Supercritical carbon dioxide coupling fused salt double-source energy storage system and method

Abstract

The invention provides a supercritical carbon dioxide coupling fused salt double-source energy storage system and method.In the system, the output end of a low-temperature mixture storage tank is connected with the input end of a heating system, the output end of the heating system is connected with the input end of a high-temperature mixture storage tank, and the output end of the high-temperature mixture storage tank is connected with the input end of a gas-liquid separator; the gas output end of the gas-liquid separator is connected with the first input end of the power generation system, the fused salt output end of the gas-liquid separator is connected with the fused salt input end of the heat exchanger, the fused salt output end of the heat exchanger is connected with the fused salt input end of the low-temperature mixture storage tank, and the first output end of the power generation system is connected with the gas input end of the heat exchanger. The gas output end of the heat exchanger is connected with the second input end of the power generation system, and the second output end of the power generation system is connected with the gas input end of the low-temperature mixture storage tank. According to the scheme, the viscosity of a molten salt system is reduced and the fluidity is improved by utilizing the solvation effect of supercritical carbon dioxide, and the utilization and conversion efficiency of energy is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of molten salt energy storage, and in particular to a supercritical carbon dioxide coupled molten salt dual-source energy storage system and method. Background Art

[0002] As the world gradually relies on renewable energy, energy storage technology plays an increasingly important role in balancing energy supply and demand and improving energy efficiency. As a medium- and high-temperature heat transfer and heat storage medium, molten salt has the advantages of excellent high-temperature stability, large specific heat capacity, low viscosity, and low saturated vapor pressure compared to conventional heat transfer media. It can effectively store thermal energy and release it when needed. The molten salt energy storage system has the advantages of high energy storage density, excellent thermal utilization efficiency, green environmental protection, good thermal stability and economy. It is currently the first choice for large-scale, medium- and long-term high-temperature heat storage technology. It has shown broad application prospects in many fields such as solar thermal power generation, industrial waste heat utilization, and clean heating.

[0003] In the molten salt heat storage system, the viscosity of the molten salt is a key performance parameter. Viscosity affects the fluidity of the molten salt, thereby affecting the pumping capacity and the operating efficiency of the entire system. However, in the existing molten salt heat storage technology, the viscosity of common molten salts (such as solar salt, the main components are 60% NaNO3, 40% KNO3; Hitec salt, the main components are 40% NaNO2 + 7% NaNO3 + 53% KNO3) will increase significantly when the temperature drops. This phenomenon is particularly obvious in low-temperature areas, resulting in a decrease in the fluidity of the molten salt, which not only increases the difficulty of pumping, but may even cause the molten salt system to solidify, resulting in "freezing and blocking", damaging the system equipment, and seriously affecting the safety of the energy storage system. In response to this problem, the patents CN105567176A, CN105199678A, CN10538540A and CN105400498A disclose multi-element low-melting point mixed molten salts by modifying the molten salt material. Although these molten salts have a low melting point, these formulas all contain Ca(NO3)2, which is very easy to absorb water and has poor high-temperature thermal stability, which can easily deteriorate the fluidity of the molten salt system and cause local high temperature deterioration, which may damage system components. Public patents CN106131986A, CN117703742A, CN117870431A and CN115614715A heat the molten salt in the low-temperature zone by equipping it with electric heating and other equipment to keep it above the melting point to avoid solidification. However, this technical solution will increase energy consumption and the cost of system operation. The continuous operation of the electric heater may cause aging of components, increase failure rates and other safety accidents.

[0004] At the same time, molten salt, as a heat storage medium, needs to be exchanged through a heat exchanger during the energy storage and release process. The thermal conductivity of commonly used molten salts is generally low, which limits the speed and efficiency of heat transfer. In actual operation, the molten salt heat storage system is prone to temperature stratification, resulting in reduced heat storage and release efficiency, which in turn causes the problem of low efficiency of the power generation system, which also needs to be solved urgently. Summary of the invention

[0005] In order to overcome the deficiencies of the above-mentioned prior art, the method of the present invention provides a supercritical carbon dioxide coupled molten salt dual-source energy storage system and method, which can effectively utilize the solvation effect of supercritical carbon dioxide to reduce the viscosity of the molten salt system and increase the fluidity, and efficiently convert thermal energy into electrical energy through the supercritical carbon dioxide Brayton cycle, thereby improving the utilization and conversion efficiency of energy, so as to solve the problems of excessive viscosity of molten salt in the low temperature zone and low thermal conductivity of molten salt in the prior art.

[0006] The present invention provides a supercritical carbon dioxide coupled molten salt dual-source energy storage system, comprising a low-temperature mixture storage tank, a heating system, a high-temperature mixture storage tank, a gas-liquid separator, a heat exchanger and a power generation system; The mixture output end of the low-temperature mixture storage tank is connected to the mixture input end of the heating system, the mixture output end of the heating system is connected to the mixture input end of the high-temperature mixture storage tank, the mixture output end of the high-temperature mixture storage tank is connected to the mixture input end of the gas-liquid separator, the gas-liquid separator is used to separate the mixture into supercritical carbon dioxide and molten salt, the gas output end of the gas-liquid separator is connected to the first gas input end of the power generation system, the molten salt output end of the gas-liquid separator is connected to the molten salt input end of the heat exchanger, the molten salt output end of the heat exchanger is connected to the molten salt input end of the low-temperature mixture storage tank, the first gas output end of the power generation system is connected to the gas input end of the heat exchanger, the gas output end of the heat exchanger is connected to the second gas input end of the power generation system, and the second gas output end of the power generation system is connected to the gas input end of the low-temperature mixture storage tank.

