Photovoltaic and thermochemical coupled full-spectrum solar hydrogen production system

Abstract

The invention discloses a photovoltaic and thermochemical coupled full-spectrum solar hydrogen production system. The system comprises a concentrating and frequency dividing subsystem, a photovoltaic electrolysis subsystem and a photo-thermal methanol reforming subsystem, the light condensation and frequency division subsystem is used for carrying out focusing and frequency division on the incident full-spectrum sunlight, and then the full-spectrum sunlight enters the photovoltaic electrolysis subsystem and the photo-thermal methanol reforming subsystem; the waveband sunlight matched with the photovoltaic band gap is focused and incident into the photovoltaic electrolysis subsystem to be converted into electric energy, and then water electrolysis for hydrogen production is driven; and the sunlight of the rest wave band is focused and incident to the photo-thermal methanol cracking subsystem to be converted into heat energy, so that the methanol / water reaction solution is driven to perform methanol reforming thermal chemical reaction for hydrogen production. And the photovoltaic electrolysis subsystem is connected with the photo-thermal methanol reforming subsystem, and is used for recycling waste heat generated in the photovoltaic power generation process for preheating a reaction solution and cooling a photovoltaic device at the same time. According to the invention, efficient conversion from full-spectrum solar energy to hydrogen energy is realized.

Description

Technical Field

[0001] The embodiments of the present disclosure belong to the field of solar energy technology, and specifically relate to a full-spectrum solar hydrogen production system that couples photovoltaics and thermochemicals. Background Art

[0002] Under the strategic goal of "carbon peak and carbon neutrality", the development of solar energy utilization will promote the low-carbonization of the energy structure. Solar hydrogen production can store volatile solar energy in hydrogen chemical energy, which is one of the ways to achieve large-scale utilization of solar energy. The full spectrum of solar energy can be divided into ultraviolet light (290-400nm), visible light (400-760nm) and infrared light (760-5300nm). The photon energy gradually decreases in the order of ultraviolet, visible and infrared light. Exploring the conversion method of the full spectrum of solar energy to hydrogen is the key to improving the efficiency of solar hydrogen production.

[0003] Photovoltaic electrolysis of water to produce hydrogen is currently the most widely used solar hydrogen production technology. Limited by the band gap energy of semiconductor materials, the photovoltaic photoelectric conversion process is selective to the solar spectrum and can only use visible and part of infrared light. Therefore, the efficiency of photovoltaic power generation is currently low, which also limits the efficiency of photovoltaic electrolysis of water to produce hydrogen. Methanol is an energy carrier that is easy to store and transport and economical. Using methanol reforming reaction to produce hydrogen will be a way to produce hydrogen. Solar thermal conversion provides heat absorbed by the methanol reforming hydrogen production process, and can also store solar energy in hydrogen chemical energy. However, in this technology, ultraviolet and visible light with higher photon energy are converted into medium and low temperature heat, and then drive the methanol reforming reaction. The working capacity of short-wave photons is not fully utilized, resulting in the loss of short-wave photons' working capacity.

[0004] Therefore, how to achieve efficient conversion of the full spectrum of solar energy into hydrogen is a technical problem that needs to be urgently solved in the field of solar hydrogen production. Summary of the invention

[0005] The embodiments of the present disclosure aim to solve at least one of the technical problems existing in the prior art and provide a full-spectrum solar hydrogen production system that couples photovoltaics and thermochemicals.

[0006] In one aspect of the embodiments of the present disclosure, a full-spectrum solar hydrogen production system coupling photovoltaic and thermochemical is provided.

[0007] Among them, the focusing and frequency division subsystem focuses and divides the incident full-spectrum sunlight, and then makes it incident on the photovoltaic electrolysis subsystem and the photothermal methanol reforming subsystem; the focusing and frequency division subsystem focuses the sunlight of the band matching the photovoltaic band gap into the photovoltaic electrolysis subsystem to convert it into electrical energy, thereby driving the electrolysis of water to produce hydrogen; the focusing and frequency division subsystem focuses the sunlight of the remaining bands into the photothermal methanol cracking subsystem to convert it into thermal energy, thereby driving the methanol / water reaction solution to carry out methanol reforming thermochemical reaction to produce hydrogen; the photovoltaic electrolysis subsystem is connected to the photothermal methanol reforming subsystem, and the photothermal methanol reforming subsystem recovers the waste heat generated in the photovoltaic power generation process for preheating the methanol / water reaction solution and cooling the photovoltaic.

[0008] Optionally, the light-collecting and frequency-splitting subsystem comprises a trough-type condenser and a frequency-splitting condenser; the trough-type condenser is used to collect incident full-spectrum sunlight;

[0009] The frequency-splitting concentrator is used to reflect the sunlight of the wavelength band matching the photovoltaic band gap of the photovoltaic electrolysis subsystem in the full-spectrum sunlight to the photovoltaic power generation module of the photovoltaic electrolysis subsystem, and the frequency-splitting concentrator transmits the sunlight of the remaining wavelength bands to the photothermal methanol reforming module of the photothermal methanol reforming subsystem for conversion into thermal energy;

[0010] Optionally, the photovoltaic-electrolysis subsystem includes a photovoltaic power generation module, a maximum power tracking device, a DC / DC converter and an electrolytic cell connected in sequence.

[0011] Optionally, the photovoltaic power generation module includes a photovoltaic component and a photovoltaic fixing plate; the photovoltaic component is arranged on the surface of the photovoltaic fixing plate; a fluid channel is arranged in the photovoltaic fixing plate;

[0012] The photovoltaic module is used to convert incident sunlight of a wavelength matching its photovoltaic band gap into electrical energy; the photovoltaic fixing plate is used to fix the photovoltaic module and transfer the waste heat generated in the process of converting the photovoltaic module into electrical energy to the internal fluid channel for preheating the methanol / water reaction solution of the thermochemical reaction and cooling the photovoltaic module.

