Physical and chemical coupled high-efficiency long-time energy storage system and method

Abstract

The invention provides a physically and chemically coupled high-efficiency long-time energy storage system and method.The physically and chemically coupled high-efficiency long-time energy storage system comprises an electrolytic tank hydrogen production system, a Carnot cell energy storage circulation system, a fuel cell power generation system and a Carnot cell energy release circulation system, and the electrolytic tank hydrogen production system is used for converting first electric energy into hydrogen energy to be stored; the Carnot battery energy storage circulating system is used for converting the second electric energy into heat energy and cold energy for storage; the fuel cell power generation system is used for generating third electric energy by utilizing an electrochemical reaction between the hydrogen prepared by the electrolytic tank hydrogen production system and air, realizing conversion from hydrogen energy to the third electric energy, and combusting residual hydrogen tail gas and air tail gas in the electrochemical reaction to release heat so as to generate combustion heat; and the Carnot battery energy release circulation system is used for cooling the energy release first air by using the stored cold energy and then compressing the first air to obtain energy release second air, and heating the energy release fourth air by using the combustion heat and the stored heat energy and then expanding and doing work to generate fourth electric energy so as to realize conversion from the combustion heat, the heat energy and the cold energy to the fourth electric energy. According to the invention, physical and chemical energy storage technologies are coupled, a large-scale long-time energy storage technology of a Carnot cell is taken as a basic load, an electrolytic cell and fuel cell technology is taken as a regulation and control load aiming at source-load side fluctuation, rapid power consumption and supply are realized, and an efficient and flexible long-time energy storage system is created.

Description

Technical Field

[0001] The present invention relates to the field of energy storage technology, and in particular to a physical and chemical coupled high-efficiency long-term energy storage system and method. Background Art

[0002] Energy storage technology plays an important role in coping with the intermittent nature of renewable energy generation and the volatility of user loads. Its main requirements are as follows:

[0003] Long-term energy storage: In order to cope with the long-term and cross-seasonal energy storage needs of renewable energy generation, it is necessary to build a long-term energy storage system. Many existing energy storage systems (such as lithium batteries, etc.) can usually only meet the energy storage needs of a few hours, and it is difficult to achieve long-term energy storage and supply.

[0004] Large-scale energy storage: Traditional energy storage methods such as electrochemical energy storage and capacitors face significant cost, volume and safety challenges in large-scale energy storage, and are unable to meet the needs of ultra-large-scale energy storage, especially when combined with large-scale renewable energy power stations, and cannot achieve the ideal energy storage scale.

[0005] Rapid response: Some energy storage systems (such as pumped storage) have a certain lag in rapid response and cannot provide rapid energy replenishment when the power grid needs instantaneous adjustment, which limits their application in scenarios with frequent fluctuations in the power system and rapid response requirements.

[0006] In general, there is an urgent need for a large-scale, long-term energy storage system with rapid response capabilities to cope with the intermittent nature of renewable energy generation and the volatility of user loads, but existing energy storage technologies cannot meet the above requirements at the same time.

[0007] As a new type of physical energy storage technology, Carnot battery can convert electrical energy into heat and cold energy for storage through the reverse Brayton cycle when there is excess electricity, and convert heat and cold energy into electrical energy through the Brayton cycle when renewable energy generation is insufficient. It has the advantages of high energy storage density, high efficiency and long energy storage time, and is suitable for large-scale long-term energy storage needs. However, since the working process of Carnot battery includes multiple links such as air compression and expansion, and involves the storage of heat and cold energy, the startup and conversion time is long, and it is impossible to start and stop or adjust the output power extremely quickly, which limits its application in flexible peak regulation; in addition, due to the partial heat energy loss caused by the heat exchange temperature difference, the maximum temperature of the air in the energy release stage of the Carnot battery drops, and often cannot reach the maximum temperature of the air in the energy storage stage, resulting in reduced power generation and reduced efficiency of the system.

[0008] As efficient chemical energy storage technologies, electrolyzers and solid oxide fuel cells (SOFCs) can convert electricity into hydrogen energy through electrochemical reactions, and directly generate electricity using the electrochemical reaction of hydrogen and air at high temperatures. They have the characteristics of fast response, strong regulation ability, and long energy storage time, and are suitable for meeting peak power demand and long-term energy storage needs. However, SOFCs operate at high temperatures (600°C - 1000°C), producing a large amount of high-temperature exhaust gas containing unused fuel, and the waste heat needs to be effectively utilized to improve energy utilization. Summary of the invention

[0009] In view of this, the present invention provides a physically and chemically coupled high-efficiency long-term energy storage system and method, combining the technical advantages of Carnot cells, electrolytic cells and fuel cells to at least partially solve the above technical problems.

[0010] One aspect of the present invention provides a physical and chemical coupled high-efficiency long-term energy storage system, comprising:

[0011] The electrolytic cell hydrogen production system is used to utilize the first electrical energy to decompose water to generate hydrogen, so as to realize the conversion of the first electrical energy into hydrogen energy, and store the hydrogen;

[0012] The Carnot battery energy storage cycle system is used to compress the second energy storage air with the second electric energy to form the third energy storage air with high temperature and high pressure, store the air heat energy of the third energy storage air through heat exchange to form the fourth energy storage air, and expand the fifth energy storage air to form the sixth energy storage air with low temperature, store the air cold energy of the sixth energy storage air through heat exchange to realize the conversion of the second electric energy into heat energy and cold energy;

[0013] The fuel cell power generation system is used to generate a third electric energy by an electrochemical reaction between the hydrogen produced by the electrolytic cell hydrogen production system and air, thereby realizing the conversion of hydrogen energy into the third electric energy, and to burn the remaining hydrogen tail gas and air tail gas in the electrochemical reaction to release heat and generate combustion heat;

[0014] The Carnot battery energy release cycle system is used to utilize the cold energy stored in the Carnot battery energy storage cycle system to cool the first energy-releasing air and then compress it to obtain the third energy-releasing air, and utilize the combustion heat and the thermal energy stored in the Carnot battery energy storage cycle system to heat the fourth energy-releasing air twice to obtain the sixth energy-releasing air, and then utilize the sixth energy-releasing air to expand and do work to generate fourth electrical energy, so as to realize the conversion of combustion heat, thermal energy and cold energy into fourth electrical energy.

[0015] According to an embodiment of the present invention:

[0016] The electrolytic cell hydrogen production system comprises an electrolytic cell and a hydrogen tank, wherein the electrolytic cell is used to decompose water to generate hydrogen using the first electrical energy, and the hydrogen tank is used to store the hydrogen;

[0017] The Kano battery energy storage cycle system includes an energy storage compressor, an energy storage high-temperature heat exchanger, a heat storage high-temperature tank, a heat storage low-temperature tank, an energy storage regenerator, an energy storage expander, an energy storage low-temperature heat exchanger, a cold storage high-temperature tank, and a cold storage low-temperature tank. The energy storage compressor is used to use the second electric energy to compress the second energy storage air to form a high-temperature and high-pressure energy storage third air. The energy storage high-temperature heat exchanger is used to exchange heat between the energy storage third air and the molten salt medium in the heat storage low-temperature tank. The molten salt medium is heated and stored in the heat storage high-temperature tank. The energy storage third air forms a low-temperature and high-pressure energy storage fourth air after heat exchange. The energy storage regenerator is used to exchange heat between the fourth energy storage air and the first energy storage air. The first energy storage air is heated up to form the second energy storage air. The fourth energy storage air is cooled down to form the fifth energy storage air. The energy storage expander is used to expand the fifth energy storage air to form the sixth energy storage air in a low-temperature state. The energy storage low-temperature heat exchanger is used to exchange heat between the sixth energy storage air and the n-pentane medium in the cold storage high-temperature tank. The n-pentane medium is cooled and stored in the cold storage low-temperature tank. The sixth energy storage air returns to normal temperature and pressure after heat exchange and is used as the first energy storage air for the next cycle.

[0018] The fuel cell power generation system includes a fuel cell and a burner, wherein the fuel cell is used for electrochemical reaction, and the burner is used for burning the remaining hydrogen tail gas and air tail gas in the electrochemical reaction to release heat and generate combustion heat;

[0019] The energy release circulation system of the Carnot battery includes an energy-releasing low-temperature heat exchanger, a cold storage high-temperature tank, a cold storage low-temperature tank, an energy-releasing compressor, an energy-releasing high-temperature heat exchanger, a heat storage high-temperature tank, a heat storage low-temperature tank, a gas heat exchanger, an energy-releasing expander, an energy-releasing heat regenerator, and an energy-releasing radiator. The energy-releasing low-temperature heat exchanger is used to exchange heat between the first energy-releasing air and the n-pentane medium in the cold storage low-temperature tank. The n-pentane medium enters the cold storage high-temperature tank after heating. The first energy-releasing air is cooled to produce the second energy-releasing air. The energy-releasing compressor is used to compress the second energy-releasing air to obtain the third energy-releasing air with high pressure. The energy-releasing high-temperature heat exchanger is used to exchange heat between the fourth energy-releasing air and the molten metal in the heat storage high-temperature tank. The molten salt is used for heat exchange, and the molten salt is cooled and then enters the heat storage low-temperature tank. The fourth energy-releasing air is heated to form the fifth energy-releasing air. The gas heat exchanger is used to use the combustion heat to heat the fifth energy-releasing air to form the sixth energy-releasing air. The energy-releasing expander is used to use the sixth energy-releasing air to expand and do work to form the seventh energy-releasing air. The energy-releasing heat regenerator is used to exchange heat between the seventh energy-releasing air and the third energy-releasing air. The third energy-releasing air is heated to form the fourth energy-releasing air. The seventh energy-releasing air is cooled to form the eighth energy-releasing air. The energy-releasing radiator is used to dissipate the eighth energy-releasing air to room temperature as the first energy-releasing air for the next cycle.

