Solar photovoltaic photo-thermal high-temperature water electrolysis hydrogen production system and hydrogen production method
Technical Field
The invention belongs to the field of solar heat collection and photovoltaic power generation hydrogen production by water electrolysis, and relates to a solar photovoltaic photo-thermal high-temperature hydrogen production system by water electrolysis and a hydrogen production method.
Background
With the development of human society, energy consumption in the aspects of industrial production, transportation, electricity consumption, heating and the like is increasing day by day. In the combustion and use process of fossil fuels, a large amount of CO is discharged2And pollutants, resulting in global warming and serious environmental pollution. Particularly, in recent years, the PM2.5 is seriously out of limits, and the public worry about the environmental problems is greatly aroused. The conflict between increasing energy demand and the ever-deteriorating environment is becoming more acute. Therefore, there is an urgent need to find new clean energy sources to change the current energy pattern based on fossil fuels to achieve the goal of reducingThe purpose of pollutant and greenhouse gas emission. Among the numerous new energy sources explored by people, hydrogen is a secondary energy source with high heat value, no pollution and no greenhouse gas generation. At present, the primary production process for hydrogen is natural gas reforming, which still produces CO2And the problems of environmental pollution and greenhouse effect also exist in the hydrogen production process. The water electrolysis hydrogen production is the reverse process of hydrogen and oxygen combustion to generate water, so that water can be decomposed without any pollution as long as certain energy is provided. Solar energy, wind energy, biomass energy and nuclear energy are clean primary energy sources, and the primary energy sources are utilized to produce hydrogen, so that the resource environmental pressure of fossil fuel can be solved from the source.
Solar energy is used as a renewable new energy source, and becomes an alternative energy source which is urgently needed to be developed by human beings due to the advantages of unlimited storage amount, existing universality, economy and the like. At present, solar thermal power generation technology and photovoltaic power generation technology are two most common modes for reasonably utilizing solar energy. Photovoltaic power generation has more the advantage for light and heat power generation now, simple structure, and the technology is mature, realizes easily, and light and heat has higher efficiency when solar energy turns into heat energy. However, although the potential of the solar energy industry is huge, clean and efficient, the solar power generation grid connection has a great problem due to the instability of sunlight, and the grid connection has great influence on a power grid due to great volatility, so that the development of an energy storage technology is needed. Therefore, it is very promising to store solar energy as a high-heat-density energy source. The solar water electrolysis hydrogen production is a promising implementation mode.
The current water electrolysis hydrogen production technology mainly comprises alkaline water electrolysis (AEC), proton exchange membrane electrolysis (PEM) and a Solid Oxide Electrolytic Cell (SOEC). The alkaline water electrolysis is superior in structure and cost, but the alkaline water electrolysis is gradually eliminated due to excessive electricity consumption, easy corrosion and explosion. The electrolysis efficiency of the proton exchange membrane is improved compared with the electrolysis efficiency of alkaline water, the electrolysis process is safe, a great amount of research is carried out at present, but the efficiency of the whole solar hydrogen production system is still not high, and the price of the proton exchange membrane is expensive, so that the industrial production of the proton exchange membrane is influenced to a certain extent. Compared with a proton exchange membrane, the solid oxide electrolytic cell has higher electrolytic efficiency which can reach 90 percent, and the price of the electrolytic cell material is lower because the porous ceramic is adopted, but the operating temperature of the solid oxide electrolytic cell needs high temperature of more than 800 degrees, and certain requirements are provided for the preparation process of the electrolytic cell material. In the electrolysis process, the temperature of the electrolysis solution exceeds 900 degrees, so that the electrodes fall off, the ohmic loss is greatly increased, and the electrolysis efficiency is greatly reduced. Therefore, the high temperature required by the electrolytic cell needs to be provided, and the temperature of the electrolytic water system is not overhigh.
However, the current hydrogen production system cannot meet the requirements, and the problem of low-temperature hydrogen production efficiency cannot be solved.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide a solar photovoltaic photo-thermal high-temperature water electrolysis hydrogen production system, which can prolong the service life of a solid oxide electrolytic cell on the premise of ensuring the efficiency and improve the economy of the solar hydrolysis system.
