A system and method for producing hydrogen by combining photovoltaic thermal energy and electric energy

Abstract

The present invention proposes a system and method for producing hydrogen by using photovoltaic thermal energy and electric energy, including a photovoltaic power generation unit, an electrical conversion device and a plurality of photovoltaic panels, the electrical conversion device is used to convert solar energy into electric energy through photovoltaic panels; a waste heat recovery unit is used to absorb waste heat generated by solar radiation from photovoltaic panels through circulating heat storage fluid; a salinity gradient power generation unit includes a heat exchanger, an air gap distillation device and a reverse electrodialysis device, the air gap distillation device combines the heat exchanger and the waste heat recovery unit to input the heat storage medium into the heat exchanger, and performs concentration control and regeneration on the salt solution passed into the reverse electrodialysis device, and the reverse electrodialysis mechanism generates electricity by relying on the concentration gradient of the salt solution; an electrolytic hydrogen production unit is used to combine the excess photovoltaic power and the power generated by the salinity gradient power generation unit to participate in the electrolysis of water to produce hydrogen. The present invention produces hydrogen by photovoltaic power generation and salinity gradient power generation, thereby improving the overall utilization rate of photovoltaic energy.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic hydrogen production, and in particular to a system and method for combined hydrogen production using photovoltaic thermal energy and electric energy. Background Art

[0002] With the continuous growth of global energy demand and the enhancement of environmental protection awareness, the development and utilization of renewable energy has become a hot topic in current research. As a major renewable energy source, solar energy is inexhaustible. However, photovoltaic power generation systems face multiple challenges in practical applications, including low efficiency, waste heat management, and excess power utilization.

[0003] Photovoltaic power generation is the process of converting solar energy into electrical energy using the photoelectric effect. In the process of converting solar radiation energy into electrical energy, photovoltaic modules will generate a certain amount of waste heat. In photovoltaic modules, after the sunlight is absorbed, part of the light energy will be converted into electrical energy, while the other part will be absorbed by the module and converted into heat energy, causing the module to heat up. This part of heat energy will cause the temperature of the photovoltaic module to rise, thereby generating waste heat. The peak power temperature coefficient of photovoltaic modules is generally between -0.38% and -0.44% / ℃, that is, as the temperature rises, the output power of photovoltaic modules will decrease. In the process of solar photovoltaic power generation, while solar radiation is converted into electrical energy on the surface of the module, it will also cause some heat loss, resulting in reduced photovoltaic energy utilization efficiency.

[0004] In addition, when solar radiation is too strong, the power generation of the photovoltaic power generation system will exceed the load carrying capacity of the power system, resulting in some electricity being unable to be effectively incorporated into the power grid, resulting in power abandonment. In addition, the instability and temporal and spatial distribution of photovoltaic power generation also make it a major challenge to match the power between it and the power grid, further exacerbating the problem of power abandonment.

[0005] As a clean energy with high energy density and zero emissions, hydrogen energy has broad application prospects. Using water electrolysis to produce hydrogen technology, the excess electricity generated in the photovoltaic power generation process can be converted into hydrogen energy storage, thereby alleviating the problem of power abandonment. However, only using excess electricity to produce hydrogen still fails to fully utilize the waste heat resources in the photovoltaic power generation system.

[0006] In the process of hydrogen production by electrolysis, in order to improve the efficiency of hydrogen production, other power generation means are also used in the existing technology to generate electricity and combine with excess photovoltaic power to produce hydrogen. Reverse electrodialysis (RED) is a technology that uses salinity gradient to generate electricity. Through the migration of ions between high-concentration and low-concentration solutions, a potential difference is generated, thereby outputting electrical energy. However, during the long-term operation of the reverse electrodialysis system, as the concentration of the high-concentration solution decreases and the concentration of the low-concentration solution increases, the concentration gradient gradually decreases, resulting in a weakening of the output potential and current, affecting the system's continuous power generation capacity. If the waste heat in the photovoltaic power generation system can be used in reverse electrodialysis, the efficiency of salinity gradient power generation can be greatly improved.

[0007] Therefore, combining the waste heat generated during photovoltaic power generation with excess electricity for comprehensive utilization can not only improve energy utilization efficiency, but also significantly enhance the overall benefits of the photovoltaic power generation system. Summary of the invention

[0008] In view of this, the present invention proposes a system and method for jointly producing hydrogen using photovoltaic thermal energy and electric energy, which effectively utilizes the waste heat generated in the photovoltaic power generation process to generate salinity gradient electricity, and utilizes the excess electric energy of photovoltaic power generation to produce hydrogen, thereby improving the overall utilization rate of photovoltaic energy.

[0009] The technical solution of the present invention is achieved in this way:

[0010] In one aspect, the present invention provides a system for producing hydrogen by using photovoltaic thermal energy and electric energy, comprising:

[0011] A photovoltaic power generation unit, comprising an electrical conversion device and a plurality of photovoltaic panels electrically connected thereto, wherein the electrical conversion device is used to convert solar energy into electrical energy through the photovoltaic panels;

[0012] A waste heat recovery unit is used to absorb waste heat generated by solar radiation from the photovoltaic panel through a circulating heat storage fluid;

[0013] A salinity gradient power generation unit comprises a heat exchanger, an air gap distillation device and a reverse electrodialysis device, wherein the reverse electrodialysis device is sequentially connected to the air gap distillation device, the heat exchanger and the waste heat recovery unit, and the air gap distillation device combines the heat exchanger and the waste heat recovery unit to input heat storage medium into the heat exchanger to control and regenerate the concentration of the salt solution introduced into the reverse electrodialysis device, and the reverse electrodialysis device generates electricity by relying on the concentration gradient of the salt solution;

[0014] The electrolytic hydrogen production unit is connected to the electrical conversion device and the salinity gradient power generation unit, and is used to combine the excess photovoltaic power and the power generated by the salinity gradient power generation unit to participate in the electrolysis of water to produce hydrogen.