[0020] The electrolytic cell adopts a proton exchange membrane electrolytic cell or an alkaline electrolytic cell;

[0021] The fuel cell uses a solid oxide fuel cell.

[0022] According to an embodiment of the present invention, the gas heat exchanger includes a first gas heat exchanger and a second gas heat exchanger connected in sequence;

[0023] The first part of the third energy-releasing air at the outlet of the energy-releasing compressor flows through the high-temperature energy-releasing heat exchanger to be heated once to form the fifth energy-releasing air, and then continues to flow through the first fuel gas heat exchanger to be heated twice to form the first part of the sixth energy-releasing air;

[0024] The second part of the energy-releasing third air at the outlet of the energy-releasing compressor flows through the second fuel gas heat exchanger to be heated to form the second part of the energy-releasing sixth air;

[0025] The heated first part of the energy-releasing sixth air and the second part of the energy-releasing sixth air together form the energy-releasing sixth air and enter the energy-releasing expander. According to an embodiment of the present invention, the hot end inlet of the first gas heat exchanger is connected to the outlet of the burner, and the hot end outlet of the first gas heat exchanger is connected to the hot end inlet of the second gas heat exchanger;

[0026] The outlet of the energy-releasing compressor is directly or indirectly connected to the cold end inlet of the energy-releasing high-temperature heat exchanger, the cold end outlet of the energy-releasing high-temperature heat exchanger is connected to the cold end inlet of the first gas heat exchanger, and the cold end outlet of the first gas heat exchanger is connected to the inlet of the energy-releasing expander;

[0027] The outlet of the energy-releasing compressor is communicated with the cold-end inlet of the second gas heat exchanger, and the cold-end outlet of the second gas heat exchanger is communicated with the inlet of the energy-releasing expander.

[0028] According to an embodiment of the present invention, the fuel cell power generation system further comprises a preheater, which is used to preheat hydrogen and air by using the combustion heat of the burner before the electrochemical reaction, and the inlet of the preheater is connected to the hot end outlet of the gas heat exchanger;

[0029] The preheater includes a first preheater and a second preheater, the preheater is used to preheat hydrogen before the electrochemical reaction, and the second preheater is used to preheat air before the electrochemical reaction.

[0030] According to an embodiment of the present invention, the energy releasing heat regenerator is used to utilize the waste heat of air expansion at the outlet of the energy releasing expander to preheat the energy releasing third air before entering the energy releasing high temperature heat exchanger;

[0031] The cold end inlet of the energy releasing heat regenerator is connected to the outlet of the energy releasing compressor, and the cold end outlet of the energy releasing heat regenerator is connected to the cold end inlet of the energy releasing high temperature heat exchanger;

[0032] The hot end inlet of the energy releasing heat regenerator is communicated with the outlet of the energy releasing expander, and the hot end outlet of the energy releasing heat regenerator is communicated with the hot end inlet of the energy releasing low-temperature heat exchanger.

[0033] According to an embodiment of the present invention, the electrolytic cell hydrogen production system also includes a hydrogen compressor and a hydrogen heat exchanger, wherein the hydrogen compressor is used to compress the produced hydrogen to obtain compressed hydrogen, and the hydrogen heat exchanger is used to transfer the hydrogen compression heat generated during the hydrogen compression process to the Carnot battery energy storage cycle system.

[0034] According to an embodiment of the present invention, the Carnot battery energy storage cycle system is also used to: preheat the first part of the energy storage first air before entering the energy storage compressor using the hydrogen compression heat introduced by the hydrogen heat exchanger;

[0035] The energy storage regenerator is used to preheat the second part of the energy storage first air before entering the energy storage compressor by using the residual heat of air compression at the outlet of the energy storage high-temperature heat exchanger.

[0036] According to an embodiment of the present invention, the outlet of the energy storage cryogenic heat exchanger is connected to the cold end inlet of the hydrogen heat exchanger, and the cold end outlet of the hydrogen heat exchanger is connected to the inlet of the energy storage compressor;

[0037] The outlet of the energy storage low-temperature heat exchanger is connected to the cold end inlet of the energy storage regenerator, and the cold end outlet of the energy storage regenerator is connected to the inlet of the energy storage compressor;

[0038] The hot end outlet of the energy storage high temperature heat exchanger is connected to the hot end inlet of the energy storage regenerator, and the hot end outlet of the energy storage regenerator is connected to the inlet of the energy storage expander.

[0039] Another aspect of the present invention provides an energy storage method, comprising:

[0040] Decomposing water to generate hydrogen using the first electrical energy, so as to convert the first electrical energy into hydrogen energy for storage;

[0041] The second electric energy is used to compress the second energy storage air to form the third energy storage air, the air heat energy of the third energy storage air is heat exchanged and stored to form the fourth energy storage air, and the fifth energy storage air is used to expand and do work to form the sixth energy storage air in a low temperature state, and the air cold energy of the sixth energy storage air is heat exchanged and stored, so as to convert the second electric energy into heat energy and cold energy for storage;

[0042] The electrochemical reaction of hydrogen and air is used to generate the third electrical energy, so as to realize the conversion of hydrogen energy into the third electrical energy, and the remaining hydrogen tail gas and air tail gas in the electrochemical reaction are burned to release heat, thereby generating combustion heat;

[0043] The first energy-releasing air is cooled by storing cold energy and then compressed to obtain the third energy-releasing air. The fourth energy-releasing air is heated twice by using the heat of combustion and thermal energy to obtain the sixth energy-releasing air. The sixth energy-releasing air is then expanded to do work to generate the fourth electrical energy, thereby realizing the conversion of the heat of combustion, thermal energy and cold energy into the fourth electrical energy.

[0044] According to an embodiment of the present invention, the above system realizes efficient coupling of physical energy storage and chemical energy storage through the coordinated work of electrolytic cells, fuel cells and Carnot batteries, can flexibly adjust the power and energy form of energy storage and energy release, meet the rapid response requirements of peak power, and provide long-term and stable energy supply for user-side loads, which is suitable for long-term, efficient and flexible energy storage application scenarios of renewable energy. The system uses Carnot batteries, a large-scale long-term energy storage technology, as the basic load, and uses electrolytic cells and fuel cell technologies as control loads for source-load fluctuations to achieve rapid power consumption and supply, creating an efficient and flexible long-term energy storage system. Specifically, Carnot batteries store electrical energy in the form of heat energy and cold energy, and have long-term, large-scale energy storage capabilities; electrolytic cells store electrical energy in the form of hydrogen energy, and have long-term, fast-response energy storage capabilities. The above system combines the characteristics of the two energy storage technologies, can effectively make up for the shortcomings of existing energy storage technologies, and better cope with the volatility of renewable energy and the changing needs of user loads. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0046] Figure 1 A system structure diagram of an electrolytic cell hydrogen production system and a Carnot battery energy storage cycle system in an energy storage stage according to an embodiment of the present invention is schematically shown;

[0047] Figure 2 The system structure diagram of the fuel cell power generation system and the Carnot battery energy release cycle system in the energy release stage according to an embodiment of the present invention is schematically shown;

[0048] Figure 3 Schematically shows an energy flow diagram between systems according to an embodiment of the present invention;

[0049] Figure 4 The operation flow chart of the energy storage method according to an embodiment of the present invention is schematically shown. DETAILED DESCRIPTION

[0050] Below, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of embodiments of the present invention. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of concepts of the present invention.

[0051] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0052] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0053] When using expressions such as "at least one of A, B, and C, etc.", they should generally be interpreted according to the meaning of the expression commonly understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0054] In view of the technical requirements of energy storage technology in long-term energy storage, large-scale energy storage, and high-efficiency energy storage, Carnot batteries can be used in related technologies. As a new type of physical energy storage technology, Carnot batteries can convert electrical energy into heat and cold energy for storage through the reverse Brayton cycle when there is excess electricity, and convert heat and cold energy into electrical energy through the Brayton cycle when renewable energy generation is insufficient. It has the advantages of high energy storage density, high efficiency, and long energy storage time, and is suitable for large-scale long-term energy storage needs. However, since the working process of Carnot batteries includes multiple links such as air compression and expansion, and involves the storage of heat and cold energy, the startup and conversion time is long, and the output power cannot be started or adjusted extremely quickly, which limits its application in flexible peak regulation; in addition, due to the partial heat energy loss caused by the heat exchange temperature difference, the maximum temperature of the air in the energy release stage of the Carnot battery drops, and it often cannot reach the maximum temperature of the air in the energy storage stage, resulting in a reduction in system power generation and reduced efficiency.