[0013] Optionally, the photothermal methanol reforming subsystem includes a photothermal methanol reforming module, a methanol tank, a water tank, a methanol pump, a water pump, a mixed solution pump, a methanol flow meter, a flow valve, a water flow meter, a mixed solution flow meter, a No. 1 heat exchanger, a water vapor shift reactor, a No. 2 heat exchanger, a condenser, a gas-liquid separator, a carbon dioxide pressure swing adsorption device, a carbon dioxide storage tank and a gas storage tank;

[0014] The methanol tank, methanol pump and methanol flowmeter are connected in sequence through a methanol pipeline; the water tank, water pump and water flowmeter are connected in sequence through a water pipeline, and are diverted through a No. 1 water valve, so that part of the water in the water pipeline merges with the methanol in the methanol pipeline to form a methanol / water reaction solution that enters the methanol / water pipeline; and the other part of the water flows into the downstream water pipeline;

[0015] The inlet end of the fluid channel in the photovoltaic power generation module is connected to the methanol / water pipeline and the water pipeline respectively; the output end of the fluid channel is connected to the inlet end of the thermochemical reaction tube in the photothermal methanol reforming module through the liquid inlet pipeline, and is also connected to the electrolyzer through the water pipeline;

[0016] The input end of the photothermal methanol reforming module is connected to the No. 1 heat exchanger, the No. 2 heat exchanger and the output end of the photovoltaic power generation module in sequence through a liquid inlet pipeline; the output end of the photothermal methanol reforming module is connected to the No. 1 heat exchanger, the water vapor shift reactor, the No. 2 heat exchanger, the condenser, the gas-liquid separator, the carbon dioxide pressure swing adsorption device and the gas storage tank in sequence through a liquid outlet pipeline.

[0017] Optionally, the photothermal methanol reforming module comprises a vacuum tube, a thermochemical reaction tube and a catalyst bed; the thermochemical reaction tube is arranged in the vacuum tube; the catalyst bed is arranged in the thermochemical reaction tube;

[0018] The vacuum tube is used to transmit sunlight and to maintain a vacuum environment between the vacuum tube and the thermochemical reaction tube to reduce internal heat loss;

[0019] The thermochemical reaction tube is used to absorb incident sunlight and convert it into thermal energy, and transfer the heat to the catalyst bed;

[0020] The catalyst bed is used to catalyze the methanol / water reaction solution to carry out a methanol reforming reaction.

[0021] Optionally, the lower cutoff wavelength of the selective reflection band of the frequency-division condenser is 500 nm; the upper cutoff wavelength of the selective reflection band of the frequency-division condenser is the photon wavelength corresponding to the photovoltaic band gap energy.

[0022] Optionally, the trough concentrator and the frequency-splitting concentrator both have a parabolic structure; the photovoltaic power generation module is arranged in the middle position of the trough concentrator; the photothermal methanol reforming module is arranged at the focal position of the trough concentrator; the frequency-splitting concentrator is arranged between the photovoltaic power generation module and the photothermal methanol reforming module, and is used to reflect part of the band of sunlight reflected from the trough concentrator to the photovoltaic power generation module again, and transmit the remaining band of sunlight to the photothermal methanol reforming module.

[0023] Optionally, the total width of the trough condenser is L1, the total width of the frequency-dividing condenser is L2, and the width of the photovoltaic power generation module is L PV , the outer diameter of the photothermal methanol reforming module is D1;

[0024] The energy of photons of different wavelengths incident on the photovoltaic power generation module is expressed as:

[0025] I PV (λ)=I PV,1 (λ)+I PV,2 (λ)+I PV,3 (λ);

[0026] The energy of photons of different wavelengths incident on the photothermal methanol reforming module is expressed as:

[0027] I TR (λ)=I TR,4 (λ)+I TR,5 (λ)+I TR,6 (λ)+I TR,7 (λ);

[0028] Where λ is the wavelength, and the reflectivity of the trough condenser for photons of different wavelengths is ρ pc ; The reflectivity of the frequency-dividing condenser for photons of different wavelengths is ρ sbs , the transmittance is τ sbs ; The absorption rate of the photovoltaic power generation module for the incident light is α PV ; The absorption rate of the incident light by the photothermal methanol reforming module is α TR ; At different wavelengths, the incident power is I in (λ) condition, the photon energy of different wavelengths absorbed by the photovoltaic power generation module is expressed as:

[0029] I PV (λ)=(L1ρ pc ρ sbs (λ)+(L PV -D1)τ sbs (λ)+L2τ sbs (λ)ρ pc ρ sbs (λ))I in (λ)α PV ;

[0030] The energy of photons of different wavelengths absorbed by the CTM reforming module is expressed as:

[0031] I TR (λ)=(L1ρ pc τ sbs (λ)+L2ρ sbs (λ)+(L PV-D1)ρ sbs (λ)+L2τ sbs (λ)ρ pc τ sbs (λ)+D1)I in (λ)α TR ;

[0032] Among them, based on the above conditional formula, the energy of photons of different bands absorbed by the photovoltaic power generation module and the photothermal methanol reforming module can be obtained to calculate the electric energy generated by the photovoltaic power generation module and the heat provided for the methanol reforming reaction of the photothermal methanol reforming module.

[0033] Optionally, the photovoltaic module can be manufactured by a dicing process, and the dicing structures are connected in series to form the photovoltaic module; the material of the photovoltaic fixing plate includes copper or aluminum.