[0015] On the basis of the above technical scheme, preferably, the waste heat recovery unit includes a heat exchange plate, a liquid inlet pipe, a liquid outlet pipe and a water pump. The heat exchange plate is fixedly arranged on the lower surface of the photovoltaic panel, and the two ends of the water pump are respectively connected to the liquid inlet pipe and the liquid outlet pipe. The end of the liquid inlet pipe away from the water pump is connected to the liquid inlet end of the heat exchange plate, and the end of the liquid outlet pipe away from the water pump is connected to the liquid outlet end of the heat exchange plate. The water pump is used to circulate the heat storage fluid in the heat fluid circuit formed by the liquid inlet pipe, the heat exchange plate and the liquid outlet pipe.

[0016] On the basis of the above technical solution, preferably, the reverse electrodialysis device comprises:

[0017] Cation exchange membranes and anion exchange membranes, wherein the cation exchange membranes and anion exchange membranes are alternately arranged to form a plurality of membrane pairs;

[0018] An anode and a cathode are respectively located at two ends of the membrane pair, and the anode and the cathode are used to provide electrodes for electrochemical reactions;

[0019] An electrolyte, disposed around the anode and cathode, for maintaining the balance of the electrochemical reaction and the conductivity;

[0020] The high concentration solution flow channel and the low concentration solution flow channel are alternately arranged between the membrane pairs to form a salinity gradient. The high concentration solution flow channel is used to transport a high concentration solution, and the low concentration solution flow channel is used to transport a low concentration solution. The high concentration solution flow channel and the low concentration solution flow channel are connected to an air gap distillation device.

[0021] On the basis of the above technical solution, preferably, the air gap distillation device comprises a box, a cold flow pipeline, a cooler, a hot flow pipeline, a condensation plate, an evaporator, a first delivery pump, a second delivery pump and a third delivery pump;

[0022] The hot flow pipe, evaporator, condensation plate and cold flow pipe are stacked inside the box;

[0023] The inlet end of the cold flow pipeline is connected to the outlet ends of the high-concentration solution flow channel and the low-concentration solution flow channel through the cooling liquid and the first delivery pump;

[0024] The outlet end of the condensation plate is connected to the liquid inlet end of the low-concentration solution flow channel through a second delivery pump;

[0025] The outlet end of the heat flow pipeline is connected to the liquid inlet end of the high concentration solution flow channel through a third delivery pump;

[0026] The outlet end of the cold flow pipeline and the inlet end of the hot flow pipeline are connected to the heat exchanger, and the heat exchanger is connected in series to the hot fluid loop.

[0027] Further, preferably, the liquid outlet end of the low-concentration solution flow channel is also connected to the output end of the second delivery pump.

[0028] On the basis of the above technical solution, preferably, the heat exchanger includes a shell, which has independent liquid inlet chambers, liquid outlet chambers and heat exchange chambers. The top surface of the shell is provided with a hot fluid inlet connected to the heat exchange chamber, and the bottom surface of the shell is provided with a hot fluid outlet connected to the heat exchange chamber. The hot fluid inlet and the hot fluid outlet are connected in series on the hot fluid circuit, the outlet end of the cold flow pipe is connected to the liquid inlet chamber, and the inlet end of the hot flow pipe is connected to the liquid outlet chamber. A plurality of heat exchange tube bundles are arranged in the heat exchange chamber, and the two ends of the heat exchange tube bundle are respectively connected to the liquid inlet chamber and the liquid outlet chamber, and a plurality of partitions are staggered in the heat exchange chamber along the liquid flow direction.

[0029] On the basis of the above technical solution, preferably, the electrolytic hydrogen production unit includes an electrolytic cell and a constant voltage circuit battery, the input end of the constant voltage circuit is electrically connected to the output end of the electrical conversion device, the input end of the battery is electrically connected to the reverse electrodialysis device, the output end of the battery is electrically connected to the input end of the constant voltage circuit, the constant voltage circuit is used to stabilize the electricity generated by the salinity gradient and the excess photovoltaic power, and the output end of the constant voltage circuit is electrically connected to the input end of the electrolytic cell.

[0030] Further, preferably, the constant voltage circuit includes a filter, a switching tube, a high-frequency converter transformer, a high-frequency rectifier filter, a pulse modulator and a driving amplifier, the filter filters the input voltage, the switching tube is used to convert the filtered voltage into a high-frequency voltage, the high-frequency converter transformer is used to convert the high-frequency voltage into a set voltage, and the high-frequency rectifier filter is used to output the stable voltage required by the electrolyzer; the switching tube is controlled by the pulse modulator and the driving amplifier, and when the output voltage changes, the sampling signal from the output end generates an error signal through the comparison circuit, and the error signal adjusts the duty cycle of the switching tube through the pulse modulator to ensure that the electrolysis voltage of the combined electrolysis hydrogen production is maintained at the required stable value.

[0031] On the basis of the above technical solution, preferably, it also includes a control platform, which includes a power monitoring module, a control module and a data processing module. The power monitoring module is used to monitor the power generation of the photovoltaic power generation unit, the data processing module is used to calculate and balance the grid load, and the control module is used to connect the excess electric energy to the constant voltage circuit when the total power generation exceeds the load of the connected power system.

