unreacted water vapor output by the reforming reaction unit, and hydrogen and incompletely electrolyzed water vapor output by the solid oxide electrolysis cell; further, it uses the recovered heat to preheat the methane and water vapor required by the reforming reaction unit. As an example, the heat exchange subsystem includes a first heat exchanger 2, a second heat exchanger 7, a third heat exchanger 8 and a fourth heat exchanger 9, wherein:

[0041] The first heat exchanger 2 exchanges heat between the room temperature methane and the hydrocarbon fuel output from the reduction reactor 3 to complete the preheating of the methane;

[0042] The second heat exchanger 7 exchanges heat between the normal temperature water and the hydrocarbon fuel after passing through the first heat exchanger 2 to complete the primary preheating of the water vapor;

[0043] The third heat exchanger 8 exchanges heat with the water vapor after passing through the second heat exchanger 7, the hydrogen output from the solid oxide electrolysis cell 6, and the water vapor that is not completely electrolyzed, thereby completing the secondary preheating of the water vapor;

[0044] The fourth heat exchanger 9 exchanges heat with the water vapor after passing through the third heat exchanger and the mixed gas of hydrogen output from the oxidation reactor and unreacted water vapor to complete the three-stage preheating of the water vapor. The mixed gas after passing through the fourth heat exchanger 9 is introduced into the solid oxide electrolytic cell to make the temperature of the electrolytic hydrogen production reaction lower than that of the water vapor and the oxygen carrier MO. x The reaction temperature is set so that the heat from the oxidation reactor 4 can be smoothly transferred to the solid oxide electrolysis cell.

[0045] The present invention also provides a method for preparing fuel using the solar fuel preparation system as described above, comprising:

[0046] Step 1: Concentrate and divide the solar spectrum to form a first light beam and a second light beam, wherein the first light beam is converted into thermal energy and the second light beam is converted into electrical energy;

[0047] Step 2: Using the heat energy to carry out a three-step methane steam reforming reaction with methane, water vapor and oxygen carrier as raw materials to obtain hydrocarbon fuel and hydrogen, and recovering the heat of the hydrocarbon fuel, hydrogen and unreacted water vapor, wherein the three-step methane steam reforming reaction includes: oxygen carrier MO z Reacts with methane to generate hydrocarbon fuel and oxygen carrier MO x , water vapor and the oxygen carrier MO x Reaction to generate MO y and hydrogen, and the oxygen carrier MO y Reacts with oxygen to form oxygen carrier MO z ;

[0048] Step 3: Passing a mixture of hydrogen and unreacted water vapor into a solid oxide electrolysis cell, using the electrical energy as well as water vapor and oxygen carrier MO x The waste heat of the reaction is used for electrolysis to produce hydrogen to obtain hydrogen fuel and oxygen, and the heat of the hydrogen output by the solid oxide electrolysis cell and the incompletely electrolyzed water vapor is recovered;

[0049] Step 4: Use the oxygen obtained in step 3 as a raw material and the oxygen carrier MO in step 2 y Reaction to generate oxygen carrier MO z .

[0050] The method further includes the step of using the heat recovered in steps 2 and 3 to preheat the methane and water vapor introduced into the reforming reaction unit, specifically including: exchanging heat between the hydrocarbon fuel and methane at room temperature to complete the preheating of methane; exchanging heat between the hydrocarbon fuel after the heat exchange and water at room temperature to complete the primary preheating of water vapor; exchanging heat between the water vapor after the primary preheating and the hydrogen and the water vapor that is not completely electrolyzed to complete the secondary preheating of water vapor; exchanging heat between the water vapor after the secondary preheating and the mixed gas to complete the tertiary preheating of water vapor.

[0051] The heat exchanger is used to heat the methane to a temperature that reaches the oxygen carrier MO z The temperature required for the reaction with methane; through heat exchange, the temperature of the water vapor is made as close as possible to the temperature of the water vapor and the oxygen carrier MO x The reaction temperature required; the oxygen carrier MO x The temperature is kept constant during the oxidation reaction with water vapor.

