Multistage condensation frequency division driving magnesium-chlorine circulation hydrogen production system

Abstract

The invention discloses a multistage condensation frequency division magnesium-chlorine cycle hydrogen production system, the system comprises a solar full-spectrum multistage condensation frequency division utilization subsystem and a magnesium-chlorine cycle hydrogen production subsystem, the solar full-spectrum multistage condensation frequency division utilization subsystem carries out solar multispectral condensation with different multiples, converts a photovoltaic available spectrum into electric energy, and carries out hydrogen-chlorine cycle hydrogen production on the magnesium-chlorine cycle hydrogen production subsystem, and the magnesium-chlorine cycle hydrogen production subsystem carries out hydrogen-chlorine cycle hydrogen production on the magnesium-chlorine cycle hydrogen production subsystem. The residual spectrum generates heat energy at different temperatures by utilizing a radiation absorber, so that full-spectrum utilization of solar energy is realized. And the magnesium-chlorine circulating hydrogen production subsystem is used for carrying out three-step magnesium-chlorine circulating reaction hydrogen production by utilizing the electric energy generated by the photovoltaic power generation assembly and the heat energy at different temperatures generated by different radiation absorbers, and the magnesium-chlorine circulating net reaction is that water is decomposed into hydrogen and oxygen. According to the energy requirement and energy quality matching principle of the whole process, solar radiation energy is reasonably adjusted through multi-stage light condensation frequency division, so that three-step magnesium-chlorine thermochemical cycle conversion is driven in a stepped mode, and stepped ordered conversion hydrogen production of solar energy is achieved.

Description

Technical Field

[0001] This invention belongs to the field of new energy preparation technology of energy quality cascade utilization, specifically involving a multi-stage concentrated light frequency division driven magnesium-chlorine cycle hydrogen production system. Background Technology

[0002] Faced with increasingly severe environmental problems and energy crises, developing clean, green, and sustainable energy sources is becoming increasingly important. Hydrogen, as a zero-carbon energy source, is considered key to achieving a low-carbon energy transition due to its high calorific value (hydrogen 141.9 MJ / kg, petroleum 47.5 MJ / kg, natural gas 55.5 MJ / kg). Currently, the vast majority of global hydrogen production comes from fossil fuels, with less than 1% coming from renewable energy sources. Solar energy, as a green and clean renewable energy source, has a massive total volume. Solar-powered hydrogen production not only converts unstable and intermittent solar energy into stable chemical energy in hydrogen for storage but is also very environmentally friendly, making it a promising technological route for green hydrogen production.

[0003] Currently, solar-powered hydrogen production technologies can be categorized into three types: utilizing solar energy in the form of photons, including photocatalysis and photoelectrochemical methods; converting solar energy into electrons, including photovoltaic-electrochemical methods; and converting solar energy into heat, including solar thermochemical hydrogen production and solar photothermal hydrogen production. Among these, photothermal chemical water splitting involves coupling a thermochemical cycle with solar energy. Thermochemical cycle hydrogen production technology is mature and diverse, and solar power generation technology has a high degree of commercialization, making it of great significance in practical applications. Thermochemical cycles involve stepwise heating and decomposition through multiple chemical reactions, ultimately forming a complete cycle that decomposes water into H2 and O2, significantly reducing the temperature at which water molecules decompose. In this closed loop, the only raw material is water, and the reactants and products at each step can be recycled, avoiding greenhouse gas emissions and having low dependence on catalysts. Furthermore, H2 and O2 are generated in different reaction steps, eliminating the need for complex separation processes.

[0004] Magnesium-chlorine cycle hydrogen production is a thermochemical cycle method. The Mg-Cl cycle consists of three steps: hydrolysis reaction: MgCl2(s) + H2O(g) → MgO(s) + 2HCl(g), chlorination reaction: MgO(s) + Cl2(g) → MgCl2(s) + 0.5O2(g), and electrolysis reaction: 2HCl(g) → H2(g) + Cl2(g). Each reaction requires thermal energy and electrical energy at different temperatures (90-550℃), which makes it difficult to achieve efficient coupling between the Mg-Cl cycle system and a solar energy utilization system. Summary of the Invention

[0005] Based on the advantages and shortcomings of the aforementioned technologies, this application aims to provide a multi-stage concentrating and frequency-dividing driven magnesium-chlorine cycle hydrogen production system. This invention, based on the principle of energy quality matching, constructs a solar multi-stage concentrating and frequency-dividing energy conversion hydrogen production system. Utilizing concentrating modules, frequency-dividing modules, photovoltaic power generation modules, radiation absorbers, thermal storage modules, heat exchange modules, and a magnesium-chlorine cycle thermochemical reaction device, an energy quality-matched coupled hydrogen production system is constructed, which can improve energy conversion efficiency.