[0032] In a second aspect, the present invention further discloses a method for producing hydrogen by using photovoltaic thermal energy and electric energy, which utilizes the photovoltaic thermal energy and electric energy combined hydrogen production system described in the first aspect, and comprises the following steps:

[0033] S1. Monitor whether the total amount of photovoltaic power generation exceeds the load carrying capacity of the power grid;

[0034] S2. When it does not exceed, it is connected to the grid. When it exceeds, the number of lines that need to be cut off to balance the grid is calculated, and the corresponding number of lines that flow to the grid are cut off, and the electrolytic hydrogen production unit is connected;

[0035] S3, monitoring the temperature of the heat storage fluid in the waste heat recovery unit, and when the temperature of the heat storage fluid is greater than the temperature of the salt solution, circulating the heat storage fluid in the waste heat recovery unit into the heat exchanger;

[0036] S4, adjusting the concentration of the salt solution introduced into the reverse electrodialysis device through an air gap distillation device and a heat exchanger, restoring the working solution concentration of the salt solution, and generating electricity based on the concentration gradient of the salt solution;

[0037] S5. The electricity generated by the concentration gradient of the salt solution is connected to the electrolytic hydrogen production unit, and combined with the excess photovoltaic electricity to produce hydrogen by electrolysis.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] (1) The reverse electrodialysis device of the present invention utilizes the concentration gradient of the salt solution to generate electricity, and the formation and maintenance of this concentration gradient depends on the operation of the air gap distillation device. The air gap distillation device uses the waste heat provided by the heat exchanger to distill and concentrate the salt solution, thereby maintaining the concentration gradient required for reverse electrodialysis. This process ensures that the salinity gradient power generation unit can generate electricity continuously and efficiently; the salinity gradient power generation unit effectively utilizes the waste heat generated by the photovoltaic panel by combining the air gap distillation device and the heat exchanger. This utilization method not only improves the thermal energy utilization rate of the entire system, but also improves the power generation efficiency; by using the excess electricity generated in the photovoltaic power generation process for water electrolysis to produce hydrogen, it effectively alleviates the problem that the excess electricity cannot be absorbed by the power grid, reduces the phenomenon of power abandonment, and improves the comprehensive benefits of photovoltaic power generation and hydrogen production through waste heat recovery and multi-energy complementarity (photovoltaic power and salinity gradient power), while improving the overall utilization rate of photovoltaic energy;

[0040] (2) The salinity gradient power generation unit utilizes renewable energy and waste heat, reducing environmental pollution and resource consumption. Compared with traditional power generation methods, this method is more environmentally friendly and helps reduce carbon footprint and protect the ecological environment. The salinity gradient power generation unit achieves efficient power generation by utilizing the waste heat of the photovoltaic system and the concentration gradient of the salt solution. It not only improves the overall energy utilization efficiency of the system and reduces energy waste, but also enhances the stability and economic benefits of the system through multi-energy complementarity and sustainable utilization.

[0041] (3) Through the combined use of a heat exchanger and a waste heat recovery unit, the salt solution flowing out of the reverse electrodialysis device passes through a cooler, then enters the cold flow pipe from bottom to top, absorbs the condensation heat of the steam, then passes through a heat exchanger, is heated by the low-grade heat brought by the heat storage fluid, and then enters the hot flow pipe under the action of gravity, passes through the porous medium (hydrophobic material, such as sponge) of the evaporator, and the steam evaporates and diffuses into the entire porous medium and pore gaps before condensing, then condenses on the condensation plate and flows out, mixes with a certain amount of low-concentration effluent and then recovers to the required concentration, and the remaining high-concentration effluent recovers to the required concentration, ensuring that the salt solution has a higher concentration gradient, improving the salinity gradient power generation efficiency, and thus improving the hydrogen production efficiency.

[0042] (4) The hydrogen production system disclosed in the present invention utilizes a photovoltaic power generation device to generate electrical energy, and supplies it to an electrolyzer after being processed by an electrical conversion device. The reverse electrodialysis device generates electricity through a salinity gradient and stores the electrical energy in a battery. The constant voltage circuit stabilizes the electrical energy generated by the photovoltaic power generation and the reverse electrodialysis device to ensure the stability of the electrical energy input to the electrolyzer, thereby improving the efficiency and reliability of hydrogen production by electrolysis. Through photovoltaic power generation and reverse electrodialysis power generation, the system can make full use of renewable energy and achieve green hydrogen production.

[0043] (5) The constant voltage circuit achieves efficient voltage stabilization of input electrical energy through filtering, high-frequency conversion and closed-loop control. Its design not only ensures the stability of the working voltage of the electrolyzer during the electrolytic hydrogen production process, but also responds quickly to voltage changes and provides constant electrical energy output. This efficient and stable power conversion and management method improves the overall performance and reliability of the combined hydrogen production system.

[0044] (6) The control platform realizes real-time monitoring and intelligent management of the power generation of photovoltaic power generation units through the coordinated work of power monitoring, data processing and control modules. When the power generation exceeds the load demand of the power grid, the excess power can be efficiently directed to the constant voltage circuit for the electrolysis hydrogen production process, maximizing the use of renewable energy and improving the energy efficiency and economic benefits of the system. This design not only optimizes the management and distribution of power, but also enhances the flexibility and reliability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0046] Figure 1 It is a schematic diagram of the planar structure of the photovoltaic thermal energy and electric energy combined hydrogen production system disclosed in the present invention;

[0047] Figure 2 It is a schematic diagram of the planar structure of the salinity gradient power generation unit disclosed in the present invention;

[0048] Figure 3 It is a principle diagram of the constant voltage circuit disclosed in the present invention;

[0049] Reference numerals:

[0050] 1. Photovoltaic power generation unit; 11. Electrical conversion device; 12. Photovoltaic panel; 2. Waste heat recovery unit; 3. Salinity gradient power generation unit; 31. Heat exchanger; 32. Air gap distillation device; 33. Reverse electrodialysis device; 4. Electrolytic hydrogen production unit; 21. Heat exchange plate; 22. Liquid inlet pipeline; 23. Liquid outlet pipeline; 24. Water pump; 331. Cation exchange membrane; 332. Anion exchange membrane; 333. Anode; 334. Cathode; 335. Electrolyte; 336. High concentration solution flow channel; 337. Low concentration solution flow channel solution flow channel; 321, box; 322, cold flow pipeline; 323, cooler; 324, hot flow pipeline; 325, condensation plate; 326, evaporator; 327, first delivery pump; 328, second delivery pump; 329, third delivery pump; 311, shell; 312, liquid inlet chamber; 313, liquid outlet chamber; 314, heat exchange chamber; 315, hot fluid inlet; 316, hot fluid outlet; 317, partition; 318, heat exchange tube bundle; 41, electrolytic cell; 42, constant voltage circuit; 43, battery. DETAILED DESCRIPTION

[0051] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] like Figure 1 As shown, combined Figure 2 The present invention discloses a system for producing hydrogen by combining photovoltaic thermal energy and electric energy, including a photovoltaic power generation unit 1, a waste heat recovery unit 2, a salinity gradient power generation unit 3 and an electrolytic hydrogen production unit 4.