[0034] The beneficial effects of the embodiments of the present disclosure include:

[0035] In the present disclosure, the focusing and frequency division subsystem divides the wavelength band of full-spectrum sunlight into two parts, including the wavelength band of sunlight that matches the photovoltaic band gap of the photovoltaic electrolysis subsystem, and other wavelength bands of sunlight. Among them, the wavelength band sunlight that matches the photovoltaic band gap energy is incident on the photovoltaic electrolysis subsystem to generate electricity for electrolysis to produce hydrogen. The sunlight of other wavelength bands is incident on the photothermal methanol reforming subsystem and converted into thermal energy to drive the methanol / water reaction solution to carry out reforming reaction to produce hydrogen. Therefore, the system disclosed in the present disclosure realizes the efficient conversion of full-spectrum solar energy to hydrogen energy. Compared with single photovoltaic electrolysis to produce hydrogen, the unabsorbed loss of long-wave photons and the extra kinetic energy loss of short-wave photons in the photovoltaic power generation process are greatly reduced; compared with single photothermal methanol reforming to produce hydrogen, the working capacity of short-wave photons is fully utilized, and after being converted into electrical energy, it directly drives water decomposition to produce hydrogen, reducing the consumption of methanol chemical fuel. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic structural diagram of a photovoltaic and thermochemical coupled full-spectrum solar hydrogen production system according to the present invention;

[0037] Figure 2 It is a schematic diagram of the sunlight focusing and frequency division process of the present invention;

[0038] Figure 3 This is a schematic diagram of the structure of a photovoltaic power generation module according to the present invention;

[0039] Figure 4 This is a schematic diagram of the structure of a photothermal methanol reforming module described in the present invention.

[0040] In the figure, 1. trough condenser; 2. frequency-dividing condenser; 3. photovoltaic power generation module; 4. photothermal methanol reforming module; 5. maximum power tracking device; 6. DC / DC converter; 7. electrolyzer; 8. hydrogen tank; 9. first hydrogen valve; 10. methanol tank; 11. water tank; 12. methanol pump; 13. mixed solution pump; 14. water pump; 15. methanol flowmeter; 16. mixed solution flowmeter; 17. water flowmeter; 18. No. 1 water valve; 19. No. 1 mixed solution valve; 20. No. 2 water valve; 21. No. 2 mixed solution valve; 22. No. 1 heat exchanger; 23. water vapor shift reactor; 24. No. 2 heat exchanger; 25. condenser; 26. gas-liquid separator; 27. carbon dioxide pressure swing adsorption device; 28. carbon dioxide storage tank; 29. ​​second hydrogen valve; 30. gas storage tank. DETAILED DESCRIPTION

[0041] In order to enable those skilled in the art to better understand the technical solution of the present disclosure, the present disclosure is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0042] The following is a further detailed description of the implementation methods of the present application in conjunction with the accompanying drawings and examples. The detailed descriptions and drawings of the following examples are used to illustrate the principles of the present application, but cannot be used to limit the scope of the present application, that is, the present application is not limited to the described embodiments. In the description of the present application, it should be noted that, unless otherwise specified, the meaning of "multiple" is more than two; the orientation or position relationship indicated by the terms "upper", "lower", "left", "right", "inside", "outside", etc. is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. "Vertical" is not vertical in the strict sense, but within the error tolerance range. "Parallel" is not parallel in the strict sense, but within the error tolerance range.

[0043] In the description of this application, it should also be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0044] like Figure 1As shown, a photovoltaic and thermochemical coupled full-spectrum solar hydrogen production system includes a light-concentrating and frequency-splitting subsystem, a photovoltaic electrolysis subsystem, and a photothermal methanol reforming subsystem. The light-concentrating and frequency-splitting subsystem is used to focus and frequency-splitting incident full-spectrum sunlight.

[0045] Among them, the focusing and frequency division subsystem focuses and divides the incident full-spectrum sunlight, and then injects it into the photovoltaic electrolysis subsystem and the photothermal methanol reforming subsystem. The focusing and frequency division subsystem focuses the sunlight in the band that matches the photovoltaic band gap and injects it into the photovoltaic electrolysis subsystem to convert it into electrical energy, thereby driving the electrolysis of water to produce hydrogen. The focusing and frequency division subsystem focuses the sunlight in the remaining bands and injects it into the photothermal methanol cracking subsystem to convert it into thermal energy, thereby driving the methanol / water reaction solution to undergo a thermochemical reaction of methanol reforming to produce hydrogen. The photovoltaic electrolysis subsystem is connected to the photothermal methanol reforming subsystem, which recycles the waste heat generated in the photovoltaic power generation process for preheating the methanol / water reaction solution and cooling the photovoltaic.

[0046] In the present disclosure, the focusing and frequency division subsystem divides the wavelength band of full-spectrum sunlight into two parts, including the wavelength band of sunlight that matches the photovoltaic band gap of the photovoltaic electrolysis subsystem, and other wavelength bands of sunlight. Among them, the wavelength band sunlight that matches the photovoltaic band gap energy is incident on the photovoltaic electrolysis subsystem to generate electricity for electrolysis to produce hydrogen. The sunlight of other wavelength bands is incident on the photothermal methanol reforming subsystem and converted into thermal energy to drive the methanol / water reaction solution to carry out reforming reaction to produce hydrogen. Therefore, the system disclosed in the present disclosure realizes the efficient conversion of full-spectrum solar energy to hydrogen energy. Compared with single photovoltaic electrolysis to produce hydrogen, the unabsorbed loss of long-wave photons and the extra kinetic energy loss of short-wave photons in the photovoltaic power generation process are greatly reduced; compared with single photothermal methanol reforming to produce hydrogen, the working capacity of short-wave photons is fully utilized, and after being converted into electrical energy, it directly drives water decomposition to produce hydrogen, reducing the consumption of methanol chemical fuel.

[0047] In some embodiments, the focusing and frequency-splitting subsystem includes a trough-type concentrator 1 and a frequency-splitting concentrator 2, wherein the frequency-splitting concentrator 2 is disposed above the trough-type concentrator 1, and the trough-type concentrator 1 is used to converge incident full-spectrum sunlight. Full-spectrum sunlight includes ultraviolet light, visible light, and infrared light. The frequency-splitting concentrator 2 is used to reflect the wavelength band sunlight in the full-spectrum sunlight that matches the photovoltaic band gap of the photovoltaic electrolysis subsystem to the photovoltaic power generation module of the photovoltaic electrolysis subsystem, and the remaining wavelength band sunlight transmitted by the frequency-splitting concentrator is incident on the photothermal methanol reforming module of the photothermal methanol reforming subsystem, and is further converted into thermal energy.