[0006] To address the technical challenges, this invention proposes a multi-stage concentrated light frequency division driven magnesium-chlorine cycle hydrogen production system, which includes a solar full-spectrum multi-stage concentrated light frequency division utilization subsystem and a magnesium-chlorine cycle hydrogen production subsystem. The solar full-spectrum multi-stage concentrating and frequency-dividing utilization subsystem includes a two-stage solar spectrum concentrator, a frequency-dividing module, a radiation absorber, a photovoltaic power generation module, a battery, a thermal storage module, and a heat exchange module; the magnesium-chlorine cycle hydrogen production subsystem includes a magnesium-chlorine cycle hydrogen production reactor; The two-stage solar concentrator concentrates sunlight with two different concentration ratios. The concentrated beams with different concentration ratios are divided by two frequency-dividing components. The usable photovoltaic light energy after frequency division enters the photovoltaic power generation module to generate photovoltaic power, while the remaining light energy enters two radiation absorbers according to the concentration ratio and produces heat energy at different temperatures. The battery is used to store the electrical energy generated by the photovoltaic power generation module. The heat storage component uses its internal heat storage medium to store a portion of the heat generated by the radiation absorber. The heat exchanger component is used to perform heat exchange between different radiation absorbers and reactants in the magnesium-chlorine cycle hydrogen production subsystem. The magnesium-chlorine cycle hydrogen production reactor includes a hydrolysis reactor for hydrolysis, a chlorination reactor for chlorination, and an electrolysis reactor for electrolysis. The magnesium-chlorine cycle hydrogen production reactor utilizes electrical energy generated by photovoltaic power generation components and thermal energy at different temperatures generated by different radiation absorbers to carry out the magnesium-chlorine cycle reaction. The net reaction is the decomposition of water into hydrogen and oxygen.

[0007] According to a preferred embodiment of the present invention, the solar spectrum multi-stage concentrating module includes a first-stage medium-power concentrating module and a second-stage high-power concentrating module; The first-stage medium-concentration module provides a concentration ratio of 495 to 505 times. The resulting concentrated beam enters the medium-concentration frequency divider for spectral frequency division. The usable photovoltaic band light energy is used for photovoltaic power generation, and the remaining band light energy enters the medium-temperature radiation absorber to heat the chlorine gas, the raw material for the chlorination reaction in the magnesium-chlorine cycle hydrogen production reactor, and preheat the heat storage medium in the medium-temperature heat storage module. The second-stage high-concentration module provides a concentration ratio of 595 to 605 times. The resulting concentrated beam enters the high-concentration frequency division module for spectral frequency division. Part of the frequency-divided light energy is used for photovoltaic power generation, and the remaining light energy enters the high-temperature radiation absorber to heat the temperature required for the hydrolysis reaction in the magnesium-chlorine cycle hydrogen production reactor and preheat the heat storage medium in the high-temperature heat storage module. The photovoltaic cell module's storage battery is used to power the electrolysis reaction in the magnesium-chlorine cycle hydrogen production reactor; the photovoltaic power generation module has a photovoltaic cell waste heat utilization device, which recovers the heat energy of the photovoltaic power generation module to preheat hot water as a raw material for thermochemical reactions, while avoiding the temperature rise of the photovoltaic cell due to a large amount of radiation energy.

[0008] Compared with the prior art, the present invention has the following beneficial effects: The concentrating photovoltaic (PV) module of this invention is designed with different concentration ratios based on the varying thermal energy temperatures required for each step of the subsequent coupled magnesium-chlorine cycle. It includes a first-stage medium-concentration PV module and a second-stage high-concentration PV module. The concentrated beam obtained from the first-stage medium-concentration PV module enters a medium-concentration frequency divider for spectral frequency division. A portion of the light energy in one wavelength band is used for photovoltaic power generation, while the remaining light energy enters a medium-temperature radiation absorber to heat the raw material (Cl2) for the chlorination reaction. Similarly, the concentrated beam obtained from the second-stage high-concentration PV module enters a high-concentration frequency divider for spectral frequency division. A portion of the light energy in one wavelength band is used for photovoltaic power generation, while the remaining light energy enters a medium-high temperature radiation absorber to heat the hydrolysis reaction within the hydrolysis reactor, which requires high thermal energy. The electricity generated by the photovoltaic module is used to power the electrolysis reaction within the electrolysis reactor. The thermal storage component stores some of the heat generated by the radiation absorber when there is sufficient solar energy input, and provides heat when there is insufficient solar energy input, in order to balance the instability of solar energy and ensure the stable operation of the system day and night; The magnesium-chlorine cycle hydrogen production reactor utilizes thermal energy obtained from different concentration ratios and frequency divisions, as well as photovoltaic power generation to drive the three steps in the cycle, so that the energy input to the reaction cycle matches the energy quality required for the reaction, producing hydrogen and oxygen.

[0009] This invention achieves decoupling of solar radiation energy of different qualities through multi-stage concentrating and frequency division, and then converts it into electrical / thermal energy coupling of different energy qualities to drive Mg-Cl cycle hydrogen production, realizing the cascaded and orderly conversion of solar energy, which is in line with the thermodynamic principle of energy cascade utilization.