[0053] Specifically, the photovoltaic power generation unit 1 includes an electrical conversion device 11 and a plurality of photovoltaic panels 12 electrically connected thereto. The electrical conversion device 11 is used to convert solar energy into electrical energy through the photovoltaic panels 12. Specifically, the electrical conversion device 11 is preferably a DC / AC converter.

[0054] The waste heat recovery unit 2 is connected to the photovoltaic panel 12 and is used to absorb the waste heat generated by the photovoltaic panel 12 due to solar radiation through the circulating heat storage fluid. The heat storage fluid provides the prerequisite for salinity gradient power generation by absorbing the waste heat of the photovoltaic panel 12.

[0055] The salinity gradient power generation unit 3 includes a heat exchanger 31, an air gap distillation device 32 and a reverse electrodialysis device 33. The reverse electrodialysis device 33 is connected to the air gap distillation device 32, the heat exchanger 31 and the waste heat recovery unit in sequence. The air gap distillation device 32 combines the heat exchanger 31 and the waste heat recovery unit 2 to input the heat storage medium into the heat exchanger 31, and performs concentration control and regeneration on the salt solution passed into the reverse electrodialysis device 33. The reverse electrodialysis mechanism generates electricity by relying on the concentration gradient of the salt solution.

[0056] In this embodiment, the reverse electrodialysis device 33 generates electricity using the concentration gradient of the salt solution, and the formation and maintenance of this concentration gradient depends on the operation of the air gap distillation device 32. The air gap distillation device 32 distills and concentrates the salt solution through the waste heat provided by the heat exchanger 31, thereby maintaining the concentration gradient required for reverse electrodialysis. This process ensures that the salinity gradient power generation unit 3 can generate electricity continuously and efficiently, thereby more efficiently meeting the needs of hydrogen production.

[0057] The salinity gradient power generation unit 3 effectively utilizes the waste heat generated by the photovoltaic panel 12 by combining the air gap distillation device 32 and the heat exchanger 31. This utilization method not only improves the thermal energy utilization rate of the entire system, but also reduces the temperature increase of the photovoltaic panel 12 caused by the inability to dissipate the waste heat, thereby improving the efficiency of photovoltaic power generation.

[0058] The salinity gradient power generation unit 3 utilizes renewable energy and waste heat, reducing environmental pollution and resource consumption. Compared with traditional power generation methods, this method is more environmentally friendly and helps reduce carbon footprint and protect the ecological environment. The salinity gradient power generation unit 3 achieves efficient power generation by utilizing the waste heat of the photovoltaic system and the concentration gradient of the salt solution. It not only improves the overall energy utilization efficiency of the system and reduces energy waste, but also enhances the stability and economic benefits of the system through multi-energy complementarity and sustainable utilization.

[0059] The electrolytic hydrogen production unit 4 is connected to the electrical conversion device 11 and the salinity gradient power generation unit 3, and is used to combine the excess photovoltaic power and the power generated by the salinity gradient power generation unit 3 to participate in the electrolysis of water to produce hydrogen.

[0060] By using the excess electricity generated in the photovoltaic power generation process for the electrolysis of water to produce hydrogen, the problem of excess electricity being unable to be absorbed by the power grid is effectively alleviated, and the phenomenon of power abandonment is reduced. The comprehensive benefits of photovoltaic power generation are improved through waste heat recovery and multi-energy complementation (photovoltaic power and salinity gradient power). In summary, the present invention solves the problems of waste heat management and power abandonment in traditional photovoltaic systems by making efficient use of the waste heat and excess electricity from photovoltaic power generation, and significantly improves energy utilization efficiency and the overall benefits of the system.

[0061] As some preferred embodiments, the waste heat recovery unit 2 includes a heat exchange plate 21 , a liquid inlet pipe 22 , a liquid outlet pipe 23 and a water pump 24 .

[0062] The heat exchange plate 21 is fixedly arranged on the lower surface of the photovoltaic panel 12. The main function of the heat exchange plate 21 is to absorb the heat generated by the photovoltaic panel 12 during the power generation process. This heat usually increases the temperature of the photovoltaic panel 12, affecting its power generation efficiency. By providing the heat exchange plate 21, this waste heat can be effectively transferred to the heat storage fluid to achieve the recovery and utilization of heat energy.

[0063] The two ends of the water pump 24 are respectively connected to the liquid inlet pipe 22 and the liquid outlet pipe 23. The end of the liquid inlet pipe 22 away from the water pump 24 is connected to the liquid inlet end of the heat exchange plate 21, and the end of the liquid outlet pipe 23 away from the water pump 24 is connected to the liquid outlet end of the heat exchange plate 21. The water pump 24 is used to circulate the heat storage fluid in the heat fluid loop formed by the liquid inlet pipe 22, the heat exchange plate 21 and the liquid outlet pipe 23.

[0064] The water pump 24 is the power source of the entire heat fluid loop, responsible for driving the heat storage fluid to circulate in the liquid inlet pipe 22, the heat exchange plate 21 and the liquid outlet pipe 23. Through the operation of the water pump 24, the heat storage fluid can continuously flow through the heat exchange plate 21, absorb the waste heat of the photovoltaic panel 12, and use the recovered heat energy for salinity gradient power generation, and then produce hydrogen through salinity gradient power generation, thereby improving the efficiency of photovoltaic power generation and hydrogen production.