[0048] In some embodiments, the photovoltaic electrolysis subsystem includes a photovoltaic power generation module 3, a maximum power tracking device 5, a DC / DC converter 6, and an electrolyzer 7. The photovoltaic power generation module 3 is connected to the maximum power tracking device 5, the maximum power tracking device 5 is connected to the DC / DC converter 6, and the DC / DC converter 6 is connected to the electrolyzer 7.

[0049] The photovoltaic power generation module 3 is used to convert the sunlight of a wavelength matching the photovoltaic band gap reflected by the frequency-dividing concentrator 2 into electrical energy, and to recover the waste heat generated in the process of converting into electrical energy.

[0050] The maximum power tracking device 5 is used to obtain the maximum power output of the photovoltaic power generation module 3 under different operating conditions.

[0051] The DC / DC converter 6 is used to adjust the output voltage to match the voltage required by the electrolysis cell 7 for electrolysis.

[0052] The electrolyzer 7 is used to consume the electric energy of the photovoltaic power generation module 3 to produce hydrogen. In some embodiments, the photovoltaic electrolysis subsystem includes a hydrogen tank 8 for storing the hydrogen produced by the electrolyzer 7. A first hydrogen valve 9 is provided on the pipeline between the electrolyzer 7 and the hydrogen tank 8.

[0053] In some embodiments, reference Figure 3 The photovoltaic power generation module 3 includes a photovoltaic component 3-1 and a photovoltaic fixing plate 3-2. The photovoltaic component 3-1 is arranged on the surface of the photovoltaic fixing plate 3-2, and a fluid channel is arranged in the photovoltaic fixing plate 3-2.

[0054] The photovoltaic module 3-1 is used to convert incident sunlight of a wavelength matching its photovoltaic band gap into electrical energy. The photovoltaic fixing plate 3-2 is used to fix the photovoltaic module 3-1 and transfer the waste heat generated in the process of converting the photovoltaic module 3-1 into electrical energy to the internal fluid channel for preheating the methanol / water reaction solution required for the thermochemical reaction.

[0055] Specifically, the photovoltaic module 3-1 is embedded in the upper surface of the photovoltaic fixed plate 3-2. The photovoltaic fixed plate 3-2 is provided with fluid channels 3-3, 3-4 and 3-5. Among them, the inlet end of one channel is connected to a single water pipeline, and the corresponding outlet end is connected to the electrolytic cell 7; the inlet ends of the other two channels are connected to the methanol / water pipeline, and the corresponding outlet ends are connected to the second heat exchanger 24.

[0056] In some embodiments, the photothermal methanol reforming subsystem includes a photothermal methanol reforming module 4, a methanol tank 10, a water tank 11, a methanol pump 12, a mixed solution pump 13, a water pump 14, a methanol flowmeter 15, a mixed solution flowmeter 16, a water flowmeter 17, a first water valve 18, a first mixed solution valve 19, a second water valve 20, a second mixed solution valve 21, a first heat exchanger 22, a water vapor shift reactor 23, a second heat exchanger 24, a condenser 25, a gas-liquid separator 26, a carbon dioxide pressure swing adsorption device 27, a carbon dioxide storage tank 28, a second hydrogen valve 29 and a gas storage tank 30. The photothermal methanol reforming module 4 is used to absorb the band solar energy transmitted by the frequency division concentrator and convert it into heat energy to drive the methanol / water reaction solution to perform a methanol reforming reaction. The gas storage tank 30 is used to store hydrogen.

[0057] The methanol tank 10, the methanol pump 12 and the methanol flowmeter 15 are connected in sequence through the methanol pipeline. The water tank 11, the water pump 14 and the water flowmeter 17 are connected in sequence through the water pipeline. The water pipeline is diverted through the No. 1 water valve 18 and connected to the methanol / water pipeline, so that part of the water in the water pipeline merges with the methanol in the methanol pipeline to form a methanol / water reaction solution that enters the methanol / water pipeline, wherein the methanol / water reaction solution is conducted to the liquid inlet pipeline through the fluid channel. The diversion of the No. 1 water valve allows another part of the water in the water pipeline to be connected to the fluid channel through the water pipeline, and then conducted to the electrolyzer by the fluid channel.

[0058] The methanol tank 10 and the water tank 11 are used to store the methanol and aqueous solution required for the methanol reforming reaction, respectively. The methanol pump 12 and the water pump 14 are used to drive the flow of the methanol and aqueous solution, respectively. The methanol flowmeter 15 and the water flowmeter 17 are used to control the flow of the methanol and aqueous solution according to different working conditions to modulate the molar ratio of methanol to water in the methanol / water reaction solution. The inlet ends of the fluid channel in the photovoltaic power generation module are connected to the methanol / water pipeline and the water pipeline, respectively, wherein the liquid side of the gas-liquid separator is connected to the methanol / water pipeline through a pipeline, and a mixed solution pump 13 and a mixed solution flowmeter 16 are provided on the pipeline. The gas-liquid separator is used to recover the methanol / water reaction solution that has not reacted completely and pass it into the methanol / water pipeline again.

[0059] Furthermore, the inlet end of the fluid channel of the photovoltaic power generation module 3 is connected to the methanol / water pipeline and the water pipeline respectively, and the output end of the fluid channel of the photovoltaic power generation module 3 is connected to the inlet end of the thermochemical reaction tube in the photothermal methanol reforming module 4 through the liquid inlet pipeline, and is also connected to the electrolytic cell through the water pipeline.