[0055] In view of the technical requirements of energy storage technology in terms of long-term energy storage and rapid response energy storage, the relevant technologies, for example, can use electrolytic cells and solid oxide fuel cells (SOFC). As efficient chemical energy storage technologies, electrolytic cells and solid oxide fuel cells (SOFC) can convert electricity into hydrogen energy through electrochemical reactions, and directly generate electricity by electrochemical reactions of hydrogen and air at high temperatures. They have the characteristics of fast response, strong regulation ability, and long energy storage time, and are suitable for dealing with peak power demand and long-term energy storage demand. However, SOFC has a high operating temperature (600°C-1000°C), which produces a large amount of high-temperature exhaust gas containing unused fuel, and the waste heat needs to be effectively utilized to improve energy utilization.

[0056] To solve these problems, an embodiment of the present invention provides an energy storage system to achieve efficient long-term energy storage by physical and chemical coupling.

[0057] The energy storage system of the embodiment of the present invention includes an electrolytic cell hydrogen production system (chemical energy storage), a Carnot battery energy storage cycle system (physical energy storage), a fuel cell power generation system (chemical energy storage), and a Carnot battery energy release cycle system (physical energy storage).

[0058] Among them, the electrolytic cell hydrogen production system is used to utilize the first electrical energy to decompose water to generate hydrogen, so as to convert the first electrical energy into hydrogen energy for storage.

[0059] For example, in an electrolytic cell hydrogen production system, the electrolytic cell can be used to use the first electrical energy to decompose water through electrochemical action to generate hydrogen and store it in a hydrogen tank at room temperature and high pressure (e.g., 45°C, 240 bar), thereby realizing the conversion of electrical energy into hydrogen energy.

[0060] Among them, the Carnot battery energy storage cycle system is used to use the second electric energy to compress the first energy storage air to form a high-temperature and high-pressure energy storage third air, and to store the air heat energy of the third energy storage air through heat exchange to form the fourth energy storage air, and to use the fifth energy storage air to expand and do work to form the sixth energy storage air in a low-temperature state, and to store the air cold energy of the sixth energy storage air through heat exchange, so as to convert the second electric energy into heat energy and cold energy and store them.

[0061] For example, the Carnot battery energy storage cycle system can use the second electric energy to drive the compressor to compress the second energy storage air into the third energy storage air in a high temperature and high pressure state (for example, 565.41 ℃, 3.72 bar), and use the third energy storage air to heat the molten salt medium in the thermal storage low temperature tank. After the molten salt medium is heated, it flows into the thermal storage high temperature tank for storage. After the heat exchange, the fifth energy storage air expands and does work to form the sixth energy storage air in a low temperature state (for example, -55.81 ℃), and the sixth energy storage air is used to cool the n-pentane medium in the thermal storage high temperature tank. After the n-pentane medium is cooled, it flows into the thermal storage low temperature tank for storage, so as to convert the second electric energy into heat energy and cold energy and store them.

[0062] Among them, the fuel cell power generation system is used to generate a third electrical energy through the electrochemical reaction of hydrogen produced by the electrolytic cell hydrogen production system and air, thereby realizing the conversion of hydrogen energy into the third electrical energy, and burning the remaining hydrogen exhaust gas and air exhaust gas in the electrochemical reaction to release heat and generate combustion heat.

[0063] For example, the fuel cell power generation system can generate third electrical energy through the electrochemical reaction of hydrogen and air, and introduce the remaining high-temperature hydrogen exhaust gas and air exhaust gas in the electrochemical reaction into the burner for catalytic combustion, and transfer the combustion heat generated by the combustion to the Carnot battery energy release cycle through the gas heat exchanger, and further use the waste heat of the gas to preheat the air and hydrogen at the inlet of the fuel cell power generation system, thereby realizing hydrogen energy power generation and waste heat utilization.

[0064] Among them, the Carnot battery energy release cycle system is used to use the cold energy stored in the Carnot battery energy storage cycle system to cool the first energy-releasing air and then compress it to obtain the third energy-releasing air, and use the combustion heat and the thermal energy stored in the Carnot battery energy storage cycle system to heat the fourth energy-releasing air twice to obtain the sixth energy-releasing air, and then use the sixth energy-releasing air to expand and do work to generate fourth electrical energy, so as to realize the conversion of combustion heat, thermal energy and cold energy into fourth electrical energy.

[0065] For example, the Carnot battery energy release cycle system can cool the first energy-releasing air through the low-temperature n-pentane medium stored in the cold storage low-temperature tank, reduce the compression power consumption, and obtain the low-temperature (for example, -45.81°C) second energy-releasing air after cooling, and then compress it to obtain the third energy-releasing air; and use the heat energy of the high-temperature molten salt medium stored in the heat storage high-temperature tank and the combustion heat in the gas heat exchanger to heat the fourth energy-releasing air to a high temperature (for example, 589.77°C) to obtain the sixth energy-releasing air, so that the sixth energy-releasing air expands to do work and generate electricity, thereby realizing the efficient conversion and output of heat energy and cold energy into electrical energy.

[0066] According to the embodiments of the present disclosure, the above-mentioned system realizes efficient coupling of physical energy storage and chemical energy storage through the coordinated work of electrolytic cells, fuel cells and Carnot batteries, can flexibly adjust the power and energy form of energy storage and energy release, meet the rapid response requirements of peak power, and provide long-term stable energy supply for user-side loads, which is suitable for long-term, efficient and flexible energy storage application scenarios of renewable energy. The system uses Carnot batteries, a large-scale long-term energy storage technology, as the basic load, and uses electrolytic cells and fuel cell technologies as control loads for source-load fluctuations to achieve rapid power consumption and supply, creating an efficient and flexible long-term energy storage system. Specifically, Carnot batteries store electrical energy in the form of heat energy and cold energy, and have long-term, large-scale energy storage capabilities; electrolytic cells store electrical energy in the form of hydrogen energy, and have long-term, fast-response energy storage capabilities. The above-mentioned system combines the characteristics of the two energy storage technologies, can effectively make up for the shortcomings of existing energy storage technologies, and better cope with the volatility of renewable energy and the changing needs of user loads.

[0067] This system combines the advantages of electrolytic cells, fuel cells and Carnot batteries. On the basis of realizing the efficient coupling of physical energy storage and chemical energy storage, the system utilizes the combustion heat of the high-temperature exhaust gas of the fuel cell power generation system to be transmitted to the Carnot battery energy release circulation system. Through the energy interaction between the two systems, the purpose of utilizing the combustion heat of the high-temperature exhaust gas of the fuel cell power generation system to improve the energy storage efficiency of the Carnot battery is achieved. Specifically, after the high-temperature exhaust gas of the fuel cell power generation system is further heated up by combustion, it is transmitted to the Carnot battery energy release circulation system to preheat the circulating air in the Carnot battery energy release circulation system so that the high-temperature air expands and does work to generate more electrical energy. Through the energy interaction and full utilization between the two systems, the system's dependence on external energy is reduced, and the overall energy efficiency is improved.

[0068] Figure 1 A system structure diagram of an electrolytic cell hydrogen production system and a Carnot battery energy storage cycle system in an energy storage stage according to an embodiment of the present invention is schematically shown; Figure 2 The system structure diagram of the fuel cell power generation system and the Carnot battery energy release cycle system in the energy release stage according to an embodiment of the present invention is schematically shown. Figure 1 , Figure 2 The system according to the embodiment of the present invention is further described.

[0069] like Figure 1 , Figure 2 As shown, the energy storage system includes an electrolytic cell hydrogen production system (A), a Carnot battery energy storage cycle system (B), a fuel cell power generation system (C), and a Carnot battery energy release cycle system (D).

[0070] Among them, Figure 1 As shown, in the energy storage stage, the electrolytic cell hydrogen production system (A) includes an electrolytic cell and a hydrogen tank, wherein the electrolytic cell can be a proton exchange membrane electrolytic cell (PEMEC) or an alkaline electrolytic cell (AEC). The electrolytic cell is used to use the first electrical energy to decompose water to generate hydrogen, and the hydrogen tank is used to store hydrogen.

[0071] Furthermore, the electrolytic cell hydrogen production system (A) may also include: a water storage tank, a water pump, and a separator.

[0072] like Figure 1As shown, in the energy storage stage, the Carnot battery energy storage cycle system (B) includes an energy storage compressor, an energy storage high-temperature heat exchanger, a heat storage high-temperature tank, a heat storage low-temperature tank, an energy storage regenerator, an energy storage expander, an energy storage low-temperature heat exchanger, a cold storage high-temperature tank, and a cold storage low-temperature tank, wherein the energy storage compressor is used to compress the second energy storage air using the second electric energy to form a high-temperature and high-pressure energy storage third air (for example, compressing the air from 280.00 ℃, 0.98 bar to 565.41 ℃, 3.72 bar), the energy storage high-temperature heat exchanger is used to heat the third energy storage air with the molten salt medium in the heat storage low-temperature tank, the molten salt medium is heated and stored in the heat storage high-temperature tank, and the third energy storage air forms a medium-temperature and high-pressure energy storage fourth air after heat exchange (for example, 300.00 ℃, 3.65 bar), the energy storage regenerator is used to exchange heat between the fourth energy storage air and the first energy storage air, the first energy storage air is heated to form the second energy storage air, and the fourth energy storage air is cooled to form the fifth energy storage air (for example, 52.74 ℃, 3.58 bar), the energy storage expander is used to use the fifth energy storage air to expand and do work to form the sixth energy storage air in a low-temperature state (for example, -55.81 ℃, 1.02 bar), the energy storage low-temperature heat exchanger is used to exchange heat between the sixth energy storage air and the n-pentane medium in the cold storage high-temperature tank, the n-pentane medium is cooled and stored in the cold storage low-temperature tank, and the sixth energy storage air is restored to normal temperature and pressure (for example, 25 ℃, 1.00 bar) after heat exchange, and is used as the first energy storage air for the next cycle.