[0065] The present invention shows a structural mode of a reverse electrodialysis device 33 , specifically, including a cation exchange membrane 331 , an anion exchange membrane 332 , an anode 333 , a cathode 334 , an electrolyte 335 , a high concentration solution flow channel 336 and a low concentration solution flow channel 337 .

[0066] The cation exchange membrane 331 and the anion exchange membrane 332 are arranged alternately to form a plurality of membrane pairs; the cation exchange membrane 331 allows cations to pass through and blocks anions, while the anion exchange membrane 332 allows anions to pass through and blocks cations. This arrangement can form an ion selective conduction path for the electrolyte solution, thereby generating a potential difference.

[0067] The anode 333 and the cathode 334 are located at the two ends of the membrane pair, respectively, and are used to provide electrodes for electrochemical reactions; these electrodes promote the migration of ions in the electrolyte 335 under the action of an external electric field, thereby generating current. The potential difference between the anode 333 and the cathode 334 drives the electrodialysis process.

[0068] The electrolyte 335 is disposed around the anode 333 and the cathode 334 to maintain the balance of the electrochemical reaction and the conductivity. The electrolyte 335 mainly conducts current through the movement of ions to ensure the continuation of the electrodialysis process. The electrolyte 335 is usually a solution containing a high concentration of electrolytes, such as hydrochloric acid (HCl), sulfuric acid or sodium hydroxide (NaOH) solution.

[0069] The high concentration solution flow channel 336 and the low concentration solution flow channel 337 are alternately arranged between the membrane pairs to form a salinity gradient. The high concentration solution flow channel 336 is used to transport a high concentration solution, and the low concentration solution flow channel 337 is used to transport a low concentration solution. The high concentration solution flow channel 336 and the low concentration solution flow channel 337 are connected to the air gap distillation device 32.

[0070] The high concentration solution flows through the high concentration solution flow channel 336 between the cation exchange membrane 331 and the anion exchange membrane 332, providing a high concentration of dissolved ions, which together with the low concentration solution form a salinity gradient, driving the migration of ions through the membrane pair, thereby generating a potential difference.

[0071] The low-concentration solution flows through the low-concentration solution flow channel 337 between the cation exchange membrane 331 and the anion exchange membrane 332, providing low-concentration dissolved ions, which cooperate with the high-concentration solution to form a salinity gradient, drive the migration of ions through the membrane pair, and thus generate a potential difference.

[0072] In this embodiment, the high concentration solution is generally an aqueous solution containing high concentration salt (such as sodium chloride, NaCl), which can be seawater, concentrated brine or industrial wastewater.

[0073] Reverse electrodialysis (RED) uses a concentration gradient to generate a potential difference. The greater the concentration gradient, the higher the potential difference generated. However, as the run time passes, the concentration of the high-concentration solution continues to decrease and the concentration of the low-concentration solution continues to increase, which causes the concentration gradient to decrease. As the concentration gradient decreases, the potential difference decreases and the current output decreases. The electrolysis of water to produce hydrogen requires a stable and sufficiently high potential (usually more than 1.23 volts) and current. As the concentration gradient decreases, the potential and current generated by the RED device will decrease.

[0074] To this end, the present invention connects the high concentration solution flow channel 336 and the low concentration solution flow channel 337 to the air gap distillation device 32, which can effectively maintain and manage the concentration gradient between the salt solutions.

[0075] The present invention shows a preferred structural mode of the air gap distillation device 32, specifically, including a box 321, a cold flow pipeline 322, a cooler 323, a hot flow pipeline 324, a condensation plate 325, an evaporator 326, a first delivery pump 327, a second delivery pump 328 and a third delivery pump 329;

[0076] The hot flow pipe 324, the evaporator 326, the condensation plate 325 and the cold flow pipe 322 are stacked inside the box 321;

[0077] The inlet end of the cold flow pipeline 322 is connected to the outlet ends of the high concentration solution flow channel 336 and the low concentration solution flow channel 337 through the cooling liquid and the first delivery pump 327;

[0078] The outlet end of the condensation plate 325 is connected to the liquid inlet end of the low-concentration solution flow channel 337 through the second delivery pump 328;

[0079] The outlet end of the heat flow pipe 324 is connected to the liquid inlet end of the high concentration solution flow channel 336 through the third delivery pump 329;

[0080] The outlet end of the cold flow pipe 322 and the inlet end of the hot flow pipe 324 are connected to the heat exchanger 31, and the heat exchanger 31 is connected in series to the hot fluid loop.

[0081] With the above technical solution, the salt solution flowing out of the reverse electrodialysis device 33 passes through the cooler 323, and then enters the cold flow pipe 322 from bottom to top to absorb the condensation heat of the steam. The salt solution flowing out here is a mixed solution, specifically a mixed solution of a high-concentration solution converted into a low-concentration solution and a low-concentration solution converted into a high-concentration solution. After the mixed solution passes through the cooler, the mixed liquid can take away the condensation heat, so that the subsequent steam can continue to condense on the condensation plate, and on the other hand, it is also helpful to better absorb the waste heat brought by the heat storage fluid. The mixed solution then passes through the heat exchanger 31, is heated by the low-grade heat brought by the heat storage fluid, and then enters the hot flow pipe 324 under the action of gravity, passes through the porous medium (hydrophobic material, such as sponge) of the evaporator 326, and the steam evaporates and diffuses into the entire porous medium and pore gap before condensation, and then condenses and flows out on the condensation plate 325, mixes with a certain amount of low-concentration effluent and then recovers to the required concentration, and the remaining high-concentration effluent has recovered to the required concentration.

[0082] As some preferred embodiments, the liquid outlet of the low-concentration solution flow channel 337 is also connected to the output end of the second delivery pump 328. This arrangement allows the concentration of the low-concentration solution to meet the concentration required for salinity gradient power generation.