In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:
the invention discloses a solar photovoltaic photo-thermal high-temperature water electrolysis hydrogen production system, which comprises a heat supply unit, an electrolysis unit, a hydrogen production unit and a hydrogen collection unit;
the heat supply unit comprises a groove type solar heat pipe and a high-temperature molten salt storage tank and a low-temperature molten salt storage tank which are respectively connected with the groove type solar heat pipe;
the electrolysis unit comprises a photovoltaic cell array and a solid oxide electrolysis cell, and the photovoltaic cell array is connected with the solid oxide electrolysis cell through a DC/DC converter;
the hydrogen production unit comprises a water tank, a high-temperature steam generator, a low-temperature heat exchanger and a high-temperature heat exchanger; the water outlet of the water tank is connected with the water inlet of the low-temperature heat exchanger, the water outlet of the low-temperature heat exchanger is connected with the water inlet of the high-temperature steam generator through a pump I, and the air outlet of the high-temperature steam generator is connected with the steam inlet of the high-temperature heat exchanger;
the hydrogen collecting unit comprises a steam-water separator, an air inlet of the steam-water separator is connected with an air outlet of the low-temperature heat exchanger, and a water outlet of the steam-water separator is connected with the water tank;
the high-temperature molten salt storage tank is connected with the high-temperature steam generator through a pump II;
an oxygen outlet and a hydrogen outlet of the solid oxide electrolytic cell are respectively connected with a high-temperature heat exchanger, and a high-temperature steam outlet of the high-temperature heat exchanger is connected with the solid oxide electrolytic cell.
Preferably, the high-temperature steam generator is connected with the low-temperature molten salt storage tank, and the low-temperature molten salt subjected to heat exchange is conveyed into the low-temperature molten salt storage tank.
Preferably, a temperature sensor I is arranged on a gas inlet pipeline of the high-temperature heat exchanger.
Further preferably, when the gas temperature detected by the temperature sensor I is higher than 850 ℃, the temperature of the steam at the outlet of the high-temperature steam generator is reduced by reducing the flow of the high-temperature molten salt in the high-temperature steam generator; when the gas temperature detected by the temperature sensor I is lower than 850 degrees, the steam temperature at the outlet of the steam generator is increased by increasing the flow of the high-temperature molten salt in the high-temperature steam generator.
Preferably, a temperature sensor II for adjusting the temperature of the solid oxide electrolytic cell is arranged on a gas outlet pipeline of the high-temperature heat exchanger.
Preferably, the anode material of the solid oxide electrolytic cell is Ni-YSZ, the electrolyte material is YSZ, and the cathode material is LSM-YSZ; and the solid oxide electrolytic cell has a decay rate of less than 2% when operated at 800 ℃ for 1000 hours.
Further preferably, the incorporation of hydrogen gas into the electrolyzed water vapor places the Ni-YSZ electrode in a weakly reducing atmosphere to prevent electrode decay.
The invention also discloses a method for preparing hydrogen based on the solar photovoltaic photo-thermal high-temperature water electrolysis hydrogen production system, which comprises the following steps:
the water in the water tank absorbs the waste heat of the hydrogen and the oxygen through the low-temperature heat exchanger, when the temperature rises to the critical temperature, the water enters the high-temperature steam generator to exchange heat with the high-temperature molten salt to generate high-temperature water steam and low-temperature molten salt, and the low-temperature molten salt enters the low-temperature molten salt storage tank;
the low-temperature molten salt in the low-temperature molten salt storage tank absorbs solar radiation through the groove type solar heat pipe, the low-temperature molten salt is changed into high-temperature molten salt, the high-temperature molten salt is introduced into the high-temperature molten salt storage tank to be used for heat storage, high-temperature water vapor generated by heat exchange with the high-temperature molten salt enters the high-temperature heat exchanger to exchange heat with high-temperature hydrogen and oxygen obtained by electrolysis to reach the electrolysis temperature, then the high-temperature hydrogen and the high-temperature oxygen generated by high-temperature electrolysis enter the high-temperature heat exchanger to be cooled and released, then the high-temperature hydrogen and the high-temperature oxygen enter the steam-water separator after being cooled and.