[0073] The Carnot battery energy storage cycle system (B) realizes efficient conversion and storage of electrical energy into heat energy and cold energy through the reverse Brayton cycle. The circulating air in the system enters the energy storage compressor through the outlet of the energy storage low-temperature heat exchanger for compression. The compressed high-temperature and high-pressure air (e.g., 565.41 ℃, 3.72 bar) is heat-exchanged by the energy storage high-temperature heat exchanger, and the heat is stored in the molten salt medium in the heat storage tank. The high-pressure air then enters the energy storage expander to expand and work to form cold air (e.g., -55.81 ℃, 1.02 bar), and enters through the inlet of the energy storage low-temperature heat exchanger. The energy storage low-temperature heat exchanger exchanges the cold air's air cold energy and stores it in the n-pentane medium in the cold storage tank. The air that has undergone heat exchange passes through the outlet of the energy storage low-temperature heat exchanger for the next cycle.

[0074] like Figure 2 As shown, in the energy release stage, the fuel cell power generation system (C) includes a fuel cell and a burner, wherein the fuel cell is used for electrochemical reaction, and the burner is used for burning and releasing heat from the remaining hydrogen tail gas and air tail gas in the electrochemical reaction to generate combustion heat. Among them, the fuel cell can adopt a solid oxide fuel cell (SOFC). The combustion heat can be transmitted to the Carnot battery energy release cycle system (D), and the waste heat of the gas can be further used to preheat the air and hydrogen at the inlet of the fuel cell power generation system, so as to realize hydrogen power generation and waste heat utilization.

[0075] The fuel cell power generation system (C) may also include a hydrogen tank (equivalent to the hydrogen tank of the electrolytic cell hydrogen production system (A)), a hydrogen heat exchanger (such as hydrogen heat exchanger 2 in the figure), and a hydrogen expander. Electricity is generated through the high-temperature electrochemical reaction of hydrogen and air, and waste heat is recovered using the high-temperature tail gas.

[0076] like Figure 2 As shown, in the energy release stage, the Carnot battery energy release circulation system (D) includes an energy release low-temperature heat exchanger, the cold storage high-temperature tank, the cold storage low-temperature tank, an energy release compressor, an energy release high-temperature heat exchanger, the heat storage high-temperature tank, the heat storage low-temperature tank, a gas heat exchanger, an energy release expander, an energy release regenerator, and an energy release radiator, wherein the energy release low-temperature heat exchanger is used to exchange heat between the first energy release air and the n-pentane medium in the cold storage low-temperature tank, and the n-pentane medium enters the cold storage high-temperature tank after heating, and the first energy release air is cooled to produce the second energy release air (for example, from 35 ℃, 1.00 bar to -45.81 ℃, 0.98 bar), and the energy release compressor is used to compress the second energy release air to obtain the high-pressure energy release third air (for example, 112.70 ℃, 4.41bar), the energy-releasing high-temperature heat exchanger is used to exchange heat between the fourth energy-releasing air and the molten salt in the heat storage high-temperature tank, and the molten salt is cooled and enters the heat storage low-temperature tank. The fourth energy-releasing air is heated to form the fifth energy-releasing air (for example, 545.51 ℃, 4.23 bar), the gas heat exchanger is used to use the combustion heat to heat the fifth energy-releasing air to form the sixth energy-releasing air (for example, 589.77 ℃, 4.15 bar), the energy-releasing expander is used to use the sixth energy-releasing air to expand and do work to form the seventh energy-releasing air (for example, 304.17 ℃, 1.02 bar), the energy-releasing heat regenerator is used to exchange heat between the seventh energy-releasing air and the third energy-releasing air, and the third energy-releasing air is heated to form the fourth energy-releasing air, and the seventh energy-releasing air is cooled to form the eighth energy-releasing air (for example, 133.41 ℃, 1.00 bar), and the energy-releasing radiator is used to dissipate the heat of the eighth energy-releasing air to a normal temperature state (for example, 35 ℃, 1.00 bar), as the first energy-releasing air for the next cycle.

[0077] Among them, the high-temperature heat storage tank, the low-temperature heat storage tank, the high-temperature cold storage tank, and the low-temperature cold storage tank are equivalent to the high-temperature heat storage tank, the low-temperature heat storage tank, the high-temperature cold storage tank, and the low-temperature cold storage tank in the Carnot battery energy storage cycle system (B).

[0078] The Carnot battery energy release cycle system (D) achieves efficient conversion and release from heat and cold energy to electrical energy through a positive Brayton cycle. The circulating air in the system is cooled by the energy release low-temperature heat exchanger, and then compressed by the energy release compressor. The compressed air enters the energy release high-temperature heat exchanger to be heated, and then enters the gas heat exchanger to be heated to a high temperature by the gas, and enters the energy release expander to expand and generate electricity. The air at the expander outlet flows back into the energy release low-temperature heat exchanger, and the air that has undergone heat exchange passes through the outlet of the energy release low-temperature heat exchanger for the next cycle.

[0079] According to an embodiment of the present invention, Figure 2 As shown, the gas heat exchanger includes a first gas heat exchanger (gas heat exchanger 1) and a second gas heat exchanger (gas heat exchanger 2) connected in sequence to achieve cascade utilization of energy.

[0080] Specifically, the first part of the third energy-releasing air at the outlet of the energy-releasing compressor flows through the high-temperature energy-releasing heat exchanger to be heated once to form the fifth energy-releasing air, and then continues to flow through the first fuel gas heat exchanger to be heated twice to form the first part of the sixth energy-releasing air;

[0081] The second part of the energy-releasing third air at the outlet of the energy-releasing compressor flows through the second fuel gas heat exchanger to be heated to form the second part of the energy-releasing sixth air;

[0082] The heated first part of the energy-releasing sixth air and the second part of the energy-releasing sixth air together form the energy-releasing sixth air and enter the energy-releasing expander.

[0083] Furthermore, the specific connection relationship is:

[0084] The hot end inlet of the first gas heat exchanger is connected to the outlet of the burner, and the hot end outlet of the first gas heat exchanger is connected to the hot end inlet of the second gas heat exchanger;

[0085] The outlet of the energy-releasing compressor is directly or indirectly connected to the cold end inlet of the energy-releasing high-temperature heat exchanger, the cold end outlet of the energy-releasing high-temperature heat exchanger is connected to the cold end inlet of the first gas heat exchanger, and the cold end outlet of the first gas heat exchanger is connected to the inlet of the energy-releasing expander;

[0086] The outlet of the energy-releasing compressor is communicated with the cold-end inlet of the second gas heat exchanger, and the cold-end outlet of the second gas heat exchanger is communicated with the inlet of the energy-releasing expander.

[0087] According to an embodiment of the present invention, the Carnot battery energy release cycle system (D) introduces the hot air from the outlet of the energy release high-temperature heat exchanger into the gas heat exchanger 1, which is heated to a high temperature (for example, 589.77°C) by the gas, and then enters the energy release expander for expansion and power generation; at the same time, part of the medium-temperature air from the outlet of the energy release compressor is introduced into the gas heat exchanger 2 for secondary heat exchange with the gas, and the heated air is incorporated into the energy release expander for expansion and power generation, thereby realizing efficient cascade utilization of waste heat.

[0088] Furthermore, the Carnot battery energy release cycle system (D) draws out the heat in the heat storage tank to heat the normal temperature and high pressure (e.g. 45°C, 235.20 bar) hydrogen at the outlet of the hydrogen tank. The high temperature and high pressure (e.g. 545.41°C, 230.50 bar) hydrogen enters the expander to expand and generate electricity, and part of the compression work is recovered for power generation, thereby realizing efficient utilization of hydrogen energy and efficient thermal coupling in the energy release stage.

[0089] In the fuel cell power generation system (C), the SOFC high temperature tail gas (e.g. 850.00 ℃) contains some unused hydrogen. The tail gas is introduced into the combustion chamber for catalytic combustion, and the hydrogen is completely consumed to produce a higher temperature fuel gas (e.g. 1035.40 ℃). If this high temperature fuel gas is simply used to preheat the SOFC inlet air and hydrogen and then discharged to the environment, the waste heat of the high temperature fuel gas cannot be fully and effectively utilized.

[0090] To this end, a thermal coupling method of SOFC and Carnot battery is proposed to transfer the waste heat of SOFC tail gas to the Carnot battery system, increase the inlet temperature of the Carnot battery expander, and improve the system efficiency. In gas heat exchanger 1, SOFC tail gas transfers heat to the air. In gas heat exchanger 2, the temperature of SOFC tail gas further drops after heat exchange (for example, 550.85 ℃). At this time, SOFC tail gas is divided into two streams, which preheat the inlet air and hydrogen respectively, and then discharge the system. At this time, the exhaust temperature is low (for example, -3.23 ℃, 47.36 ℃), and the heat loss is reduced, which realizes the full utilization of the thermal energy of SOFC tail gas.