[0010] Based on the different energy quality of the thermal energy required by the thermochemical cycle, this invention obtains thermal energy at different temperatures after frequency division by using different concentration ratios, which is used to drive the hydrolysis and chlorination steps of the thermochemical cycle; at the same time, the photovoltaic cells can use the radiant energy of the spectrum to generate photovoltaic power, producing high-quality electrical energy, which is then used to drive the electrolysis step of the thermochemical cycle.

[0011] This invention balances the instability of solar energy by incorporating a thermal storage device, ensuring the system's self-sustaining operation day and night. The electro / thermal coupling-driven thermochemical cycle for hydrogen production enables the cascade conversion and high-quality storage of solar energy, without consuming any fossil fuels or producing any greenhouse gases.

[0012] All the energy used in the reaction of this invention system comes from solar energy, and the development of hydrogen energy using solar energy helps to transform the energy structure.

[0013] The energy supply of the hydrogen production system coupled in this invention should be completed by multiple solar full-spectrum multi-level concentrating frequency division systems equipped with different frequency division components, photovoltaic cells and concentrating components. It can achieve efficient energy cascade conversion under low concentration ratio conditions, reduce the complexity and cost of the concentrating system, improve the application potential, and the total solar hydrogen production efficiency can exceed 55%. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of a multi-stage concentrated light frequency division driven magnesium-chlorine cycle hydrogen production system proposed in this invention.

[0015] Among them, 1a~first-stage medium-concentrating photovoltaic module, 1b~second-stage high-concentrating photovoltaic module, 2a~medium-concentrating photovoltaic frequency divider module, 2b~high-concentrating photovoltaic frequency divider module, 3a~medium-temperature radiation absorber, 3b~medium-high-temperature radiation absorber, 4a~photovoltaic cell, 4b~photovoltaic cell waste heat utilization device, 5~storage battery, 6a~medium-temperature thermal storage module, 6b~medium-high-temperature thermal storage module, 7a~medium-temperature molten salt heat exchanger, 7b~medium-high-temperature molten salt heat exchanger, 7c~first-stage water heat exchanger, 7d~second-stage water heat exchanger, 7e~third-stage water heat exchanger, 7f~magnesium compound heat exchanger, 7g~first-stage chlorine heat exchanger and 7h~second-stage chlorine heat exchanger;), 8~magnesium-chlorine cycle hydrogen production system (8a~hydrolysis reactor, 8b~chlorination reactor, 8c~electrolysis reactor, 9~hydrogen storage tank, 10~oxygen storage tank). Detailed Implementation

[0016] To better understand the technical solution of this application, the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0017] The technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention and are intended to explain the inventive concept. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] Unless otherwise expressly specified and limited, the terms “high magnification,” “medium magnification,” “high temperature,” “medium temperature,” etc., used in descriptions are used only to describe relative characteristics and do not indicate or imply that the technical characteristics referred to must have specific indicators.

[0019] Unless otherwise expressly specified and limited, the terms “primary,” “secondary,” “first-level,” “second-level,” etc., used in the description are for descriptive purposes only, in order to distinguish similar components or devices with different purposes and functions, and shall not be construed as indicating or implying relative importance or implicitly specifying the technical features indicated.

[0020] Unless otherwise explicitly specified and limited, the terms "connected" and "linked" used in the description should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments according to the specific circumstances.

[0021] This application provides a multi-stage concentrated light frequency division driven magnesium-chlorine cycle hydrogen production system, and a coupling method for using this system to produce hydrogen.

[0022] See Figure 1 In one specific embodiment of this application, a multi-stage concentrated light frequency division driven magnesium-chlorine cycle hydrogen production system is provided, including a solar full-spectrum multi-stage concentrated light frequency division utilization subsystem and a magnesium-chlorine cycle hydrogen production subsystem; like Figure 1 As shown, in one embodiment of the present invention, the solar full-spectrum multi-stage concentrating and frequency-dividing utilization subsystem includes a two-stage solar spectrum concentrator, a frequency-dividing component, a radiation absorber, a photovoltaic power generation component, a battery 5, a thermal storage component, and a heat exchange component. The magnesium-chlorine cycle hydrogen production subsystem includes a magnesium-chlorine cycle hydrogen production reactor; The working principle of the solar full-spectrum multi-stage concentrating and frequency-dividing utilization subsystem is as follows: the two-stage solar concentrator concentrates sunlight with two different concentration ratios, and the concentrated beams with different concentration ratios are divided by two frequency-dividing components. The usable photovoltaic bands of light energy after frequency division enter the photovoltaic power generation module for photovoltaic power generation, while the remaining bands of light energy enter two radiation absorbers according to the concentration ratio and produce heat energy at different temperatures. The battery is used to store the electrical energy generated by the photovoltaic power generation module. The thermal storage component stores a portion of the heat generated by the radiation absorbers when solar energy input is sufficient, and provides heat to the heat exchanger components when solar energy input is insufficient, in order to balance the instability of solar energy and ensure stable operation of the system day and night.