[0083] As some preferred embodiments, the heat exchanger 31 includes a shell 311, and the shell 311 has a liquid inlet chamber 312, a liquid outlet chamber 313 and a heat exchange chamber 314 that are independent of each other. The top surface of the shell 311 is provided with a hot fluid inlet 315 connected to the heat exchange chamber 314, and the bottom surface of the shell 311 is provided with a hot fluid outlet 316 connected to the heat exchange chamber 314. The hot fluid inlet 315 and the hot fluid outlet 316 are connected in series in the hot fluid circuit, thereby setting, The heat storage fluid that absorbs heat in the waste heat recovery unit 2 can circulate into the heat exchange chamber 314, the outlet end of the cold flow pipe 322 is connected to the liquid inlet chamber 312, and the inlet end of the hot flow pipe 324 is connected to the liquid outlet chamber 313. A plurality of heat exchange tube bundles 318 are arranged in the heat exchange chamber 314, and the two ends of the heat exchange tube bundle 318 are respectively connected to the liquid inlet chamber 312 and the liquid outlet chamber 313, and a plurality of partitions 317 are staggered in the heat exchange chamber 314 along the liquid flow direction.

[0084] In the present embodiment, the liquid inlet chamber 312 is used to pass a low-temperature salt solution. After the salt solution passes through the heat exchange tube bundle 318, it absorbs the heat of the heat storage fluid inside the heat exchange chamber 314, and flows out from the liquid outlet chamber 313 to form a high-temperature salt solution, ensuring that the salt solution is evaporated and concentrated in the air gap distillation device 32, thereby restoring the original concentration of the high-concentration solution converted into a low-concentration solution, and restoring the original concentration of the low-concentration solution converted into a high-concentration solution, ensuring that the salt solution has a higher concentration gradient, thereby improving the salinity gradient power generation efficiency, and thereby improving the hydrogen production efficiency.

[0085] The present invention shows a preferred structural form of the electrolytic hydrogen production unit 4. Specifically, the electrolytic hydrogen production unit 4 includes an electrolytic cell 41, a constant voltage circuit 42 and a battery 43. The electrolytic cell 41 is used to perform a water electrolysis reaction, and decomposes water molecules to generate hydrogen and oxygen through electrical energy. The input end of the constant voltage circuit 42 is electrically connected to the output end of the electrical conversion device 11, the input end of the battery 43 is electrically connected to the reverse electrodialysis device 33, and the output end of the battery 43 is electrically connected to the input end of the constant voltage circuit 42. The constant voltage circuit 42 is used to stabilize the electricity generated by the salinity gradient and the photovoltaic excess electric energy, and the output end of the constant voltage circuit 42 is electrically connected to the input end of the electrolytic cell 41.

[0086] With the above technical solution, the reverse electrodialysis device 33 is used to generate electric energy by utilizing the salinity gradient, and the electric energy is input into the storage battery 43 for storage for subsequent use. When needed, the storage battery 43 outputs the stored electric energy to the constant voltage circuit 42, and the constant voltage circuit 42 performs voltage stabilization on the electric energy again to ensure the stability of the electric energy required by the electrolytic cell 41. The constant voltage circuit 42 outputs stable electric energy, which is directly supplied to the electrolytic cell 41 to support the electrolysis reaction.

[0087] The hydrogen production system disclosed in the present invention utilizes a photovoltaic power generation device to generate electric energy, and supplies the electric energy to an electrolyzer 41 after being processed by an electric conversion device 11. The reverse electrodialysis device 33 generates electric energy through a salinity gradient and stores the electric energy in a storage battery 43. The constant voltage circuit 42 performs voltage stabilization on the electric energy generated by the photovoltaic power generation and the reverse electrodialysis device 33, thereby ensuring the stability of the electric energy input to the electrolyzer 41 and improving the efficiency and reliability of hydrogen production by electrolysis. Through photovoltaic power generation and reverse electrodialysis power generation, the system can make full use of renewable energy and realize green hydrogen production.

[0088] Refer to the attached Figure 3 As shown, the constant voltage circuit 42 disclosed in the present invention includes a filter, a switch tube, a high-frequency converter transformer, a high-frequency rectifier filter, a pulse modulator and a driving amplifier. The filter filters the input voltage to eliminate noise and unstable components in the voltage and provide a relatively pure DC voltage.

[0089] The switching tube is used to convert the filtered voltage into a high-frequency voltage. The switching tube generally uses a high-speed switching device, such as MOSFET or IGBT.

[0090] The high-frequency converter transformer is used to convert the high-frequency voltage into a set voltage. Through the action of the transformer, the voltage can be increased or decreased to the required working voltage of the electrolytic cell 41.

[0091] The high-frequency rectifier filter is used to output the stable voltage required by the electrolytic cell 41; the switching tube is controlled by the pulse modulator and the driving amplifier. When the output voltage changes, the sampling signal from the output end generates an error signal through the comparison circuit. The error signal adjusts the duty cycle of the switching tube through the pulse modulator to ensure that the electrolysis voltage of the combined electrolysis hydrogen production is maintained at the required stable value.

[0092] The constant voltage circuit 42 achieves efficient voltage stabilization of input electric energy through filtering, high-frequency conversion and closed-loop control. Its design not only ensures the stability of the working voltage of the electrolyzer 41 during the electrolytic hydrogen production process, but also responds quickly to voltage changes and provides constant electric energy output. This efficient and stable electric energy conversion and management method improves the overall performance and reliability of the combined hydrogen production system.

[0093] The hydrogen production system of the present invention also includes a control platform, which includes a power monitoring module, a control module and a data processing module. The power monitoring module is used to monitor the power generation of the photovoltaic power generation unit 1. In some embodiments, the power output data of the photovoltaic power generation unit 1 is obtained through sensors and monitoring equipment. The data processing module is used to calculate and balance the load of the power grid, analyze the load of the current power grid through an algorithm, and compare it with the power generation of the photovoltaic power generation unit 1 to determine the balance of power supply and demand. The control module is used to control the distribution of electric energy. When the total power generation exceeds the load of the connected power system, the excess electric energy is connected to the constant voltage circuit 42.