[0052] The following will be combined with the preferred embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0053] Example 1

[0054] 1. System process description and effect analysis

[0055] In this embodiment, CH4 at room temperature is 82.0m 3 / min flow rate in heat exchanger 2 and the product flow of reduction reactor 3 to complete preheating. After preheating, CH4 enters reduction reactor 3 and reacts with oxygen carrier CeO2 in the reactor to generate CO, H2, CO2, H2O, CeO 1.8 Before entering the oxidation reactor 3 at a rate of 147.9 L / min, the room temperature H2O is first preheated in the heat exchanger 7 with the product flow of the reduction reactor 3 passing through the heat exchanger 2, and then in the heat exchanger 8 with the product flow of the solid oxide electrolysis cell 6 to complete the secondary preheating, and then in the heat exchanger 9 with the product flow of the oxidation reactor 4 to complete the tertiary preheating and enter the oxidation reactor 4, and with the CeO 1.8 The reaction produces CeO 1.951 The H2 in the oxidation reactor 4 and the unreacted H2O enter the solid oxide electrolysis cell 6 at a certain flow rate for electrolysis, and the H2O is electrolyzed into H2 and O2. The heat energy and electric energy for the solid oxide electrolysis cell 6 to electrolyze water to produce hydrogen come from the oxidation reactor 4 and the photovoltaic cell 10 respectively. The electrolysis product O2 in the solid oxide electrolysis cell 6 enters the oxidation reactor 4 and CeO2 through the diverter 11 at a certain flow rate. 1.951 The reaction generates CeO2, which leaves the reoxidation reactor 4 and returns to the reduction reactor 3.

[0056] 2. Basic system parameters

[0057] According to references, the optical efficiency of sunlight concentration and frequency division is about 70% (effective solar energy after concentration and frequency division is 70% of all incident sunlight), of which 20.5% of the solar spectrum is used for PV cell power generation, and 49.6% of the solar spectrum is used to provide the heat required for methane chemical chain reforming. Silicon photovoltaic cells with mature technology are selected for power generation, and the effective spectrum wavelength range is 600-900nm. The photovoltaic power generation efficiency in this wavelength range is 60%. The remaining sunlight spectrum is used for heat collection, and the light-to-heat collection efficiency is 70%. The heat exchange efficiency of the heat exchanger of the present invention is 1, the average temperature of each reactor is shown in Table 1, the temperature of each logistics of the system and the total flow rate are shown in Table 2, and the system operates at normal pressure.

[0058] Table 1. Average temperature of each reactor in the system

[0059] Reactor Name Temperature T(℃) Reduction reactor 3 950 Oxidation reactor 4 950 Reoxidation reactor 5 960 Solid oxide electrolysis cell 6 940

[0060] Table 2. Temperature and flow of each logistics system

[0061]

[0062] The calculation results show that when the total energy of sunlight input is 55635.0kW, 27595.0kW of spectral energy is used for concentrating and collecting heat, which is converted into usable heat energy. 19316.5kW, 11405.2kW of spectral energy is used for photovoltaic power generation and converted into electrical energy The system produces syngas at a rate of 652.7 kmol / h, of which CO is 214.5 kmol / h and H2 is 429.7 kmol / h. The system decomposes water to produce pure H2 at a rate of 325.0 kmol / h. The efficiency of solar energy conversion into fuel is η sol-fuel It can reach 42.1%.

[0063] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A solar fuel preparation system coupled with an electric-thermal-chemical cycle, comprising: A light-concentrating and frequency-dividing subsystem, which concentrates and divides the solar spectrum to form a first light beam and a second light beam; The three-step methane steam reforming subsystem includes: a heat collection unit, which converts the first light beam into heat energy; and Reforming reaction unit, comprising: Reduction reactor, thermally connected to the heat collection unit, as an oxygen carrier MO z Reacts with methane to generate hydrocarbon fuel and oxygen carrier MO x Container; Oxidation reactor, MO as water vapor and oxygen carrier x Reaction to generate MO y and hydrogen gas containers, and Reoxidation reactor, MO as oxygen carrier y Reacts with oxygen to form oxygen carrier MO z Container, The reduction reactor is connected to the oxidation reactor to deliver MO to the oxidation reactor x , the oxidation reactor is connected to the reoxidation reactor to deliver MO to the reoxidation reactor y , the reoxidation reactor is connected to the reduction reactor to deliver MO to the reduction reactor z ; High-temperature water electrolysis hydrogen production subsystem, including: a photovoltaic power generation unit, converting the second light beam into electrical energy; and A solid oxide electrolysis cell is electrically connected to the photovoltaic power generation unit and thermally connected to the oxidation reactor, and serves as a container for generating hydrogen fuel by electrolyzing water vapor under the action of heat transferred from the oxidation reactor; the solid oxide electrolysis cell is also connected to the reoxidation reactor and the oxidation reactor, respectively, so as to transport oxygen to the reoxidation reactor and pass a mixed gas of hydrogen output from the oxidation reactor and unreacted water vapor into the solid oxide electrolysis cell; the reaction temperature of the water vapor electrolyzing hydrogen to generate hydrogen is 800-950°C; and a heat exchange subsystem, connected to the reforming reaction unit and the solid oxide electrolysis cell through pipelines, respectively, to recover the heat of the hydrocarbon fuel, hydrogen and unreacted water vapor output by the reforming reaction unit, and the hydrogen and incompletely electrolyzed water vapor output by the solid oxide electrolysis cell; The heat exchange subsystem specifically includes: A first heat exchanger is used to perform heat exchange between room temperature methane and the hydrocarbon fuel output from the reduction reactor to complete the preheating of methane; The second heat exchanger is used to exchange heat between the normal temperature water and the hydrocarbon fuel after passing through the first heat exchanger to complete the primary preheating of the water vapor; A third heat exchanger is used to exchange heat between the water vapor after passing through the second heat exchanger and the hydrogen output from the solid oxide electrolysis cell and the water vapor that is not completely electrolyzed, so as to complete the secondary preheating of the water vapor; and The fourth heat exchanger is used to exchange heat between the water vapor after passing through the third heat exchanger and the mixed gas of the hydrogen output from the oxidation reactor and the unreacted water vapor, so as to complete the three-stage preheating of the water vapor; The reoxidation reactor is thermally connected to the reduction reactor to transfer heat to the reduction reactor.