[0023] In one specific embodiment of the present invention, the two-stage solar spectral concentrator is designed with different concentration ratios according to the different thermal energy temperatures required for each step of the subsequent coupled magnesium-chlorine cycle. It includes a first-stage medium-concentration concentrator 1a and a second-stage high-concentration concentrator 1b. The first-stage medium-concentration concentrator 1a uses a dish or tower concentrator to provide a concentration ratio of 495-505 times, depending on the scale. The resulting concentrated beam enters a medium-concentration frequency divider 2a for spectral frequency division. Part of the light energy in one wavelength band is used for power generation in the photovoltaic cell 4a, and the remaining light energy enters a medium-temperature radiation absorber 3b to heat the raw material (Cl2) for the chlorination reaction. The second-stage high-concentration concentrator 1b uses a dish or tower concentrator to provide a concentration ratio of 595-605 times, depending on the scale. The resulting concentrated beam enters a high-concentration frequency divider 2b for spectral frequency division. Part of the light energy in one wavelength band is used for power generation in the photovoltaic cell 4a, and the remaining light energy enters a medium-high temperature radiation absorber 3b to heat the hydrolysis reaction in the hydrolysis reactor 6a, which has high thermal energy requirements. The photovoltaic power generation module has a photovoltaic cell waste heat utilization device 4b, which recovers the heat energy of the photovoltaic cell 4a to preheat hot water as a raw material for thermochemical reaction, while avoiding the temperature rise of the photovoltaic cell due to a large amount of radiation energy.

[0024] The frequency division component of this invention is an optical interference multilayer frequency division film formed by alternating deposition of TiO2 and SiO2 materials on a transparent substrate. The frequency division component includes a medium-concentration frequency division component 2a and a high-concentration frequency division component 2b. It is an optical interference multilayer frequency division film formed by alternating deposition of TiO2 and SiO2 materials on a transparent substrate, used to achieve selective transmission of the solar spectrum. The medium-concentration frequency division component 2a transmits the wavelength band of 390nm~670nm to the photovoltaic cell module below for power generation, and the remaining wavelength band enters the medium-temperature radiation absorber 3a and is converted into heat energy. The high-concentration frequency division component 2b transmits the wavelength band of 480nm~630nm to the photovoltaic power generation module below for power generation, and the remaining wavelength band enters the high-temperature radiation absorber 3b and is converted into heat energy. In one specific embodiment of the present invention, the medium-concentration frequency divider component 2a can transmit light in the 390-670nm wavelength band. Its structure consists of five layers: the first layer is SiO2 with a thickness of 55nm, the second layer is TiO2 with a thickness of 560nm, the third layer is SiO2 with a thickness of 10nm, the fourth layer is TiO2 with a thickness of 15nm, and the fifth layer is SiO2 with a thickness of 95nm. The high-concentration frequency divider component 2b can transmit light in the 480-630nm wavelength band. Its structure consists of six layers: the first layer is TiO2 with a thickness of 110nm, the second layer is SiO2 with a thickness of 135nm, the third layer is TiO2 with a thickness of 135nm, the fourth layer is TiO2 with a thickness of 15nm, and the fifth layer is SiO2 with a thickness of 95nm. The first layer is made of TiO2 with a thickness of 110 nm, the fourth layer is made of SiO2 with a thickness of 135 nm, the fifth layer is made of TiO2 with a thickness of 55 nm, and the sixth layer is made of SiO2 with a thickness of 20 nm. The frequency-dividing film used has good transmission characteristics (>0.9) for the available spectrum of the photovoltaic cell, which is used to achieve selective transmission of the solar spectrum. The unavailable spectrum is called the residual light spectrum. The frequency divider has good reflection characteristics (>0.9) for the residual light spectrum. The optical characteristics of the frequency-dividing component can be designed and adjusted according to the spectral response characteristics of the photovoltaic cell used. The radiation absorber component can efficiently convert light energy into heat energy with minimal loss.

[0025] The electricity generated by the photovoltaic cell module is stored in the battery 5 and used to power the electrolytic reaction in the electrolysis reactor 6c. The photovoltaic cell waste heat utilization device 4b recovers the heat energy of the photovoltaic cell 4a to preheat the water as a raw material for the thermochemical reaction, while avoiding the temperature rise of the photovoltaic cell due to a large amount of radiation energy. Preferably, the photovoltaic cell is a Si polyphotovoltaic cell. High bandgap cells have lower power generation and larger energy in the residual light spectrum compared to low bandgap cells. Therefore, when using low bandgap cells, the electrical energy supplied to the system increases, and the concentration of residual light spectrum can be enhanced to ensure that the heat energy supplied to the system meets the requirements.