[0094] By adopting the above technical solution, the control platform realizes real-time monitoring and intelligent management of the power generation of the photovoltaic power generation unit 1 through the coordinated work of power monitoring, data processing and control modules. When the power generation exceeds the grid load demand, the excess power can be efficiently guided to the constant voltage circuit 42 for the electrolytic hydrogen production process, maximizing the use of renewable energy and improving the energy efficiency and economic benefits of the system. This design not only optimizes the management and distribution of power, but also enhances the flexibility and reliability of the system.

[0095] The present invention also discloses a method for producing hydrogen by using photovoltaic thermal energy and electric energy, which utilizes the photovoltaic thermal energy and electric energy combined hydrogen production system, and includes the following steps:

[0096] S1. Monitor whether the total amount of photovoltaic power generation exceeds the load carrying capacity of the power grid; in some specific methods, the total amount of photovoltaic power generation can be monitored in real time using a power monitoring module. The monitored power generation is compared with the load carrying capacity of the power grid to determine whether it exceeds the load capacity of the power grid.

[0097] S2. When the total amount of photovoltaic power generation does not exceed the load carrying capacity of the power grid, the electric energy is integrated into the power grid. When it exceeds the load carrying capacity, the amount of electricity flowing to the photovoltaic panels 12 that needs to be cut off to balance the power grid is calculated, and the corresponding amount of electricity flowing to the power grid is cut off, and the electrolytic hydrogen production unit 4 is connected;

[0098] S3, monitoring the temperature of the heat storage fluid in the waste heat recovery unit 2, and when the temperature of the heat storage fluid is greater than the temperature of the salt solution, circulating the heat storage fluid in the waste heat recovery unit 2 into the heat exchanger 31;

[0099] S4, adjusting the concentration of the salt solution introduced into the reverse electrodialysis device 33 through the air gap distillation device 32 and the heat exchanger 31, restoring the working solution concentration of the salt solution, and generating electricity based on the concentration gradient of the salt solution;

[0100] S5. The electricity generated by the concentration gradient of the salt solution is connected to the electrolytic hydrogen production unit 4, and combined with the excess photovoltaic power to produce hydrogen by electrolysis.

[0101] Through real-time monitoring and calculation, the intelligent distribution of electricity is realized to ensure the stability of the power grid and the efficient use of photovoltaic power generation. The waste heat recovery unit 2 and the heat exchanger 31 are used to fully recover and utilize the waste heat resources in the system to improve the overall energy efficiency. Through reverse electrodialysis and concentration gradient power generation technology, the concentration difference of the salt solution is converted into electrical energy to further improve the energy utilization rate. The electrical energy from different sources (surplus photovoltaic energy and concentration gradient power generation energy) is combined for electrolysis hydrogen production to achieve flexible and efficient hydrogen production.

[0102] The present invention adopts a simple, effective and low-cost method to absorb and transfer the waste heat of photovoltaic power generation, combines it with the efficient method of converting salinity gradient to produce electricity and hydrogen, and regulates excess electricity to directly participate in hydrogen production, which greatly reduces the loss of electricity in photovoltaic power generation and improves the overall power generation efficiency.

[0103] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A system for producing hydrogen by using photovoltaic thermal energy and electric energy, characterized in that: include: A photovoltaic power generation unit (1) comprises an electrical conversion device (11) and a plurality of photovoltaic panels (12) electrically connected thereto, wherein the electrical conversion device (11) is used to convert solar energy into electrical energy via the photovoltaic panels (12); A waste heat recovery unit (2) is used to absorb waste heat generated by solar radiation from the photovoltaic panel (12) through a circulating heat storage fluid; A salinity gradient power generation unit (3) comprises a heat exchanger (31), an air gap distillation device (32) and a reverse electrodialysis device (33), wherein the reverse electrodialysis device (33) is connected to the air gap distillation device (32), the heat exchanger (31) and the waste heat recovery unit (2) in sequence, and the air gap distillation device (32) combines the heat exchanger (31) and the waste heat recovery unit (2) to input heat storage medium into the heat exchanger (31), and performs concentration control and regeneration on the salt solution introduced into the reverse electrodialysis device (33), wherein the reverse electrodialysis device (33) generates electricity based on the concentration gradient of the salt solution; The electrolytic hydrogen production unit (4) is connected to the electrical conversion device (11) and the salinity gradient power generation unit (3) and is used to combine the excess photovoltaic power and the power generated by the salinity gradient power generation unit (3) to participate in the electrolysis of water to produce hydrogen; The waste heat recovery unit (2) comprises a heat exchange plate (21), a liquid inlet pipe (22), a liquid outlet pipe (23) and a water pump (24); the heat exchange plate (21) is fixedly arranged on the lower surface of the photovoltaic panel (12); two ends of the water pump (24) are respectively connected to the liquid inlet pipe (22) and the liquid outlet pipe (23); one end of the liquid inlet pipe (22) away from the water pump (24) is connected to the liquid inlet end of the heat exchange plate (21); one end of the liquid outlet pipe (23) away from the water pump (24) is connected to the liquid outlet end of the heat exchange plate (21); the water pump (24) is used to circulate the heat storage fluid in the heat fluid loop formed by the liquid inlet pipe (22), the heat exchange plate (21) and the liquid outlet pipe (23); The reverse electrodialysis device (33) comprises: Cation exchange membranes (331) and anion exchange membranes (332), wherein the cation exchange membranes (331) and anion exchange membranes (332) are alternately arranged to form a plurality of membrane pairs; An anode (333) and a cathode (334), respectively located at two ends of the membrane pair, wherein the anode (333) and the cathode (334) are used to provide electrodes for electrochemical reactions; An electrolyte (335) is disposed around the anode (333) and the cathode (334) to maintain the balance of the electrochemical reaction and the conductivity; A high concentration solution flow channel (336) and a low concentration solution flow channel (337) are alternately arranged between the membrane pairs to form a salinity gradient, wherein the high concentration solution flow channel (336) is used to transport a high concentration solution, and the low concentration solution flow channel (337) is used to transport a low concentration solution, and the high concentration solution flow channel (336) and the low concentration solution flow channel (337) are connected to the air gap distillation device (32); The air gap distillation device (32) comprises a housing (321), a cold flow pipeline (322), a cooler (323), a hot flow pipeline (324), a condensation plate (325), an evaporator (326), a first delivery pump (327), a second delivery pump (328) and a third delivery pump (329); The hot flow pipe (324), the evaporator (326), the condensation plate (325) and the cold flow pipe (322) are stacked inside the box (321); The inlet end of the cold flow pipeline (322) is connected to the liquid outlet ends of the high-concentration solution flow channel (336) and the low-concentration solution flow channel (337) through the cooling liquid and the first delivery pump (327); The outlet end of the condensation plate (325) is connected to the liquid inlet end of the low-concentration solution flow channel (337) through a second delivery pump (328); The outlet end of the heat flow pipeline (324) is connected to the liquid inlet end of the high concentration solution flow channel (336) through a third delivery pump (329); The outlet end of the cold flow pipeline (322) and the inlet end of the hot flow pipeline (324) are connected to the heat exchanger (31), and the heat exchanger (31) is connected in series to the hot fluid loop.