Compared with the prior art, the invention has the following beneficial effects:
the invention discloses a solar photovoltaic photo-thermal high-temperature water electrolysis hydrogen production system, which takes a groove type solar thermal collector and fused salt stored by a fused salt double-tank energy storage system as a heat source, takes a photovoltaic cell matrix as an electrolysis power supply, and is connected with a solid oxide electrolytic cell through a DC/DC converter to realize power supply. In the system, a solid oxide electrolytic cell is connected with a high-temperature heat exchanger, the high-temperature heat exchanger exchanges heat between hydrogen produced by the solid oxide electrolytic cell and oxygen and water vapor, and 800-degree high-temperature water vapor can be provided for the solid oxide electrolytic cell, so that the temperature of the hydrogen and the oxygen is reduced; the groove type solar heat pipe is connected with the two molten salt storage tanks, and when sunlight has certain intensity, the groove type solar heat pipe heats the molten salt in the low-temperature molten salt storage tank and stores the molten salt in the high-temperature molten salt storage tank; the high-temperature molten salt storage tank is connected with the high-temperature steam generator, and the high-temperature steam generator exchanges heat between saturated water in the low-temperature heat exchanger and the molten salt to prepare high-temperature steam, and then the high-temperature steam is supplied to the high-temperature heat exchanger. The produced high-temperature hydrogen and high-temperature oxygen are subjected to twice heat exchange, the heat of high-temperature gas generated by electrolyzing water in a high-temperature electrolytic cell under large current is fully utilized, and the efficiency of the solar water electrolysis system is optimized and improved to a certain extent. The electrode poisoning caused by overhigh temperature of the high-temperature solid oxide electrolytic cell is systematically optimized, so that the service life of the electrolytic cell is prolonged under the condition of ensuring the efficiency, and the economical efficiency of a solar water electrolysis system is improved. Therefore, the system couples photovoltaic photo-thermal and high-temperature electrolysis, reasonably utilizes solar energy to carry out high-temperature hydrogen production, and avoids instability of direct solar power generation. Reasonably utilizes the current mature photo-thermal technology to solve the problems of low-temperature hydrogen production efficiency, environmental pollution and the like.
Drawings
FIG. 1 is a structural diagram of a solar photovoltaic photo-thermal high-temperature water electrolysis hydrogen production system of the invention;
wherein: 1 is a photovoltaic cell square matrix; 2 is a solid oxide electrolytic cell; 3, a trough type solar heat pipe; 4 is a high-temperature molten salt storage tank; 5 is a low-temperature molten salt storage tank; 6, a high-temperature steam generator; 7, a low-temperature heat exchanger; 8, a high-temperature heat exchanger; 9 a steam-water separator; 10, a water tank; 11 is a pump II; 12 is a pump I; 13 a temperature sensor I; 14 is a temperature sensor II; and 15 is a DC/DC converter.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
The invention is described in further detail below with reference to the accompanying drawings:
referring to fig. 1, a solar photovoltaic photo-thermal high-temperature water electrolysis hydrogen production system comprises a heat supply unit, an electrolysis unit, a hydrogen production unit and a hydrogen collection unit; the heat supply unit comprises a groove type solar heat pipe 3 and a high-temperature molten salt storage tank 4 and a low-temperature molten salt storage tank 5 which are respectively connected with the groove type solar heat pipe; the electrolysis unit comprises a photovoltaic cell array 1 and a solid oxide electrolysis cell 2, wherein the photovoltaic cell array 1 and the solid oxide electrolysis cell 2 are connected through a DC/DC converter 15; the hydrogen production unit comprises a water tank 10, a high-temperature steam generator 6, a low-temperature heat exchanger 7 and a high-temperature heat exchanger 8; the water outlet of the water tank 10 is connected with the water inlet of the low-temperature heat exchanger 7, the water outlet of the low-temperature heat exchanger 7 is connected with the water inlet of the high-temperature steam generator 6 through a pump I12, and the air outlet of the high-temperature steam generator 6 is connected with the steam inlet of the high-temperature heat exchanger 8; the hydrogen collecting unit comprises a steam-water separator 9, an air inlet of the steam-water separator 9 is connected with an air outlet of the low-temperature heat exchanger 7, and a water outlet of the steam-water separator 9 is connected with a water tank 10; the high-temperature molten salt storage tank 4 is connected with the high-temperature steam generator 6 through a pump II 11; an oxygen outlet and a hydrogen outlet of the solid oxide electrolytic cell 2 are respectively connected with the high-temperature heat exchanger 8, and a high-temperature steam outlet of the high-temperature heat exchanger 8 is connected with the solid oxide electrolytic cell 2.