[0026] The thermal storage component 6 of this invention is used to store a portion of the heat generated by the radiation absorber when solar energy input is sufficient, and to provide heat when solar energy input is insufficient, in order to balance the instability of solar energy and ensure stable operation of the system day and night. Preferably, in a specific embodiment of this invention, the thermal storage component includes a medium-temperature thermal storage component 6a and a medium-high temperature thermal storage component 6b, which use different thermal storage media according to different temperatures. The operating temperature of the medium-temperature thermal storage component 6a is 500°C, and the operating temperature of the medium-high temperature thermal storage component 6b is 550°C. Both adopt molten salt thermal storage, and the medium composition is KCl and MgCl2. The power distribution ratio between the two is 9:1. The heat transfer medium between the radiation absorber, the thermal storage component, and the heat exchange component includes, but is not limited to, air and carbon dioxide. In this embodiment, it is air.

[0027] like Figure 1 As shown, in one embodiment of the present invention, the magnesium-chlorine cycle hydrogen production subsystem includes a magnesium-chlorine cycle hydrogen production reactor; wherein, the magnesium-chlorine cycle hydrogen production reactor includes a hydrolysis reactor 8a, a chlorination reactor 8b, and an electrolysis reactor 8c. Figure 1 As shown, optionally, the system of the present invention further includes a hydrogen storage tank 9 and an oxygen storage tank 10, wherein the hydrogen storage tank 9 is used to collect H2 generated by the electrolysis reaction of the magnesium-chlorine cycle hydrogen production reaction. The oxygen storage tank 10 is used to collect O2 generated by the pyrolysis reaction in the magnesium-chlorine cycle; The hydrolysis reaction in hydrolysis reactor 8a requires a reaction temperature of 500~550℃. The chemical reaction equation is: MgCl2(s)+H2O(g)→MgO(s)+2HCl(g). The product MgO is fed into chlorination reactor 8b as a raw material, and the product HCl is fed into electrolysis reactor 8c as a raw material. The heat balance required for this step is maintained by the high-concentration heat generated by the high-concentration spectrum of the solar high-concentration system.

[0028] The chlorination reaction in chlorination reactor 8b requires a reaction temperature of 450~500℃. The chemical reaction equation is: MgO(s) + Cl2(g) → MgCl2(s) + 0.5O2(g). The product MgCl2 is fed into hydrolysis reactor 8a as a raw material. The product O2 is stored in oxygen storage tank 10 after exothermic reaction. This step is an exothermic reaction.

[0029] The electrolysis reaction in electrolysis reactor 8c requires a reaction temperature of 90℃. The chemical reaction equation is: 2HCl(g)→H2(g)+Cl2(g). The product is fed into chlorination reactor 8b as a raw material. After the product is exothermic, it is stored in hydrogen storage tank 9. The electrical energy required for this step is provided by the electrical energy stored in battery 5.

[0030] The aforementioned thermochemical reactions constitute a complete cycle, namely the three-step magnesium-chlorine cycle, with the net reaction being the decomposition of water into hydrogen and oxygen. In the magnesium-chlorine cycle hydrogen production reactor, the hydrolysis reaction in the hydrolysis reactor 8a is an endothermic reaction, the chlorination reaction in the chlorination reactor 8b is an exothermic reaction but still requires thermal energy to heat the reactants to the reaction temperature, and the electrolysis reaction in the electrolysis reactor 8c requires electrical energy. The energy quality of the heat and electrical energy required in each step is different. By utilizing the thermal energy obtained from different concentration ratios and frequency divisions, and the electrical energy generated by photovoltaic power generation, the energy driving the three steps in the cycle is matched with the energy quality of the energy input to the reaction cycle, which is beneficial to improving the energy efficiency of the system.

[0031] In one embodiment of the present invention, the three-step magnesium-chlorine cycle products are sequentially connected to a primary water heat exchanger 7a, a secondary water heat exchanger 7b, a tertiary water heat exchanger 7c, a magnesium compound heat exchanger 7d, a primary chlorine heat exchanger 7e, a secondary chlorine heat exchanger 7f, a hydrolysis reactor 8a, a chlorination reactor 8b, and an electrolysis reactor 8c; the inlet of the primary water heat exchanger 7a for hot water is connected to the hot water outlet of the photovoltaic cell preheating and utilization device 4b, and the inlet for H2 is connected to the H2 outlet of the electrolysis reactor 8c; the secondary water heat exchanger 7a... The inlet of the second-stage water heat exchanger 7b, which supplies hot water, is connected to the hot water outlet of the first-stage water heat exchanger 7a. The inlet of the second-stage water heat exchanger 7b, which supplies high-temperature HCl, is connected to the high-temperature HCl outlet of the hydrolysis reactor 8a. The inlet of the third-stage water heat exchanger 7c, which supplies hot water, is connected to the hot water outlet of the second-stage water heat exchanger 7b. The inlet of the magnesium compound heat exchanger 7d, which supplies high-temperature MgO, is connected to the high-temperature MgO outlet of the hydrolysis reactor 6a. The inlet of the medium-temperature MgCl2 heat exchanger 7d is connected to the medium-temperature MgCl2 outlet of the chlorination reactor 8b. The first-stage chlorination heat exchanger 7... The O2 inlet of reactor 8e is connected to the O2 outlet of chlorination reactor 8b, and the Cl2 inlet is connected to the Cl2 outlet of electrolysis reactor 8c; the Cl2 inlet of secondary chlorination heat exchanger 7f is connected to the Cl2 outlet of primary chlorination heat exchanger 7e; hydrolysis reactor 8a has an inlet for hot water, an inlet for medium-temperature MgCl2, and an outlet for high-temperature HCl. The hot water inlet is connected to the hot water outlet of tertiary water heat exchanger 7c, and the medium-temperature MgCl2 inlet is connected to the outlet of magnesium compound heat exchanger 7d. The chlorination reactor 8b is equipped with an inlet for high-temperature MgO, an inlet for Cl2, and an outlet for O2. The inlet for high-temperature MgO is connected to the high-temperature MgO outlet of the magnesium compound heat exchanger 7d, and the inlet for Cl2 is connected to the Cl2 outlet of the secondary chlorination heat exchanger 7f. The electrolysis reactor 8c is equipped with an inlet for high-temperature HCl, an outlet for H2, and an outlet for Cl2. The inlet for high-temperature HCl is connected to the high-temperature HCl outlet of the secondary water heat exchanger 7b.