2. The solar fuel preparation system according to claim 1, characterized in that: The fourth heat exchanger is also connected to the solid oxide electrolysis cell so as to pass the mixed gas of hydrogen and unreacted water vapor after passing through the fourth heat exchanger into the solid oxide electrolysis cell.

3. The solar fuel preparation system according to claim 1, characterized in that: The oxygen carrier MO z One or more selected from cerium oxide, zinc oxide, copper oxide, nickel oxide or perovskite-type oxygen carriers.

4. The solar fuel preparation system according to claim 1, characterized in that: Said A photovoltaic power generation unit includes photovoltaic cells.

5. The solar fuel preparation system according to claim 1, characterized in that: A flow divider is provided on the pipeline between the solid oxide electrolysis cell and the reoxidation reactor to transport part of the oxygen generated by the solid oxide electrolysis cell to the reoxidation reactor; The spectrum with a wavelength range of 600-900 nm in the solar spectrum is used as the second light beam, and the spectrum with the remaining wavelengths in the solar spectrum is used as the first light beam.

6. A method for preparing fuel using the solar fuel preparation system according to any one of claims 1 to 5, comprising: Step 1: Concentrate and divide the solar spectrum to form a first light beam and a second light beam, wherein the first light beam is converted into thermal energy and the second light beam is converted into electrical energy; Step 2: utilizing the heat energy to carry out a three-step methane steam reforming reaction with methane, water vapor and oxygen carrier as raw materials to obtain hydrocarbon fuel and hydrogen, and recovering the heat of the hydrocarbon fuel, hydrogen and unreacted water vapor, wherein the three-step methane steam reforming reaction comprises: Oxygen carrier MO z Reacts with methane to generate hydrocarbon fuel and oxygen carrier MO x , water vapor and the oxygen carrier MO x Reaction to generate MO y and hydrogen, and the oxygen carrier MO y Reacts with oxygen to form oxygen carrier MO z ; Step 3: Passing a mixture of hydrogen and unreacted water vapor into a solid oxide electrolysis cell, Using the electrical energy as well as water vapor and oxygen carrier MO x The waste heat of the reaction is used for electrolysis to produce hydrogen to obtain hydrogen fuel and oxygen, and the heat of the hydrogen output by the solid oxide electrolysis cell and the incompletely electrolyzed water vapor is recovered; Step 4: Use the oxygen obtained in step 3 as raw material and the oxygen carrier MO in step 2 y Reaction to generate oxygen carrier MO z .

7. The method according to claim 6, characterized in that The method further comprises the step of preheating the methane and water vapor introduced into the reforming reaction unit using the heat recovered in steps 2 and 3, specifically comprising: Exchanging heat between the hydrocarbon fuel and methane at room temperature to complete preheating of the methane; The hydrocarbon fuel after heat exchange is exchanged with water at room temperature to complete the primary preheating of water vapor; Exchanging heat between the primary preheated water vapor and the hydrogen and the incompletely electrolyzed water vapor to complete the secondary preheating of the water vapor; The water vapor after the secondary preheating is heat exchanged with the mixed gas to complete the tertiary preheating of the water vapor.

8. The method according to claim 7, characterized in that The mixed gas after heat exchange is introduced into the solid oxide electrolysis cell to make the temperature of the electrolysis hydrogen production reaction lower than that of water vapor and oxygen carrier MO. x The temperature of the reaction.

9. The method according to claim 7, characterized in that: The temperature of methane reaches the oxygen carrier MO by heat exchange z The temperature required for the reaction with methane; The water vapor temperature is raised by heat exchange to reach the temperature of the oxygen carrier MO x The temperature required for the reaction; The oxygen carrier MO x The temperature is kept constant during the oxidation reaction with water vapor.

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