[0060] The input end of the photothermal methanol reforming module 4 is connected to the No. 1 heat exchanger 22, the No. 2 heat exchanger 24 and the output end of the photovoltaic power generation module 3 in sequence through a liquid inlet pipeline, and the output end of the photothermal methanol reforming module 4 is connected to the No. 1 heat exchanger 22, the water vapor shift reactor 23, the No. 2 heat exchanger 24, the condenser 25, the gas-liquid separator 26, the carbon dioxide pressure swing adsorption device 27 and the gas storage tank 30 in sequence through a liquid outlet pipeline.

[0061] Specifically, the No. 1 heat exchanger 22 is used to recover the sensible heat of the mixed gas generated by the reaction and the incompletely reacted methanol vapor and water vapor, and is used to preheat the methanol / water mixed solution flowing into the photothermal methanol reforming module 4 .

[0062] The water gas shift reactor 23 is used to drive the carbon monoxide produced by the side reaction in the mixed gas to further react with water to generate carbon dioxide and hydrogen, thereby increasing the proportion of H2 in the synthesis gas. The reaction formula for the reaction of carbon monoxide and water to generate carbon dioxide and hydrogen is:

[0063] CO+H2O=CO2+H2

[0064] The second heat exchanger 24 is used to further deeply recover the heat in the mixed gas and the incompletely reacted reactants, and is used to preheat the methanol / water mixed solution flowing into the photothermal methanol reforming module 4.

[0065] The condenser 22 is used to condense the incompletely reacted methanol vapor and water vapor in the reaction product into liquid form. Further, the gas-liquid separator 26 is used to perform gas-liquid separation to obtain a methanol / water reaction solution and a mixed gas produced by the reaction, wherein the separated methanol / water reaction solution is introduced into the methanol / water pipeline through a pipeline.

[0066] The carbon dioxide pressure swing adsorption device 27 is used to adsorb carbon dioxide in the mixed gas to obtain hydrogen with higher purity and store it in the hydrogen tank 8 , and the desorbed carbon dioxide is stored in the carbon dioxide storage tank 28 .

[0067] In some embodiments, a first water valve 18 and a second water valve 20 are provided on the water pipeline, and the second water valve 20 is located downstream of the first water valve 18 and is used for water flow control. A first mixed solution valve 19 and a second mixed solution valve 21 are provided on the methanol / water pipeline and are used for flow control of the mixed methanol / water reaction solution.

[0068] In some embodiments, reference Figure 4 The photothermal methanol reforming module 4 includes a vacuum tube 4-1, a thermochemical reaction tube 4-2 and a catalyst bed 4-3. The thermochemical reaction tube 4-2 is arranged in the vacuum tube 4-1, and the catalyst bed 4-3 is arranged in the thermochemical reaction tube 4-2.

[0069] The vacuum tube 4-1 is used to transmit sunlight in a band other than that matching the photovoltaic band gap of the photovoltaic electrolysis subsystem 3, and maintain a vacuum environment between the thermochemical reaction tube 4-2. The thermochemical reaction tube 4-2 is used to absorb incident sunlight and convert it into thermal energy, and transfer the heat to the catalyst bed 4-3. The catalyst bed 4-3 is used to catalyze the methanol / water reaction solution to perform a methanol reforming reaction.

[0070] In some embodiments, the vacuum tube 4 - 1 is a quartz glass tube.

[0071] In some embodiments, the thermochemical reaction tube is made of stainless steel with a highly absorbent coating on the surface.

[0072] The working principle of the focusing and frequency division subsystem, refer to Figure 2 There are three main types of light incident on the photovoltaic power generation module 3 after passing through the focusing and frequency division subsystem, including:

[0073] 1. The light is reflected and focused by the slotted condenser 1 and further reflected and converged by the frequency-dividing condenser 2①.

[0074] 2. Light directly incident through the frequency division condenser 2②.

[0075] 3. The light is transmitted through the frequency-dividing condenser 2, further reflected and focused by the slot condenser 1, and further reflected and focused by the frequency-dividing condenser 2③.

[0076] There are four main types of light that enter the photothermal methanol reforming module 4 after passing through the focusing and frequency division subsystem, including:

[0077] 1. Light reflected by the slot condenser 1 and further transmitted by the frequency-dividing condenser 2④.

[0078] 2. Directly incident on the frequency division condenser 2 and reflected again to converge the light⑤.

[0079] 3. The light ⑥ is transmitted through the frequency division condenser 2, further reflected by the slot condenser 1, and further transmitted through the frequency division condenser 2.

[0080] 4. Light directly incident on the photothermal methanol reforming module 4⑦.

[0081] The four main losses of photovoltaics include long-wave photon non-absorption loss, short-wave photon extra kinetic energy loss, compound loss and isothermal dissipation loss. The disclosed system adopts frequency division technology to divide the spectrum into bands, and the band solar energy that matches the photovoltaic band gap energy is incident on the photovoltaic power generation module 3, and the other band solar energy is focused on the photothermal methanol reforming module 4, thereby realizing the effective utilization of the full spectrum of solar energy. Compared with the traditional single photovoltaic that only uses visible and part of the infrared light band for power generation, the disclosure greatly reduces the long-wave photon non-absorption loss and the short-wave photon extra kinetic energy loss. Furthermore, the methanol / water mixed solution and water can recycle the remaining heat loss of photovoltaics through the fluid channel in the photovoltaic fixed plate 3-2 for heating the reaction solution and water for electrolysis.

[0082] In a specific example provided by the present disclosure, the water in the water tank 11 is divided through the No. 1 water valve 18 on the water pipeline, a part of the water enters the fluid channel 3-5 through the pipeline provided with the No. 1 water valve 18 and flows to the electrolytic cell 7 for electrolysis, and the other part of the water flows into the methanol / water pipeline provided with the No. 1 mixed solution valve 19. It can be understood that the specific distribution of the fluid channel 3-3, the fluid channel 3-4 and the fluid channel 3-5 can be set as needed, including but not limited to the above-mentioned setting method.