[0091] On the other hand, after the Carnot cell air is heated by the molten salt, it enters the gas heat exchanger 1 and is further heated by the SOFC tail gas, which makes up for the temperature loss caused by the heat exchange and has a higher working capacity. At the same time, in order to achieve cascade utilization of the SOFC tail gas, part of the air at the compressor outlet is drawn out and enters the gas heat exchanger 2. After the two gases merge, they enter the expander at a high temperature (for example, 589.63 ° C), which increases the work of the expander and improves the system efficiency.

[0092] According to an embodiment of the present invention, the fuel cell power generation system (C) also includes a preheater, which is used to preheat hydrogen and air using the combustion heat of the burner before the electrochemical reaction, and the inlet of the preheater is connected to the hot end outlet of the gas heat exchanger; specifically, the inlet of the preheater is connected to the hot end outlet of the second gas heat exchanger.

[0093] The preheater includes a first preheater (such as preheater 1 in the figure) and a second preheater (such as preheater 2 in the figure). The first preheater is used to preheat hydrogen before the electrochemical reaction, and the second preheater is used to preheat air before the electrochemical reaction.

[0094] According to an embodiment of the present invention, the high-temperature exhaust gas of the fuel cell power generation system (C) is further heated up by the burner, and then the waste heat is recovered in stages through two gas heat exchangers, thereby providing a heat source support for the Carnot battery energy release cycle. At the same time, the waste heat is used to preheat the inlet gas, thereby reducing the system's dependence on external energy and improving the overall energy efficiency.

[0095] According to an embodiment of the present invention, the Carnot battery energy release cycle system (D) also includes an energy release heat regenerator, which is used to use the waste heat of air expansion at the outlet of the energy release expander to preheat the energy release third air before entering the energy release high-temperature heat exchanger.

[0096] like Figure 2 As shown, the specific connection relationship is: the cold end inlet of the energy releasing heat regenerator is connected to the outlet of the energy releasing compressor, and the cold end outlet of the energy releasing heat regenerator is connected to the cold end inlet of the energy releasing high-temperature heat exchanger; the hot end inlet of the energy releasing heat regenerator is connected to the outlet of the energy releasing expander, and the hot end outlet of the energy releasing heat regenerator is connected to the hot end inlet of the energy releasing low-temperature heat exchanger.

[0097] According to an embodiment of the present invention, the waste heat of air expansion at the outlet of the energy releasing expander is used by the energy releasing heat regenerator to preheat the air before it enters the energy releasing high-temperature heat exchanger, thereby recovering the waste heat, reducing the system's dependence on external energy and improving the overall energy efficiency.

[0098] The following combination Figure 2 , the energy flow process of the embodiment of the present invention in the energy release cycle stage is exemplarily described.

[0099] like Figure 2 As shown, in the fuel cell power generation system (C), air and hydrogen are preheated (9-10, 11-13), respectively introduced into the SOFC anode and cathode, and electrochemical reactions occur to generate electrical energy (11-13, 12-14). The unreacted hydrogen and oxygen in the high-temperature exhaust gas of the electrochemical reaction enter the burner for catalytic combustion (14-15). The heat generated by the combustion is transferred to the Carnot battery energy release cycle (15-16, 16-17) through the gas heat exchanger. The waste heat of the gas is further used to preheat the air and hydrogen (19-21, 20-22), completing hydrogen energy power generation and waste heat utilization.

[0100] In the Carnot battery energy release cycle system (D), air is passed into the energy release low-temperature heat exchanger. After being cooled by the n-pentane fluid in the cold storage tank (1-2), the air is passed into the energy release compressor for compression (2-3). After being preheated by the energy release regenerator (3-4), the air enters the energy release high-temperature heat exchanger to be heated by the molten salt in the heat storage tank (4-5). Subsequently, the air enters the gas heat exchanger to be heated to a high temperature by the gas (5-6). The air enters the energy release expander to expand and generate electricity (6-7). The waste heat first enters the energy release regenerator to heat the outlet air of the energy release compressor (7-8), and then is discharged to the environment through the radiator (8-1), completing the conversion and release from heat energy and cold energy to electrical energy.

[0101] Among them, the Carnot battery energy release cycle system (D) introduces the hot air at the outlet of the energy release high-temperature heat exchanger into the gas heat exchanger 1, which is heated to a high temperature by the gas (5-6), and then enters the energy release expander for expansion and power generation (6-7); at the same time, part of the medium-temperature air (3x) at the outlet of the energy release compressor is introduced into the gas heat exchanger 2, and undergoes secondary heat exchange with the gas (17-18), and the heated air (6x) is incorporated into the energy release expander for expansion and power generation, thereby realizing efficient cascade utilization of waste heat.

[0102] Among them, the Carnot battery energy release circulation system (D) draws out part of the heat of the high-temperature molten salt in the heat storage tank to heat the high-pressure room-temperature hydrogen (11-12_0) at the outlet of the hydrogen tank. The high-temperature and high-pressure hydrogen enters the energy release expander to expand and generate electricity (12_0-12), and part of the compression work is recovered for power generation, realizing efficient utilization of hydrogen energy and efficient thermal coupling in the energy release stage.

[0103] Since the hydrogen and air for the electrochemical reaction in the fuel cell must be at normal pressure, in order to facilitate storage and reduce storage volume, the high-pressure hydrogen stored in the hydrogen tank must first be reduced to normal pressure. Figure 2 As shown, in the hydrogen heat exchanger 2, the high-temperature waste heat at the outlet of the heat storage tank is used to preheat the high-pressure and normal-temperature hydrogen flowing out of the hydrogen tank to obtain high-temperature and high-pressure hydrogen (in order to improve the expansion work efficiency), and then enters the hydrogen expander to generate power, and is reduced to normal-pressure hydrogen, which enters the fuel cell for electrochemical reaction, thereby realizing the recovery of part of the compression work for power generation, and further improving the energy utilization rate.

[0104] According to an embodiment of the present invention, an electrolytic cell hydrogen production system (A) generates hydrogen by electrolyzing water and stores it at high pressure, while using compression heat to recover waste heat.

[0105] like Figure 1As shown, the electrolytic cell hydrogen production system (A) also includes a hydrogen compressor and a hydrogen heat exchanger (such as hydrogen heat exchanger 1 in the figure), wherein the hydrogen compressor is used to compress the produced hydrogen to obtain compressed hydrogen, and the hydrogen heat exchanger is used to transfer the hydrogen compression heat generated during the hydrogen compression process to the Carnot battery energy storage cycle system (B). In order to facilitate storage and reduce storage volume, hydrogen needs to be compressed to high pressure for storage (for example, 240 bar), and compression heat will be generated during the compression process. In order to achieve efficient coupled utilization of energy, the hydrogen compression heat generated during the hydrogen compression process is transferred to the Carnot battery energy storage cycle system (B).

[0106] In the electrolytic cell hydrogen production system (A), the proton exchange membrane electrolyzer (PEMEC) or alkaline electrolyzer (AEC) decomposes water into hydrogen and oxygen through electrochemical action, inputs electrical energy, compresses the hydrogen to high pressure (e.g. 240 bar), and releases the compression heat to the Carnot battery energy storage cycle system (B). The cooled high-pressure hydrogen is stored in the hydrogen tank, completing the efficient conversion of electrical energy to hydrogen energy and the utilization of waste heat.

[0107] According to an embodiment of the present invention, the Carnot battery energy storage cycle system (B) is also used to: utilize the hydrogen compression heat introduced by the hydrogen heat exchanger to preheat the first part of the energy storage first air before entering the energy storage compressor.

[0108] like Figure 1 As shown, the Carnot battery energy storage cycle system (B) also includes an energy storage regenerator, which is used to: use the air compression waste heat at the outlet of the energy storage high-temperature heat exchanger to preheat the second part of the energy storage first air before entering the energy storage compressor.

[0109] That is, before entering the energy storage compressor, the air is divided into two streams, which are preheated by hydrogen heat exchanger 1 (using compression heat) and energy storage regenerator (using air compression waste heat at the outlet of energy storage high-temperature heat exchanger), and then enter the energy storage compressor for compression after preheating. If the air is directly compressed from normal temperature (e.g., 25°C) to high temperature (e.g., 565°C) without preheating, the pressure ratio is relatively large, the requirements for the compressor are relatively high, and the power consumption is relatively large. After preheating, the air is compressed from medium temperature (e.g., 280°C) to high temperature (e.g., 565°C), which can significantly reduce the pressure ratio, reduce compression power consumption, and reduce the technical difficulty of the compressor.

[0110] According to an embodiment of the present invention, the Carnot battery energy storage circulation system (B) draws out part of the air at room temperature (e.g., 25°C) at the outlet of the energy storage low-temperature heat exchanger to absorb the compression heat of hydrogen, and the heated air is incorporated into the compressor to achieve efficient utilization of the system's waste heat.