[0032] In one specific embodiment, the system further includes a solid-liquid material transfer system. This system transports the solid MgO and HCl gas produced in the hydrolysis reactor 8a into the chlorination reactor 8b and the electrolysis reactor 8c, respectively. It also transports the solid MgCl2 produced in the chlorination reactor 8b into the hydrolysis reactor 8a, and the Cl2 gas produced in the electrolysis reactor 8c into the chlorination reactor 8b. The solid-liquid material transfer system recovers and transfers reusable solid and liquid products generated in each device, achieving the recycling of materials in the hydrogen production system, reducing production costs, and avoiding environmental pollution.

[0033] like Figure 1 As shown, in an optional embodiment, the hydrogen storage tank 9 is connected to the H2 outlet of the primary water heat exchanger 7a, and the oxygen storage tank 10 is connected to the O2 outlet of the primary chlorine heat exchanger 7e.

[0034] This application also provides a coupling method for multi-stage concentrated photovoltaic (CPV) frequency division driven magnesium-chlorine cycle hydrogen production, comprising the following steps: CPV modules with different concentration ratios concentrate sunlight, and the resulting concentrated beams are then divided into corresponding frequency division modules. Part of the wavelength is used by photovoltaic power generation modules to supply power to the thermochemical reaction, while the remaining wavelengths are fed into corresponding radiation absorbers to provide heat for the thermochemical reaction. The concentration ratio is ordered from low to high according to the different energy qualities of heat required for different steps in the subsequent magnesium-chlorine cycle: the first stage uses a medium concentration ratio of 495-505, and the second stage uses a high concentration ratio of 595-605. The area ratio of the two is approximately 5.5:4.5, based on the different amounts of heat and electricity required for different steps in the subsequent magnesium-chlorine cycle. A tower or dish-type concentrator design is selected depending on the scale.

[0035] In one specific embodiment, the method further includes the following steps: the hydrolysis reactor 8a uses the heat energy generated by the high-temperature radiation absorber 3b to drive the hydrolysis reaction, maintaining the temperature inside the reactor at 500~550℃; the chlorination reactor 8b uses the heat energy generated by the medium-high temperature radiation absorber 3a to heat the raw material Cl2 for the chlorination reaction, maintaining the temperature inside the reactor at 450~500℃; and the electrolysis reactor 8c uses the power generated by the photovoltaic cell module 4 to drive the electrolysis reaction.

[0036] In one specific embodiment, the method further includes the following steps: the solid MgO product of the hydrolysis reaction is supplied to the chlorination reactor 8b as a raw material for the chlorination reaction, and the HCl gas product is supplied to the electrolysis reactor 8c as a raw material for the electrolysis reaction; the solid MgCl2 product of the chlorination reaction is supplied to the hydrolysis reactor 8a as a raw material for the hydrolysis reaction, and the oxygen product leaves the cycle; the Cl2 product of the electrolysis reaction is supplied to the chlorination reactor 8b as a raw material for the chlorination reaction, and the hydrogen product leaves the cycle; the hydrogen produced by the electrolysis reaction is stored in the hydrogen storage tank 9; and the oxygen produced by the chlorination reaction is stored in the oxygen storage tank 10.