[0083] Photovoltaic cells have a negative temperature effect, that is, the higher the temperature, the lower the power generation efficiency. In some embodiments, the methanol / water mixed solution and electrolysis water disclosed in the present invention can cool the photovoltaic fixed plate 3-2 through the fluid channel, which can suppress the negative temperature effect of the photovoltaic power generation module 3.

[0084] The lower cutoff wavelength of the selective transmission band of the frequency-dividing condenser 2 is 500 nm, and the upper cutoff wavelength of the selective transmission band of the frequency-dividing condenser 2 is the photon wavelength corresponding to the photovoltaic band gap energy.

[0085] Photovoltaic module 3-1 can use different types of photovoltaics such as monocrystalline silicon, polycrystalline silicon, gallium arsenide, cadmium telluride, copper indium gallium selenide, etc. Different types of photovoltaic band gap energies are different, so the solar light bands that match their band gap energies are different. Here, the lower cutoff wavelength of the selective reflection band of the frequency-dividing concentrator 2 is uniformly 500nm, mainly because the external quantum efficiency of short-wave photon power generation is low, and the additional kinetic energy loss of short-wave photons is large, which will produce large heat losses. The upper cutoff wavelength is the photon wavelength corresponding to the photovoltaic band gap energy. Therefore, the selective reflection wavelength of the frequency-dividing concentrator 2 can be set as shown in Table 1 according to the different types of photovoltaics selected.

[0086]

[0087] Table 1

[0088] Referring to Table 1, the material of the frequency-dividing condenser 2 is single crystal silicon, for example, the lower cutoff wavelength is 500nm, and the upper cutoff wavelength is 1080nm. Therefore, the frequency-dividing condenser 2 can reflect the light in the 500-1080nm band to the photovoltaic power generation module 3 for power generation, and transmit the light in the wavelength band below 500nm and above 1080nm to the photothermal methanol reforming module 4, which is converted into heat energy for methanol reforming reaction, thus realizing the efficient conversion of full-spectrum sunlight.

[0089] The trough condenser and the frequency-dividing condenser are both parabolic structures. The photovoltaic power generation module is set in the middle of the trough condenser, and the photothermal methanol reforming module is set at the focus position of the trough condenser. Specifically, a multi-objective optimization method is adopted to optimize the relative position of the frequency-dividing condenser, so that the energy flow distribution on the photovoltaic surface is more uniform while ensuring the focusing efficiency.

[0090] In some embodiments, the total width of the trough concentrator is L1, the total width of the frequency-dividing concentrator is L2, and the width of the photovoltaic power generation module is L PV The outer diameter of the photothermal methanol reforming module is D1.

[0091] The energy of photons of different wavelengths incident on the photovoltaic power generation module is expressed as:

[0092] I PV (λ)=I PV,1 (λ)+I PV,2 (λ)+I PV,3 (λ);

[0093] The energy of photons of different wavelengths incident on the photothermal methanol reforming module is expressed as:

[0094] I TR (λ)=I TR,4 (λ)+I TR,5 (λ)+I TR,6 (λ)+I TR,7 (λ);

[0095] Among them, λ is the wavelength, I represents energy, and the reflectivity of the trough condenser for photons of different wavelengths is ρ pc The reflectivity of the frequency-dividing condenser for photons of different wavelengths is ρ sbs , the transmittance is τ sbs The absorption rate of the photovoltaic power generation module for the incident light is α PV The absorption rate of the incident light by the photothermal methanol reforming module is α TR , at different wavelengths the incident power is I in (λ) condition, the energy of photons of different wavelengths absorbed by the photovoltaic power generation module side is expressed as:

[0096] I PV (λ)=(L1ρpc ρ sbs (λ)+(L PV -D1)τ sbs (λ)+L2τ sbs (λ)ρ pc ρ sbs (λ))I in (λ)α PV .

[0097] The energy of photons of different wavelengths absorbed by the CTM reforming module is expressed as:

[0098] I TR (λ)=(L1ρ pc τ sbs (λ)+L2ρ sbs (λ)+(L PV -D1)ρ sbs (λ)+L2τ sbs (λ)ρ pc τ sbs (λ)+D1)I in (λ)α TR .

[0099] Among them, based on the above conditional formula, the energy of photons of different wavelengths absorbed by the photovoltaic power generation module 3 and the photothermal methanol reforming module 4 can be obtained to calculate the electric energy generated by the photovoltaic power generation module 3 and the heat provided for the methanol reforming reaction of the photothermal methanol reforming module 4. Among them, the methanol in the methanol tank 10 and the water in the water tank are merged into the methanol / water pipeline. The methanol / water solution from the liquid side of the gas-liquid separator is also merged into the methanol / water pipeline, and enters the fluid channel 3-3 and the fluid channel 3-4 through the No. 1 mixed solution valve 19 and the No. 2 mixed solution valve 21 on the methanol / water pipeline, and flows to the photothermal methanol reforming module 4.

[0100] The electrolytic cell 7 is an alkaline electrolytic cell. In other embodiments, the electrolytic cell 7 is a proton exchange membrane electrolytic cell. The water used for electrolysis in the electrolytic cell 7 is connected to the photovoltaic fixed panel 3-2 through a pipeline by a water pipe, and the water for electrolysis flows into the electrolytic cell 7 through a fluid channel. The water for electrolysis recovers the waste heat generated by the photovoltaic power generation module 3 during power generation in the fluid channel, thereby improving the electrolysis efficiency. In a specific example, the electrolyzed water can be heated to 60-90°C, which significantly improves the electrolysis efficiency.

[0101] The main reactions occurring in the photothermal methanol reforming module 4 are:

[0102] CH3OH+H2O=CO2+3H2,

[0103] There are also two side effects:

[0104] CH3OH=CO+2H2,

[0105] CO+H2O=CO2+H2.