[0111] According to an embodiment of the present invention, in order to achieve the above object, Figure 1As shown, the system connection relationship is: the outlet of the energy storage low-temperature heat exchanger is connected to the cold end inlet of the hydrogen heat exchanger, and the cold end outlet of the hydrogen heat exchanger is connected to the inlet of the energy storage compressor; the outlet of the energy storage low-temperature heat exchanger is connected to the cold end inlet of the energy storage regenerator, and the cold end outlet of the energy storage regenerator is connected to the inlet of the energy storage compressor; the hot end outlet of the energy storage high-temperature heat exchanger is connected to the hot end inlet of the energy storage regenerator, and the hot end outlet of the energy storage regenerator is connected to the inlet of the energy storage expander.

[0112] The Carnot battery energy storage cycle system (B) realizes efficient conversion and storage of electrical energy into heat energy and cold energy through the reverse Brayton cycle. The circulating air in the system enters the energy storage compressor through the outlet of the energy storage low-temperature heat exchanger for compression. The compressed high-temperature and high-pressure air (e.g., 565.41 °C, 3.72 bar) passes through the energy storage high-temperature heat exchanger for heat exchange, and the heat is stored in the molten salt medium in the heat storage tank. The high-pressure air (e.g., 3.58 bar) then enters the energy storage expander to expand and work to form cold air (e.g., -55.81 °C), which enters through the inlet of the energy storage low-temperature heat exchanger. The energy storage low-temperature heat exchanger exchanges the cold air's air cold energy and stores it in the n-pentane medium in the cold storage tank. The air that has undergone heat exchange passes through the outlet of the energy storage low-temperature heat exchanger for the next cycle.

[0113] The following combination Figure 1 , the energy flow process of the embodiment of the present invention in the energy storage cycle stage is exemplarily described.

[0114] like Figure 1 As shown, in the electrolytic cell hydrogen production system (A), the proton exchange membrane electrolyzer (PEMEC) or alkaline electrolyzer (AEC) decomposes water into hydrogen and oxygen through electrochemical action, inputs electrical energy, compresses the hydrogen to high pressure (7-8), and releases the compression heat to the Carnot battery energy storage cycle system (B) (8-9). The cooled high-pressure hydrogen is stored in the hydrogen tank, completing the efficient conversion of electrical energy to hydrogen energy and the utilization of waste heat;

[0115] Among them, the Carnot battery energy storage cycle system (B) compresses the air to a high temperature and high pressure state (2-3) through a reverse Brayton cycle, and stores the heat energy in the molten salt fluid in the heat storage tank after heat exchange (3-4). The air then enters the energy storage regenerator, and the excess heat is used to preheat the air at the inlet of the energy storage compressor (4-5). The air is then cooled by cooling water (5-5x), expanded to a low temperature and normal pressure state (5x-6), and heat is exchanged with the n-pentane fluid in the cold storage tank to store cold energy (6-1), completing the conversion and storage from electrical energy to thermal energy and cold energy.

[0116] Among them, the Carnot battery energy storage circulation system (B) draws out part of the normal temperature air (1x) at the outlet of the energy storage low-temperature heat exchanger to absorb the hydrogen compression heat (7-8), and the heated air (2x) is introduced into the compressor to achieve efficient utilization of the waste heat of system A.

[0117] According to the embodiment of the present invention, it can be seen from the above description that the system realizes multi-stage thermal coupling of energy storage and energy release stages to improve the overall energy efficiency. In the electrolytic cell hydrogen production system, the waste heat generated during the hydrogen compression process is used to heat the air at room temperature (e.g., 25°C) in the Carnot battery energy storage stage, thereby improving the energy storage efficiency; at the same time, part of the high-temperature heat storage molten salt in the Carnot battery energy release stage heats the high-pressure hydrogen (e.g., 235.20 bar) in the SOFC power generation system through the hydrogen heat exchanger 2, so that it expands and works under high temperature and high pressure (e.g., 545.41°C, 230.50 bar), thereby recovering part of the energy required for hydrogen compression. This multi-stage thermal coupling design realizes flexible and efficient use of heat in the system, significantly improving energy utilization and energy storage efficiency.

[0118] Furthermore, the high-temperature waste heat of the exhaust gas at the SOFC outlet is utilized through the gas heat exchanger 1 and the gas heat exchanger 2, and the waste heat is transferred to the Carnot battery energy release cycle system (D), which effectively improves the efficiency of the Carnot battery.

[0119] Table 1 shows an example of Figure 1 Thermodynamic parameters of the main thermal nodes in the energy storage cycle stage are shown.

[0120] Table 1

[0121]

[0122] Among them, Th,h is the node parameter of the cold end outlet of the energy releasing high-temperature heat exchanger (heat storage high-temperature tank inlet) (temperature of the molten salt after being heated), Th,l is the node parameter of the cold end inlet of the energy releasing high-temperature heat exchanger (heat storage low-temperature tank outlet) (temperature before the molten salt is heated), Tc,h is the node parameter of the hot end inlet of the energy releasing low-temperature heat exchanger (cold storage high-temperature tank outlet) (temperature before n-pentane is cooled), and Tc,l is the node parameter of the hot end outlet of the energy releasing low-temperature heat exchanger (cold storage low-temperature inlet) (temperature after n-pentane is cooled).

[0123] Table 2 shows an example of Figure 2 Thermodynamic parameters of the main thermodynamic nodes during the energy release cycle are shown.

[0124] Table 2

[0125]

[0126] Among them, Th,h is the node parameter of the hot end inlet of the energy releasing high-temperature heat exchanger (outlet of the heat storage high-temperature tank) (temperature before the molten salt releases heat energy), Th,l is the node parameter of the hot end outlet of the energy releasing high-temperature heat exchanger (inlet of the heat storage low-temperature tank) (temperature after the molten salt releases heat energy), Tc,h is the node parameter of the cold end outlet of the energy releasing low-temperature heat exchanger (inlet of the cold storage high-temperature tank) (temperature after n-pentane releases cold energy), and Tc,l is the node parameter of the cold end inlet of the energy releasing low-temperature heat exchanger (outlet of the cold storage low-temperature tank) (temperature before n-pentane releases cold energy).

[0127] As shown in Table 1 and Table 2, in the fuel cell power generation system (C), SOFC operates at a high temperature of 850°C (points 14 and 15), and its high-temperature tail gas contains some unused hydrogen. The tail gas is introduced into the combustion chamber for catalytic combustion, and the hydrogen is completely consumed to produce a higher temperature fuel gas (point 16, 1035.40°C). If this high-temperature fuel gas is simply used to preheat the SOFC inlet air and hydrogen (points 10 and 13, 530.85°C) and then discharged to the environment, the waste heat of the high-temperature fuel gas cannot be fully and effectively utilized.

[0128] On the other hand, due to the irreversible loss of the heat exchange process, the Carnot battery causes the maximum temperature of the air in the energy release stage to be lower than the maximum temperature in the energy storage stage, resulting in a decrease in work capacity and a decrease in cycle efficiency. In the energy storage stage, the high-temperature air at the outlet of the energy storage compressor (3 points, 565.41°C) stores heat energy in the molten salt and heats it to 555.41°C; in the energy release stage, the air at the outlet of the energy release regenerator can only reach 545.41°C (12 points) after being heated by the high-temperature molten salt. The temperature loss of the two heat exchanges causes the temperature of the air to drop when it enters the energy release expander, and the work capacity is reduced.

[0129] To this end, a thermal coupling method between SOFC and Carnot battery is proposed to transfer the waste heat of SOFC tail gas to the Carnot battery energy release circulation system (D), increase the inlet temperature of the Carnot battery energy release expander, and improve the system efficiency. In gas heat exchanger 1, SOFC tail gas transfers heat to the air, and the temperature drops to 565.41℃ (point 17); in gas heat exchanger 2, after the SOFC tail gas is heat exchanged, the temperature further drops to 550.85℃ (point 18). At this time, the SOFC tail gas is divided into two streams, which preheat the inlet air and hydrogen respectively, and then discharge the system. At this time, the exhaust heat temperatures are -3.23℃ (point 21) and 47.36℃ (point 22), which are close to or lower than the ambient temperature. The heat loss is greatly reduced, and the full utilization of the heat energy of SOFC tail gas is achieved.

[0130] On the other hand, in the Carnot battery energy release cycle system (D), the air is heated by the molten salt (point 5), enters the gas heat exchanger 1 and is further heated to 589.77°C by the SOFC tail gas (point 6), which makes up for the temperature loss caused by heat exchange and has a higher work capacity; at the same time, in order to achieve cascade utilization of SOFC tail gas, part of the air at the outlet of the energy release compressor is drawn out (point 3x), enters the gas heat exchanger 2, and is heated to 545.41°C (point 6x). After the two gases merge (point 6mix), they enter the energy release expander at a high temperature of 589.63°C, increasing the work of the expander and improving the system efficiency.