The photovoltaic cell array 1 is connected with a DC/DC converter 15; the DC/DC converter 15 is connected with the solid oxide electrolytic cell 2 for power supply; the solid oxide electrolytic cell 2 is connected with the high-temperature heat exchanger 8, and the high-temperature heat exchanger 8 exchanges heat between hydrogen produced by the solid oxide electrolytic cell 2 and oxygen and water vapor, so as to provide 800-degree high-temperature water vapor for the solid oxide electrolytic cell 2 and reduce the temperature of the hydrogen and the oxygen; the groove type solar heat pipe 3 is connected with the two molten salt storage tanks, and when sunlight has certain intensity, the groove type solar heat pipe 3 heats the molten salt in the low-temperature molten salt storage tank 5 and stores the molten salt in the high-temperature molten salt storage tank 4; the high-temperature molten salt storage tank 4 is connected with the high-temperature steam generator 6, and the high-temperature steam generator 6 exchanges heat between saturated water in the low-temperature heat exchanger 7 and the molten salt to prepare high-temperature steam which is then supplied to the high-temperature heat exchanger 8;
the high-temperature heat exchanger 8 and the solid oxide electrolytic cell 2 are provided with three pipelines, wherein two pipelines are respectively used for conveying high-temperature hydrogen and high-temperature oxygen to the high-temperature heat exchanger 8 by the solid oxide electrolytic cell 2, and the other pipeline is used for conveying high-temperature water vapor to the solid oxide electrolytic cell 2 by the high-temperature heat exchanger 8;
the molten salt energy storage of the groove type solar heat pipe 3 adopts a double-tank energy storage system, when the irradiation is strong, the temperature of the solid oxide electrolytic cell 2 is increased, the control pump II 11 reduces the flow of the molten salt at the moment, stores a part of high-temperature molten salt, and when the irradiation intensity is weakened, the flow of the high-temperature molten salt is increased to improve the temperature of steam at the inlet of the high-temperature heat exchanger 8, so that the electrolysis efficiency is ensured; the pump I12 primarily powers the system cycle, supplementing the on-way resistance consumed.
The temperature sensor I13 is arranged at the inlet of the high-temperature heat exchanger 8 and is used for detecting the temperature of the electrolyzed hydrogen and oxygen, when the temperature exceeds 850 ℃, the flow of the high-temperature molten salt in the high-temperature steam generator 6 is reduced, the temperature of the steam at the outlet of the steam generator is reduced, when the temperature is lower than 850 ℃, the flow of the high-temperature molten salt is increased, and the temperature of the steam at the outlet of the high-temperature steam generator 6 is increased, so that the temperature of the solid oxide electrolytic cell 2 can be adjusted;
the temperature sensor II 14 is used for adjusting the temperature of the solid oxide electrolytic cell 2 and the temperature of steam at the inlet of the electrolytic cell, preventing the damage of the electrode caused by overhigh temperature and ensuring that the electrolytic cell works under the stable working condition
In the solid oxide electrolytic cell 2, a small amount of hydrogen is doped into electrolyzed water vapor, so that the Ni-YSZ electrode is ensured to be in a weak reduction atmosphere, and the electrode attenuation is prevented.
When the solar photovoltaic photo-thermal high-temperature water electrolysis hydrogen production system is used for producing hydrogen, the method comprises the following steps:
the water in the water tank 10 absorbs the waste heat of the hydrogen and the oxygen through the low-temperature heat exchanger 7, when the temperature rises to the critical temperature, the water enters the high-temperature steam generator 6 to exchange heat with the high-temperature molten salt to generate high-temperature steam and low-temperature molten salt, and the low-temperature molten salt enters the low-temperature molten salt storage tank 5;
the low-temperature molten salt in the low-temperature molten salt storage tank 5 absorbs solar radiation through the groove type solar heat pipe 3, the low-temperature molten salt is changed into high-temperature molten salt, the high-temperature molten salt is introduced into the high-temperature molten salt storage tank 4 for heat storage, high-temperature water vapor generated by heat exchange with the high-temperature molten salt enters the high-temperature heat exchanger 8 to exchange heat with high-temperature hydrogen and oxygen obtained by electrolysis to reach the electrolysis temperature, then the high-temperature water vapor enters the solid oxide electrolytic cell 2 to be electrolyzed at high temperature to generate high-temperature hydrogen and oxygen, the generated high-temperature hydrogen and oxygen enter the high-temperature heat exchanger 8 to be cooled and released, then the high-temperature hydrogen and the oxygen enter.
In conclusion, the invention takes the molten salt heat storage of the groove type solar heat collector as a heat source, one steam generator heats water, the photovoltaic array is an electrolysis power supply, the high-temperature solid oxide electrolytic cell, one high-temperature heat exchanger provides high-temperature steam for the electrolytic cell, one low-temperature heat exchanger recovers the residual heat for preheating the water in the water tank, and one hydrogen-steam separator is used for cooling and separating the produced hydrogen. Water in the water tank absorbs waste heat of hydrogen and oxygen through the low-temperature heat exchanger, the temperature rises to critical temperature, the water enters the high-temperature steam generator to exchange heat with high-temperature molten salt to generate high-temperature steam and low-temperature molten salt, the high-temperature steam finally enters the high-temperature heat exchanger to exchange heat with the electrolyzed high-temperature hydrogen and oxygen to reach the electrolysis temperature, and the water enters the solid oxide electrolytic cell to carry out high-temperature electrolysis to generate high-temperature hydrogen and oxygen. The invention relates to a system for efficiently producing hydrogen by utilizing solar photovoltaic photo-heat without pollution.
The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.