[0037] In one specific embodiment, the three-step magnesium-chlorine cycle requires 102.22 kJ / (mol H2) of thermal energy and 270.16 kJ / (mol H2) of electrical energy. An excess of preheated hot water is introduced to ensure the reaction proceeds fully. The first stage uses a medium-concentration photovoltaic (MCP) with a concentration ratio of 495-505, achieving a photo-thermal conversion efficiency of 92.37% and a photo-electric conversion efficiency of 67.74% through frequency division. The second stage uses a high-concentration photovoltaic (MCP) with a concentration ratio of 595-605, achieving a photo-thermal conversion efficiency of 92.72% and a photo-electric conversion efficiency of 75.57% through frequency division. The system's hydrogen production efficiency is 56.29%. It is evident that the system and method of this invention, based on the principle of energy quality matching, employs multi-stage frequency division to obtain electrical / thermal energy of different qualities, supplying it in stages to the thermochemical cycle for hydrogen production. This achieves complementary coupling of different energy qualities based on energy gradient conversion, providing a highly efficient solar hydrogen production pathway.

[0038] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A multi-stage concentrated light frequency division driven magnesium-chlorine cycle hydrogen production system, characterized in that, This includes a solar full-spectrum multi-stage concentrating and frequency-dividing utilization subsystem and a magnesium-chlorine cycle hydrogen production subsystem; The solar full-spectrum multi-stage concentrating and frequency-dividing utilization subsystem includes a two-stage solar spectrum concentrator, a frequency-dividing module, a radiation absorber, a photovoltaic power generation module, a battery, a thermal storage module, and a heat exchange module; the magnesium-chlorine cycle hydrogen production subsystem includes a magnesium-chlorine cycle hydrogen production reactor; The two-stage solar concentrator concentrates sunlight with two different concentration ratios. The concentrated beams with different concentration ratios are divided by two frequency-dividing components. The usable photovoltaic light energy after frequency division enters the photovoltaic power generation module to generate photovoltaic power, while the remaining light energy enters two radiation absorbers according to the concentration ratio and produces heat energy at different temperatures. The battery is used to store the electrical energy generated by the photovoltaic power generation module. The heat storage component uses its internal heat storage medium to store a portion of the heat generated by the radiation absorber. The heat exchanger component is used to perform heat exchange between different radiation absorbers and reactants in the magnesium-chlorine cycle hydrogen production subsystem. The magnesium-chlorine cycle hydrogen production reactor includes a hydrolysis reactor (8a) for hydrolysis reaction, a chlorination reactor (8b) for chlorination reaction, and an electrolysis reactor (8c) for electrolysis reaction. The magnesium-chlorine cycle hydrogen production reactor uses the electrical energy generated by the photovoltaic power generation module and the thermal energy at different temperatures generated by different radiation absorbers to carry out the magnesium-chlorine cycle reaction. Its net reaction is the decomposition of water into hydrogen and oxygen.

2. The multi-stage concentrated light frequency division driven magnesium-chlorine cycle hydrogen production system according to claim 1, characterized in that: The solar spectrum multi-stage concentrating module includes a first-stage medium-concentrating module (1a) and a second-stage high-concentrating module (1b). Among them, the first-stage medium-multiplexing photovoltaic module (1a) provides a concentration multiple of 495~505 times. The resulting concentrated beam enters the medium-multiplexing frequency divider module (2a) for spectral frequency division. The photovoltaic usable wavelength band light energy is used for photovoltaic power generation, and the remaining wavelength band light energy enters the medium-temperature radiation absorber (3a) to heat the chlorine gas, the raw material for the chlorination reaction in the magnesium-chlorine cycle hydrogen production reactor, and preheat the heat storage medium in the medium-temperature heat storage module (6a). The second-stage high-concentration module (1b) provides a concentration factor of 595~605 times. The resulting concentrated beam enters the high-concentration frequency division module (2b) for spectral frequency division. Part of the frequency-divided light energy is used for photovoltaic power generation, and the remaining light energy enters the high-temperature radiation absorber (3b) to heat the water to the temperature required for the hydrolysis reaction in the magnesium-chlorine cycle hydrogen production reactor and preheat the heat storage medium in the high-temperature heat storage module (6b). The storage battery is used to power the electrolysis reaction in the magnesium-chlorine cycle hydrogen production reactor; the photovoltaic power generation module has a photovoltaic cell waste heat utilization device (4b), which recovers the heat energy of the photovoltaic power generation module to preheat hot water as a raw material for thermochemical reactions.

3. The multi-stage concentrated light frequency division driven magnesium-chlorine cycle hydrogen production system according to claim 1, characterized in that: The thermal storage component stores a portion of the heat generated by the radiation absorber when there is sufficient solar energy input, and provides heat to the heat exchanger component when there is insufficient solar energy input to ensure stable operation of the system day and night.

4. The multi-stage concentrated light frequency division driven magnesium-chlorine cycle hydrogen production system according to claim 1, characterized in that: The hydrolysis reaction in the hydrolysis reactor (8a) requires a reaction temperature of 500~550℃. The chemical reaction equation is: MgCl2+H2O→MgO+2HCl. The product MgO is fed into the chlorination reactor (8b) as a raw material, and the product HCl is fed into the electrolysis reactor (8c) as a raw material. The chlorination reaction in the chlorination reactor (8b) requires a reaction temperature of 450~500℃. The chemical reaction equation is: MgO+Cl2→MgCl2+0.5O2. The product MgCl2 is fed into the hydrolysis reactor (8a) as a raw material. The product O2 is stored in the oxygen storage tank (10) after exothermic reaction. This step is an exothermic reaction. The electrolysis reaction in the electrolysis reactor (8c) requires a reaction temperature of 90°C. The chemical reaction equation is: 2HCl→H2+Cl2. The product Cl2 is fed into the chlorination reactor (8b) as a raw material. The product H2 is stored in the hydrogen storage tank (9) after exothermic reaction. The electrical energy required for this step is provided by the electrical energy stored in the battery.