[0106] The water vapor shift reactor 23 is a fixed bed reactor for the water vapor shift reaction. In some embodiments, the water vapor shift reactor 23 uses an iron-based, copper-based or cobalt-molybdenum-based catalyst to accelerate the reaction, wherein the reaction temperature is in the range of 180-250°C, so it is necessary to preliminarily cool the methanol reforming reaction product through the No. 1 heat exchanger 22, and heat the reaction solution flowing into the photothermal methanol reforming module 4. The reaction is a weakly exothermic reaction, so the temperature will rise after the reaction, and then pass through the No. 2 heat exchanger 24 to preheat the reaction solution.

[0107] The products after the photothermal methanol reforming module 4 mainly include hydrogen, carbon dioxide, a small amount of carbon monoxide, and incompletely reacted methanol vapor and water vapor. Furthermore, the carbon monoxide concentration of the product after the water vapor shift reactor 23 will be greatly reduced, and the gas is mainly composed of hydrogen and carbon dioxide. After passing through the carbon dioxide pressure swing adsorption device 27, hydrogen with a purity greater than 99.99% can be obtained, which is basically the same level as the hydrogen produced in the electrolysis process.

[0108] The photovoltaic module 3 - 1 is manufactured by a dicing process, wherein dicing structures formed by the dicing process are connected in series to form the photovoltaic module 3 - 1 .

[0109] Specifically, the photovoltaic module 3-1 adopts a dicing structure. Commercial cells are divided and manufactured, and connected in series to form the photovoltaic module 3-1. This design can reduce the external output current under concentrated light incidence and reduce the parasitic resistance loss of the photovoltaic cell.

[0110] The material of the photovoltaic fixing plate 3-2 includes copper or aluminum. Copper or aluminum materials with good thermal conductivity can transfer the waste heat generated by the photovoltaic power generation module 3 to the fluid in the internal fluid channel.

[0111] In the photothermal methanol reforming module 4, a high vacuum is maintained between the quartz glass tube (vacuum tube 4-1) and the thermochemical reaction tube 4-2 to avoid large convection and conduction heat losses caused by the presence of air inside. The surface of the thermochemical reaction tube 4-2 is coated with a solar absorption coating, which has a high absorption rate for full-spectrum solar energy. The catalyst bed 4-3 inside the thermochemical reaction tube 4-2 can be commercial granular Cu / ZnO / Al2O3, wherein the loading amount is determined according to the air velocity.

[0112] The beneficial effects of the present disclosure include: utilizing solar energy concentration and frequency division technology, coupling photovoltaic electrolysis and photothermal methanol reforming reaction, realizing the conversion of the full spectrum of solar energy into hydrogen, and the system has the advantages of high solar energy conversion efficiency and high purity of the obtained hydrogen. The present disclosure fully recycles the waste heat generated in the photovoltaic power generation process, which is used to preheat the reaction solution of the methanol reforming reaction, while reducing the operating temperature of the photovoltaic and improving the utilization efficiency of solar energy. The present disclosure uses both the photovoltaic (photovoltaic power generation module 3) and the photothermal part (photothermal methanol reforming module 4) for hydrogen production, introduces the methanol reforming reaction, and realizes the photothermal production of pure hydrogen through pressure swing adsorption and other forms.

[0113] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present disclosure, but the present disclosure is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and substance of the present disclosure, and these modifications and improvements are also considered to be within the scope of protection of the present disclosure.

Claims

1. A full-spectrum solar hydrogen production system coupled with photovoltaic and thermochemical technology, characterized in that: The full-spectrum hydrogen production system includes a light-collecting and frequency-dividing subsystem, a photovoltaic electrolysis subsystem, and a photothermal methanol reforming subsystem; Among them, the focusing and frequency division subsystem focuses and divides the incident full-spectrum sunlight, and then injects it into the photovoltaic electrolysis subsystem and the photothermal methanol reforming subsystem; the focusing and frequency division subsystem focuses the sunlight of the band matching the photovoltaic band gap and injects it into the photovoltaic electrolysis subsystem to convert it into electrical energy, thereby driving the electrolysis of water to produce hydrogen; the focusing and frequency division subsystem focuses the sunlight of the remaining bands and injects it into the photothermal methanol cracking subsystem to convert it into thermal energy, thereby driving the methanol / water reaction solution to carry out methanol reforming thermochemical reaction to produce hydrogen; the photovoltaic electrolysis subsystem is connected to the photothermal methanol reforming subsystem, and the photothermal methanol reforming subsystem recovers the waste heat generated in the photovoltaic power generation process for preheating the methanol / water reaction solution and cooling the photovoltaic.

2. A photovoltaic and thermochemical coupled full-spectrum solar hydrogen production system according to claim 1, characterized in that: The light-collecting and frequency-dividing subsystem includes a trough-type light-collecting mirror and a frequency-dividing light-collecting mirror; The trough concentrator is used to concentrate incident full-spectrum sunlight; the frequency-splitting concentrator is used to reflect the sunlight in the band of the full-spectrum sunlight that matches the photovoltaic band gap of the photovoltaic electrolysis subsystem to the photovoltaic power generation module of the photovoltaic electrolysis subsystem, and the frequency-splitting concentrator transmits the sunlight in the remaining bands to the photothermal methanol reforming module of the photothermal methanol reforming subsystem for conversion into thermal energy.

3. A photovoltaic and thermochemical coupled full-spectrum solar hydrogen production system according to claim 1, characterized in that: The photovoltaic electrolysis subsystem comprises a photovoltaic power generation module, a maximum power tracking device, a DC / DC converter and an electrolytic cell which are connected in sequence.