2. The photovoltaic thermal energy and electric energy combined hydrogen production system as claimed in claim 1, characterized in that: The liquid outlet end of the low-concentration solution flow channel (337) is also connected to the output end of the second delivery pump (328).

3. The system for producing hydrogen by using photovoltaic thermal energy and electric energy as claimed in claim 1, characterized in that: The heat exchanger (31) comprises a shell (311), wherein the shell (311) has a liquid inlet chamber (312), a liquid outlet chamber (313) and a heat exchange chamber (314) which are independent of each other, a hot fluid inlet (315) which is connected to the heat exchange chamber (314) is arranged on the top surface of the shell (311), and a hot fluid outlet (316) which is connected to the heat exchange chamber (314) is arranged on the bottom surface of the shell (311), and the hot fluid inlet (315) and the hot fluid outlet (316) are connected to the heat exchange chamber (314). 6) are connected in series on the hot fluid circuit, the outlet end of the cold flow pipe (322) is connected to the liquid inlet chamber (312), the inlet end of the hot flow pipe (324) is connected to the liquid outlet chamber (313), a plurality of heat exchange tube bundles (318) are arranged in the heat exchange chamber (314), the two ends of the heat exchange tube bundle (318) are respectively connected to the liquid inlet chamber (312) and the liquid outlet chamber (313), and a plurality of partitions (317) are staggeredly arranged in the heat exchange chamber (314) along the liquid flow direction.

4. The system for producing hydrogen by using photovoltaic thermal energy and electric energy as claimed in claim 1, characterized in that: The electrolytic hydrogen production unit (4) comprises an electrolytic cell (41), a constant voltage circuit (42) and a storage battery (43), wherein the input end of the constant voltage circuit (42) is electrically connected to the output end of the electrical conversion device (11), the input end of the storage battery (43) is electrically connected to the reverse electrodialysis device (33), the output end of the storage battery (43) is electrically connected to the input end of the constant voltage circuit (42), the constant voltage circuit (42) is used to perform voltage stabilization processing on electricity generated by salinity gradient and photovoltaic excess electric energy, and the output end of the constant voltage circuit (42) is electrically connected to the input end of the electrolytic cell (41).

5. The system for producing hydrogen by using photovoltaic thermal energy and electric energy as claimed in claim 4, characterized in that: The constant voltage circuit (42) includes a filter, a switch tube, a high-frequency converter transformer, a high-frequency rectifier filter, a pulse modulator and a drive amplifier. The filter filters the input voltage. The switch tube is used to convert the filtered voltage into a high-frequency voltage. The high-frequency converter transformer is used to convert the high-frequency voltage into a set voltage. The high-frequency rectifier filter is used to output the stable voltage required by the electrolytic cell (41). The switch tube is controlled by the pulse modulator and the drive amplifier. When the output voltage changes, the sampling signal from the output end generates an error signal through the comparison circuit. The error signal adjusts the duty cycle of the switch tube through the pulse modulator to ensure that the electrolysis voltage of the combined electrolysis hydrogen production is maintained at the required stable value.

6. The system for producing hydrogen by using photovoltaic thermal energy and electric energy as claimed in claim 4, characterized in that: It also includes a control platform, which includes a power monitoring module, a control module and a data processing module. The power monitoring module is used to monitor the power generation of the photovoltaic power generation unit, the data processing module is used to calculate and balance the grid load, and the control module is used to connect the excess electric energy to the constant voltage circuit when the total power generation exceeds the load of the connected power system.

7. A method for producing hydrogen by using photovoltaic thermal energy and electric energy, which utilizes the photovoltaic thermal energy and electric energy combined hydrogen production system as claimed in any one of claims 1 to 6, characterized in that: The steps include: S1. Monitor whether the total amount of photovoltaic power generation exceeds the load carrying capacity of the power grid; S2. When it does not exceed, it is connected to the grid. When it exceeds, the number of lines that need to be cut off to balance the grid is calculated, and the corresponding number of lines that flow to the grid are cut off, and the electrolytic hydrogen production unit is connected; S3, monitoring the temperature of the heat storage fluid in the waste heat recovery unit, and when the temperature of the heat storage fluid is greater than the temperature of the salt solution, circulating the heat storage fluid in the waste heat recovery unit into the heat exchanger; S4, adjusting the concentration of the salt solution introduced into the reverse electrodialysis device through an air gap distillation device and a heat exchanger, restoring the working solution concentration of the salt solution, and generating electricity based on the concentration gradient of the salt solution; S5. The electricity generated by the concentration gradient of the salt solution is connected to the electrolytic hydrogen production unit, and combined with the excess photovoltaic electricity to produce hydrogen by electrolysis.

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