[0131] In addition, in the energy storage stage, in order to achieve high-density and safe storage of hydrogen, the hydrogen is compressed to 240 bar and cooled to 45°C for storage. In the energy release stage, since the working pressure of SOFC is normal pressure, the high-pressure hydrogen in the storage tank needs to be depressurized and introduced into SOFC. If the hydrogen is directly throttled and depressurized, the energy contained in the high-pressure hydrogen cannot be recovered. At this time, through the thermal coupling method of the two systems, part of the high-temperature molten salt in the heat storage stage of the Carnot battery is drawn out and enters the hydrogen heat exchanger 2, and the hydrogen is heated to 545.41°C (point 12). The cooled molten salt returns to the low-temperature storage tank for storage, waiting for the heat storage process of the next energy storage cycle. The high-temperature and high-pressure hydrogen enters the hydrogen expander to expand and do work, recovering part of the hydrogen energy and improving the overall efficiency of the system.

[0132] Figure 3 The diagram schematically shows an energy flow diagram between systems according to an embodiment of the present invention.

[0133] from Figure 3 It can be seen that the electrolytic cell hydrogen production system (PEMEC hydrogen production is taken as an example here) efficiently converts electrical energy (10307kw) into hydrogen energy (7500kw), and at the same time recovers the hydrogen compression heat energy (332kw) and supplies it to the Carnot battery energy storage cycle; the Carnot battery energy storage cycle efficiently converts electrical energy (11300kw) into cold energy (4065kw) and heat energy (14295kw), and supplies part of the molten salt heat energy to the SOFC for heating the SOFC high-pressure hydrogen to expand and do work under high temperature and high pressure conditions; the SOFC power generation system efficiently converts hydrogen energy into electrical energy (3750kw), and effectively recovers the waste heat of SOFC tail gas (2523kw) and inputs it into the Carnot battery energy release cycle to increase the expander inlet temperature and improve the cycle efficiency; the Carnot battery energy release cycle efficiently converts the heat energy, cold energy and waste heat of the SOFC system in the energy storage cycle into electrical energy.

[0134] The system achieves efficient conversion between electrical energy and thermal energy, cold energy and hydrogen energy through the coordinated work of electrolytic cells, fuel cells and Carnot batteries. It can flexibly adjust the power and energy form of energy storage and release to meet the rapid response needs of peak power and provide large-scale, long-term and stable energy supply for user-side loads. It is suitable for long-term, efficient and flexible energy storage application scenarios of renewable energy.

[0135] In order to illustrate the technical effect of the energy storage system according to the embodiment of the present invention, experimental data comparison is performed between the energy storage system according to the embodiment of the present invention and other energy storage systems (named as reference systems).

[0136] Reference system, including Figure 1 , Figure 2 The similar electrolytic cell hydrogen production system (A), Carnot battery energy storage cycle system (B), fuel cell power generation system (C), and Carnot battery energy release cycle system (D) are different in that there is no exchange of hydrogen compression heat between the electrolytic cell hydrogen production system (A) and the Carnot battery energy storage cycle system (B), and there is no heat exchange of the residual exhaust combustion heat of the electrochemical reaction between the fuel cell power generation system (C) and the Carnot battery energy release cycle system (D), and there is no heat exchange between the molten salt and the high-pressure hydrogen in the heat storage tank. That is, the electrolytic cell-fuel cell hydrogen energy storage system and the Carnot battery energy storage system in this reference system are independent and do not exchange heat. The two energy storage systems are compared, and the system parameters are shown in Table 3.

[0137] Table 3

[0138]

[0139] It can be seen from Table 3 that for the reference system, in the energy storage stage, the maximum temperature of the Carnot battery cycle is 565.41°C, that is, the maximum temperature of the air after being compressed by the energy storage compressor is 565.41°C; but due to the two heat exchange processes from air to molten salt and from molten salt to air, in the energy release stage, for a single Carnot battery system, the maximum cycle temperature is only 545.41°C, that is, the temperature of the air after absorbing heat is only 545.41°C, there is some heat loss, the work done in the energy release stage is 6383.13 kW, and the round-trip efficiency (that is, the ratio of the work done in the energy release stage to the power consumed in the energy storage stage) is 56.49%.

[0140] As for the system of the embodiment of the present invention, in the energy release stage of the Carnot battery, the air absorbs heat and enters the gas heat exchanger 1, and continues to be heated to 589.63°C, which effectively compensates for the heat loss in the heat exchange stage. The work done in the energy release stage is 7463.25 kW, and the round-trip efficiency is 66.05%, which is greatly improved compared with the single Carnot battery energy storage system. It proves that the coupling system proposed in the present invention can effectively utilize the waste heat at the SOFC outlet, improve the round-trip efficiency of the Carnot battery, and improve the overall energy efficiency.

[0141] At the same time, it can be seen from Table 3 that in the system of the embodiment of the present invention, the imported hydrogen of the SOFC power generation system (C) absorbs the heat of the high-temperature molten salt stored in the Carnot battery, reaches a high temperature and high pressure state, and then expands to do work, which increases the power generation of the system by 538.53 kW, and increases the round-trip efficiency of the hydrogen energy storage system from 36.38% to 41.61%, and the round-trip efficiency of the total system from 46.90% to 54.39%, which proves that the system of the embodiment of the present invention can achieve efficient coupling of the hydrogen energy storage system and the Carnot battery system, and comprehensively improve the energy efficiency of the system.

[0142] Based on the above energy storage system, another aspect of the present invention provides an energy storage method.

[0143] Figure 4 The operation flow chart of the energy storage method according to an embodiment of the present invention is schematically shown.

[0144] like Figure 4 As shown, the method includes operations S1 to S4.

[0145] In operation S1, first electrical energy is used to decompose water to generate hydrogen, so as to convert the first electrical energy into hydrogen energy and store it;

[0146] In operation S2, the second electric energy is used to compress the second energy storage air to form the third energy storage air, the air heat energy of the third energy storage air is heat exchanged and stored to form the fourth energy storage air, and the fifth energy storage air is used to expand and do work to form the sixth energy storage air in a low temperature state, and the air cold energy of the sixth energy storage air is heat exchanged and stored, so as to convert the second electric energy into heat energy and cold energy and store them;

[0147] In operation S3, the third electric energy is generated by the electrochemical reaction of the stored hydrogen and the air, so as to realize the conversion of the hydrogen energy into the third electric energy, and the remaining hydrogen tail gas and the air tail gas in the electrochemical reaction are burned to release heat, thereby generating combustion heat;

[0148] In operation S4, the first energy-releasing air is cooled by utilizing the stored cold energy and then compressed to obtain the third energy-releasing air. The fourth energy-releasing air is heated twice by utilizing the combustion heat and the stored thermal energy to obtain the sixth energy-releasing air. The sixth energy-releasing air is expanded to do work to generate the fourth electrical energy, thereby realizing the conversion of the combustion heat, thermal energy and cold energy into the fourth electrical energy.

[0149] For the specific implementation methods of the above operations S1 to S4, reference may be made to the description of the energy storage system in the above embodiments, which will not be repeated here.

[0150] According to the embodiments of the present disclosure, the above method can realize the efficient coupling of physical energy storage and chemical energy storage, can flexibly adjust the power and energy form of energy storage and energy release, meet the rapid response requirements of peak power, and provide long-term stable energy supply for user-side loads, which is suitable for long-term, efficient and flexible energy storage application scenarios of renewable energy. In view of the volatility of renewable energy generation and the peak load requirements of users, electrolytic cell and fuel cell technology are used to achieve rapid power consumption and supply, and create an efficient and flexible coupled energy storage system. Carnot batteries store electrical energy in the form of heat energy and cold energy, and have long-term, large-scale energy storage capabilities; electrolytic cells and fuel cells store electrical energy in the form of hydrogen energy, and have long-term, fast-response energy storage capabilities. The above method combines the characteristics of the two energy storage technologies, can effectively make up for the shortcomings of existing energy storage technologies, and better cope with the volatility of renewable energy and the changing needs of user loads.

[0151] The embodiments of the present invention are described above. However, these embodiments are only for the purpose of illustration, and are not intended to limit the scope of the present invention. Although each embodiment is described above, it does not mean that the measures in each embodiment cannot be used in combination advantageously. Without departing from the scope of the present invention, those skilled in the art may make various substitutions and modifications, which should all fall within the scope of the present invention.

Claims

1. A physical and chemical coupled high-efficiency long-term energy storage system, characterized in that: include: An electrolytic cell hydrogen production system, used to utilize the first electrical energy to decompose water to generate hydrogen, so as to realize the conversion of the first electrical energy into hydrogen energy, and store the hydrogen; The Carnot battery energy storage cycle system is used to compress the first energy storage air with the second electric energy to form the second energy storage air, and to store the air heat energy of the second energy storage air in the molten salt medium of the heat storage tank to form the third energy storage air, and to expand the third energy storage air to form cold air, and to store the air cold energy of the cold air in the normal pentane medium of the cold storage tank to convert the second electric energy into heat energy and cold energy for storage; A fuel cell power generation system, used to generate a third electric energy by an electrochemical reaction between the hydrogen produced by the electrolytic cell hydrogen production system and air, realize the conversion of hydrogen energy into the third electric energy, and burn the remaining hydrogen tail gas and air tail gas in the electrochemical reaction to release heat and generate combustion heat; The Kanot battery energy release cycle system is used to utilize the cold energy stored in the Kanot battery energy storage cycle system to cool the first energy-releasing air, and then compress it to obtain the second energy-releasing air, and utilize the combustion heat and the thermal energy stored in the Kanot battery energy storage cycle system to heat the third energy-releasing air to obtain the fourth energy-releasing air, and then utilize the fourth energy-releasing air to expand and do work to generate fourth electrical energy, so as to realize the conversion of combustion heat, thermal energy and cold energy into fourth electrical energy.