4. A photovoltaic and thermochemical coupled full-spectrum solar hydrogen production system according to claim 3, characterized in that: The photovoltaic power generation module comprises a photovoltaic component and a photovoltaic fixing plate; the photovoltaic component is arranged on the surface of the photovoltaic fixing plate; a fluid channel is arranged in the photovoltaic fixing plate; The photovoltaic module is used to convert incident sunlight of a wavelength matching its photovoltaic band gap into electrical energy; the photovoltaic fixing plate is used to fix the photovoltaic module and transfer the waste heat generated in the process of converting the photovoltaic module into electrical energy to the internal fluid channel for preheating the methanol / water reaction solution of the thermochemical reaction and cooling the photovoltaic module.

5. The photovoltaic and thermochemical coupled full-spectrum solar hydrogen production system according to claim 1, characterized in that: The photothermal methanol reforming subsystem includes a photothermal methanol reforming module, a methanol tank, a water tank, a methanol pump, a water pump, a methanol flow meter, a flow valve, a water flow meter, a No. 1 heat exchanger, a water vapor shift reactor, a No. 2 heat exchanger, a condenser, a gas-liquid separator, a carbon dioxide pressure swing adsorption device, a carbon dioxide storage tank and a gas storage tank; The methanol tank, methanol pump and methanol flowmeter are connected in sequence through a methanol pipeline; the water tank, water pump and water flowmeter are connected in sequence through a water pipeline, and are diverted through a No. 1 water valve, so that part of the water in the water pipeline merges with the methanol in the methanol pipeline to form a methanol / water reaction solution that enters the methanol / water pipeline; and the other part of the water flows into the downstream water pipeline; The inlet end of the fluid channel in the photovoltaic power generation module is connected to the methanol / water pipeline and the water pipeline respectively; the output end of the fluid channel is connected to the inlet end of the thermochemical reaction tube in the photothermal methanol reforming module through the liquid inlet pipeline, and is also connected to the electrolyzer through the water pipeline; The input end of the photothermal methanol reforming module is connected to the No. 1 heat exchanger, the No. 2 heat exchanger and the output end of the photovoltaic power generation module in sequence through a liquid inlet pipeline; the output end of the photothermal methanol reforming module is connected to the No. 1 heat exchanger, the water vapor shift reactor, the No. 2 heat exchanger, the condenser, the gas-liquid separator, the carbon dioxide pressure swing adsorption device and the gas storage tank in sequence through a liquid outlet pipeline.

6. A photovoltaic and thermochemical coupled full-spectrum solar hydrogen production system according to claim 5, characterized in that: The photothermal methanol reforming module comprises a vacuum tube, a thermochemical reaction tube and a catalyst bed; the thermochemical reaction tube is arranged in the vacuum tube; the catalyst bed is arranged in the thermochemical reaction tube; The vacuum tube is used to transmit sunlight and to maintain a vacuum environment between the vacuum tube and the thermochemical reaction tube; The thermochemical reaction tube is used to absorb incident sunlight and convert it into thermal energy, and transfer the heat to the catalyst bed; The catalyst bed is used to catalyze the methanol / water reaction solution to carry out a methanol reforming reaction.

7. A photovoltaic and thermochemical coupled full-spectrum solar hydrogen production system according to claim 2, characterized in that: The lower cut-off wavelength of the selective reflection band of the frequency-division condenser is 500 nm; the upper cut-off wavelength of the selective reflection band of the frequency-division condenser is the photon wavelength corresponding to the photovoltaic band gap energy.

8. A photovoltaic and thermochemical coupled full-spectrum solar hydrogen production system according to claim 2, characterized in that: The trough concentrator and the frequency-splitting concentrator are both parabolic structures; the photovoltaic power generation module is arranged in the middle position of the trough concentrator; the photothermal methanol reforming module is arranged at the focal position of the trough concentrator; the frequency-splitting concentrator is arranged between the photovoltaic power generation module and the photothermal methanol reforming module, and is used to reflect part of the band of sunlight reflected from the trough concentrator to the photovoltaic power generation module again, and transmit the remaining band of sunlight to the photothermal methanol reforming module.

9. A photovoltaic and thermochemical coupled full-spectrum solar hydrogen production system according to claim 2, characterized in that: The total width of the trough condenser is L1, the total width of the frequency-dividing condenser is L2, and the width of the photovoltaic power generation module is L PV , the outer diameter of the photothermal methanol reforming module is D1; The energy of photons of different wavelengths incident on the photovoltaic power generation module is expressed as: I PV (λ)=I PV,1 (λ)+I PV,2 (λ)+I PV,3 (l); The energy of photons of different wavelengths incident on the photothermal methanol reforming module is expressed as: I TR (λ)=I TR,4 (λ)+I TR,5 (λ)+I TR,6 (λ)+I TR,7 (l); Where λ is the wavelength, and the reflectivity of the trough condenser for photons of different wavelengths is ρ pc ; The reflectivity of the frequency-dividing condenser for photons of different wavelengths is ρ sbs , the transmittance is τ sbs ; The absorption rate of the photovoltaic power generation module for the incident light is α PV ; The absorption rate of the incident light by the photothermal methanol reforming module is α TR ; At different wavelengths, the incident power is I in (λ) condition, the photon energy of different wavelengths absorbed by the photovoltaic power generation module is expressed as: I PV (λ)=(L1ρ pc r sbs (λ)+(L PV -D1)t sbs (λ)+L2τ sbs (l)r pc r sbs (l))I in (la PV ; The energy of photons of different wavelengths absorbed by the CTM reforming module is expressed as: I TR (λ)=(L1ρ pc t sbs (λ)+L2ρ sbs (λ)+(L PV -D1)p sbs (λ)+L2τ sbs (l)r pc t sbs (λ)+D1)I in (la TR ; Among them, based on the above conditional formula, the energy of photons of different bands absorbed by the photovoltaic power generation module and the photothermal methanol reforming module can be obtained to calculate the electric energy generated by the photovoltaic power generation module and the heat provided for the methanol reforming reaction of the photothermal methanol reforming module.

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