5. The multi-stage concentrated light frequency division driven magnesium-chlorine cycle hydrogen production system according to claim 2, characterized in that: The heat exchanger assembly includes a medium-temperature molten salt heat exchanger (7a), a medium-high temperature molten salt heat exchanger (7b), a primary water heat exchanger (7c), a secondary water heat exchanger (7d), a tertiary water heat exchanger (7e), a magnesium compound heat exchanger (7f), a primary chlorine heat exchanger (7g), and a secondary chlorine heat exchanger (7h). Among them, the medium-temperature molten salt heat exchanger (7a) is used to input the heat from the medium-temperature heat storage component (6a) or the medium-temperature radiation absorber (3a) into the secondary chlorination heat exchanger (7h); the medium-high temperature molten salt heat exchanger (7b) is used to input the heat from the medium-high temperature heat storage component (6b) or the high temperature radiation absorber (3b) into the hydrolysis reactor (8a) to provide the energy required for the reaction and maintain the operating temperature; The primary water heat exchanger (7c) is used to cool the H2 produced by the electrolysis reactor (8c) and recover the heat to heat the water preheated by the photovoltaic cell waste heat utilization device (4b); the secondary water heat exchanger (7d) is used to cool the high-temperature HCl produced by the hydrolysis reactor (8a) and recover the heat to further heat the water; the tertiary water heat exchanger (7e) is used to further heat the water into steam using the heat released by the chlorination reaction. The magnesium compound heat exchanger (7f) is used to cool the high-temperature MgO produced by the hydrolysis reactor (8a) and recover the heat to heat the MgCl2 produced by the chlorination reactor (8b); The primary chlorine heat exchanger (7g) is used to cool the O2 produced by the chlorination reactor (8b) and recover the heat to heat the Cl2 produced by the electrolysis reactor (8c); the secondary chlorine heat exchanger (7h) is used to further heat the Cl2 using the heat from the medium-temperature molten salt heat exchanger (7a) to bring it to the temperature required for the chlorination reaction.

6. The multi-stage concentrated light frequency division driven magnesium-chlorine cycle hydrogen production system as described in claim 4, characterized in that: The system also includes a solid-liquid material transport system, which transports the solid MgO and HCl gas generated in the hydrolysis reactor (8a) into the chlorination reactor (8b) and the electrolysis reactor (8c), respectively, transports the solid MgCl2 generated in the chlorination reactor (8b) into the hydrolysis reactor (8a), and transports the Cl2 generated in the electrolysis reactor (8c) into the chlorination reactor (8b).

7. The multi-stage concentrated light frequency division driven magnesium-chlorine cycle hydrogen production system according to claim 2, characterized in that: The frequency divider is a spectrally selective filter, including a medium-concentration frequency divider (2a) and a high-concentration frequency divider (2b). It is an optical interference multilayer frequency divider film formed by alternating deposition of TiO2 and SiO2 materials on a transparent substrate, which is used to achieve selective transmission of solar spectrum. The medium-concentration frequency divider (2a) transmits the wavelength band of 390nm~670nm to the photovoltaic power generation module below for power generation, and the remaining wavelength band enters the medium-temperature radiation absorber (3a) to be converted into heat energy. The high-concentration frequency divider (2b) transmits the wavelength band of 480nm~630nm to the photovoltaic power generation module below for power generation, and the remaining wavelength band enters the high-temperature radiation absorber (3b) to be converted into heat energy.

8. The multi-stage concentrated light frequency division driven magnesium-chlorine cycle hydrogen production system according to claim 2, characterized in that: Radiation absorbers are used to absorb focused sunlight and convert it into heat energy. They include a medium-temperature radiation absorber (3a) and a medium-high temperature radiation absorber (3b). The medium-temperature radiation absorber (3a) provides heat energy of 490~510℃, and the medium-high temperature radiation absorber (3b) provides heat energy of 540~560℃.

9. The multi-stage concentrated light frequency division driven magnesium-chlorine cycle hydrogen production system according to claim 2, characterized in that: The thermal storage components include a medium-temperature thermal storage component (6a) and a medium-high temperature thermal storage component (6b). The medium-temperature thermal storage component (6a) operates at a temperature of 500°C, and the medium-high temperature thermal storage component (6b) operates at a temperature of 550°C. Both adopt molten salt thermal storage. The heat transfer medium between the radiation absorber, the thermal storage components and the heat exchange components is a heat transfer fluid.

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