2. The system according to claim 1, characterized in that: The electrolytic cell hydrogen production system comprises an electrolytic cell and a hydrogen tank, wherein the electrolytic cell is used to decompose water to generate hydrogen using the first electrical energy, and the hydrogen tank is used to store the hydrogen; The Carnot battery energy storage cycle system includes an energy storage compressor, an energy storage high-temperature heat exchanger, a heat storage high-temperature tank, a heat storage low-temperature tank, an energy storage regenerator, an energy storage expander, an energy storage low-temperature heat exchanger, a cold storage high-temperature tank, and a cold storage low-temperature tank, wherein the energy storage compressor is used to compress the second energy storage air using the second electric energy to form the third energy storage air, and the energy storage high-temperature heat exchanger is used to exchange heat between the third energy storage air and the molten salt medium in the heat storage low-temperature tank, and the molten salt medium is heated and stored in the heat storage high-temperature tank, and the third energy storage air is heat exchanged to form the fourth energy storage air. The energy storage regenerator is used to exchange heat between the fourth energy storage air and the first energy storage air. The first energy storage air is heated to form the second energy storage air. The fourth energy storage air is cooled to form the fifth energy storage air. The energy storage expander is used to expand the fifth energy storage air to form the sixth energy storage air. The energy storage low-temperature heat exchanger is used to exchange heat between the sixth energy storage air and the n-pentane medium in the cold storage high-temperature tank. The n-pentane medium is cooled and stored in the cold storage low-temperature tank. After the heat exchange, the sixth energy storage air is restored to the temperature and pressure state of the first energy storage air for the next cycle. The fuel cell power generation system comprises a fuel cell and a burner, wherein the fuel cell is used for the electrochemical reaction, and the burner is used for burning the remaining hydrogen tail gas and air tail gas in the electrochemical reaction to release heat and generate combustion heat; The Carnot battery energy release circulation system includes an energy-releasing low-temperature heat exchanger, the cold storage high-temperature tank, the cold storage low-temperature tank, an energy-releasing compressor, an energy-releasing high-temperature heat exchanger, the heat storage high-temperature tank, the heat storage low-temperature tank, a gas heat exchanger, an energy-releasing expander, an energy-releasing heat regenerator, and an energy-releasing radiator, wherein the energy-releasing low-temperature heat exchanger is used to exchange heat between the first energy-releasing air and the n-pentane medium in the cold storage low-temperature tank, and the n-pentane medium enters the cold storage high-temperature tank after heating, and the first energy-releasing air is cooled to produce the second energy-releasing air, and the energy-releasing compressor is used to compress the second energy-releasing air to obtain the third energy-releasing air, and the energy-releasing high-temperature heat exchanger is used to exchange heat between the fourth energy-releasing air and the heat storage high-temperature tank. The molten salt in the warm tank is used for heat exchange, and the molten salt enters the heat storage low-temperature tank after cooling down. The fourth energy-releasing air is heated to form the fifth energy-releasing air. The gas heat exchanger is used to use the combustion heat to heat the fifth energy-releasing air to form the sixth energy-releasing air. The energy-releasing expander is used to use the sixth energy-releasing air to expand and do work to form the seventh energy-releasing air. The energy-releasing heat regenerator is used to exchange heat between the seventh energy-releasing air and the third energy-releasing air. The third energy-releasing air is heated to form the fourth energy-releasing air. The seventh energy-releasing air is cooled to form the eighth energy-releasing air. The energy-releasing radiator is used to dissipate the heat of the eighth energy-releasing air to the temperature state of the first air for the next cycle. The electrolytic cell adopts a proton exchange membrane electrolytic cell or an alkaline electrolytic cell; The fuel cell is a solid oxide fuel cell.

3. The system according to claim 2, characterized in that: The gas heat exchanger comprises a first gas heat exchanger and a second gas heat exchanger connected in sequence; The first part of the third energy-releasing air at the outlet of the energy-releasing compressor flows through the high-temperature energy-releasing heat exchanger to be heated once to form the fifth energy-releasing air, and continues to flow through the first fuel gas heat exchanger to be heated twice to form the first part of the sixth energy-releasing air; The second part of the energy-releasing third air at the outlet of the energy-releasing compressor flows through the second fuel gas heat exchanger to be heated to form the second part of the energy-releasing sixth air; The heated first part of the energy-releasing sixth air and the second part of the energy-releasing sixth air together form the energy-releasing sixth air and enter the energy-releasing expander.

4. The system according to claim 3, characterized in that: The hot end inlet of the first gas heat exchanger is communicated with the outlet of the burner, and the hot end outlet of the first gas heat exchanger is communicated with the hot end inlet of the second gas heat exchanger; The outlet of the energy-releasing compressor is directly or indirectly connected to the cold-end inlet of the energy-releasing high-temperature heat exchanger, the cold-end outlet of the energy-releasing high-temperature heat exchanger is connected to the cold-end inlet of the first gas heat exchanger, and the cold-end outlet of the first gas heat exchanger is connected to the inlet of the energy-releasing expander; The outlet of the energy-releasing compressor is communicated with the cold-end inlet of the second gas heat exchanger, and the cold-end outlet of the second gas heat exchanger is communicated with the inlet of the energy-releasing expander.

5. The system according to claim 2, characterized in that: The fuel cell power generation system further comprises a preheater, which is used to preheat the hydrogen and the air by using the combustion heat of the burner before the electrochemical reaction, and the inlet of the preheater is connected to the hot end outlet of the gas heat exchanger; Wherein, the preheater includes a first preheater and a second preheater, the first preheater is used to preheat the hydrogen before the electrochemical reaction, and the second preheater is used to preheat the air before the electrochemical reaction.

6. The system according to claim 2, characterized in that: The energy-releasing heat regenerator is used to utilize the residual heat of air expansion at the outlet of the energy-releasing expander to preheat the energy-releasing third air before entering the energy-releasing high-temperature heat exchanger; The cold end inlet of the energy releasing heat regenerator is communicated with the outlet of the energy releasing compressor, and the cold end outlet of the energy releasing heat regenerator is communicated with the cold end inlet of the energy releasing high temperature heat exchanger; The hot end inlet of the energy releasing heat regenerator is communicated with the outlet of the energy releasing expander, and the hot end outlet of the energy releasing heat regenerator is communicated with the hot end inlet of the energy releasing low-temperature heat exchanger.

7. The system according to claim 2, characterized in that: The electrolytic cell hydrogen production system also includes a hydrogen compressor and a hydrogen heat exchanger, wherein the hydrogen compressor is used to compress the produced hydrogen to obtain compressed hydrogen, and the hydrogen heat exchanger is used to transfer the hydrogen compression heat generated during the hydrogen compression process to the Carnot battery energy storage cycle system.

8. The system according to claim 7, characterized in that: The Carnot battery energy storage cycle system is also used to: use the hydrogen compression heat introduced by the hydrogen heat exchanger to preheat the first part of the energy storage first air before entering the energy storage compressor; The energy storage regenerator is used to preheat the second part of the energy storage first air before entering the energy storage compressor by utilizing the residual heat of air compression at the outlet of the energy storage high-temperature heat exchanger.

9. The system according to claim 8, characterized in that: The outlet of the energy storage low-temperature heat exchanger is connected to the cold end inlet of the hydrogen heat exchanger, and the cold end outlet of the hydrogen heat exchanger is connected to the inlet of the energy storage compressor; The outlet of the energy storage low-temperature heat exchanger is communicated with the cold end inlet of the energy storage regenerator, and the cold end outlet of the energy storage regenerator is communicated with the inlet of the energy storage compressor; The hot end outlet of the energy storage high temperature heat exchanger is communicated with the hot end inlet of the energy storage regenerator, and the hot end outlet of the energy storage regenerator is communicated with the inlet of the energy storage expander.

10. An energy storage method using the energy storage system according to any one of claims 1 to 9, characterized in that: include: Decomposing water to generate hydrogen using the first electrical energy, so as to convert the first electrical energy into hydrogen energy for storage; The second electric energy is used to compress the second energy storage air to form the third energy storage air, the air heat energy of the third energy storage air is heat exchanged and stored to form the fourth energy storage air, and the fifth energy storage air is used to expand and do work to form the sixth energy storage air, and the air cold energy of the sixth energy storage air is heat exchanged and stored, so as to convert the second electric energy into heat energy and cold energy for storage; The electrochemical reaction of the hydrogen and the air is used to generate the third electric energy, so as to realize the conversion of the hydrogen energy into the third electric energy, and the remaining hydrogen tail gas and the air tail gas in the electrochemical reaction are burned to release heat, so as to generate combustion heat; The first energy-releasing air is cooled by the cold energy and then compressed to obtain the second energy-releasing air. The fourth energy-releasing air is heated twice by the combustion heat and the thermal energy to obtain the sixth energy-releasing air. The sixth energy-releasing air is then expanded and used to do work to generate the fourth electrical energy, so as to realize the conversion of the combustion heat, thermal energy and cold energy into the fourth electrical energy.

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