[0007] Further, it also includes a first high-pressure compressor; The first gas output end of the power generation system is connected to the gas input end of the first high-pressure compressor, and the gas output end of the first high-pressure compressor is connected to the gas input end of the heat exchanger.

[0008] Further, it also includes a second high-pressure compressor; The second gas output end of the power generation system is connected to the gas input end of the second high-pressure compressor, and the gas output end of the second high-pressure compressor is connected to the gas input end of the low-temperature mixture storage tank.

[0009] Furthermore, the heating system uses at least one of a high temperature heater, a concentrating solar collector tower, a trough collector, a dish collector, a trough collector, a linear Fresnel collector, an industrial waste heat collector, and an industrial steam heat exchanger.

[0010] Furthermore, the molten salt is selected from any one of solar salt, Hitec salt, Hitec XL salt, chloride salt and carbonate salt.

[0011] Furthermore, the power generation system adopts a turbine.

[0012] Furthermore, the energy used by the heating system comes from at least one of solar power generation, wind power generation, thermal power generation, hydropower generation, grid valley power, and industrial waste heat.

[0013] The present invention also provides a supercritical carbon dioxide coupled molten salt dual-source energy storage method, which is applied to any of the above-mentioned supercritical carbon dioxide coupled molten salt dual-source energy storage systems, and the method comprises: The low-temperature mixture in the low-temperature mixture storage tank is output to the heating system to absorb the heat energy generated by the heating system, so that the low-temperature mixture is heated to obtain a high-temperature mixture; The high temperature mixture in the heating system is output to the high temperature mixture storage tank for storage; The high-temperature mixture in the high-temperature mixture storage tank is output to the gas-liquid separator for gas-liquid separation, so that the high-temperature mixture is separated into first high-temperature supercritical carbon dioxide and high-temperature molten salt; The first high-temperature supercritical carbon dioxide in the gas-liquid separator is output to the power generation system to drive the power generation system to generate electric energy, and the first high-temperature supercritical carbon dioxide is cooled to obtain a first low-temperature supercritical carbon dioxide; The high-temperature molten salt in the gas-liquid separator is output to the heat exchanger for coupling heat exchange with the first low-temperature supercritical carbon dioxide output by the power generation system, so that the high-temperature molten salt is cooled to obtain low-temperature molten salt, and the first low-temperature supercritical carbon dioxide is heated to obtain second high-temperature supercritical carbon dioxide; The second high-temperature supercritical carbon dioxide in the heat exchanger is output to the power generation system to drive the power generation system to generate electric energy, and the second high-temperature supercritical carbon dioxide is cooled to obtain a second low-temperature supercritical carbon dioxide; The low-temperature molten salt in the heat exchanger is output to the low-temperature mixture storage tank for storage. At the same time, the second low-temperature supercritical carbon dioxide in the power generation system is output to the low-temperature mixture storage tank for storage, so that the low-temperature molten salt and the second low-temperature supercritical carbon dioxide are mixed to obtain a low-temperature mixture.

[0014] Further, the high-temperature mixture in the high-temperature mixture storage tank is output to the gas-liquid separator for gas-liquid separation, so that the high-temperature mixture is separated into a first high-temperature supercritical carbon dioxide and a high-temperature molten salt; the first high-temperature supercritical carbon dioxide in the gas-liquid separator is output to the power generation system to drive the power generation system to generate electricity, and the temperature is reduced to obtain a first low-temperature supercritical carbon dioxide; the high-temperature molten salt in the gas-liquid separator is output to the heat exchanger to couple heat exchange with the first low-temperature supercritical carbon dioxide output by the power generation system, so that the high-temperature molten salt is cooled to obtain a low-temperature molten salt, and the first low-temperature supercritical carbon dioxide is heated to obtain a second high-temperature supercritical carbon dioxide; including: The high-temperature mixture in the high-temperature mixture storage tank is output to the gas-liquid separator for gas-liquid separation, so that the high-temperature mixture is separated into the first high-temperature and high-pressure supercritical carbon dioxide and the high-temperature molten salt; The first high-temperature and high-pressure supercritical carbon dioxide in the gas-liquid separator is output to the power generation system to drive the power generation system to generate electric energy, and the first high-temperature and high-pressure supercritical carbon dioxide is cooled and reduced in temperature and pressure to obtain a first low-temperature and low-pressure supercritical carbon dioxide; The first low-temperature, low-pressure supercritical carbon dioxide in the power generation system is output to a first high-pressure compressor, so that the first low-temperature, low-pressure supercritical carbon dioxide is pressurized to obtain a first low-temperature, high-pressure supercritical carbon dioxide; The high-temperature molten salt in the gas-liquid separator is output to the heat exchanger for coupling heat exchange with the first low-temperature and high-pressure supercritical carbon dioxide output by the first high-pressure compressor, so that the high-temperature molten salt is cooled to obtain the low-temperature molten salt, and the first low-temperature and high-pressure supercritical carbon dioxide is heated to obtain a second high-temperature and high-pressure supercritical carbon dioxide.

[0015] Further, the second high-temperature supercritical carbon dioxide in the heat exchanger is output to the power generation system to drive the power generation system to generate electricity, and the second high-temperature supercritical carbon dioxide is cooled to obtain a second low-temperature supercritical carbon dioxide; the low-temperature molten salt in the heat exchanger is output to the low-temperature mixture storage tank for storage, and at the same time, the second low-temperature supercritical carbon dioxide in the power generation system is output to the low-temperature mixture storage tank for storage, so that the low-temperature molten salt is mixed with the second low-temperature supercritical carbon dioxide to obtain a low-temperature mixture; comprising: The second high-temperature and high-pressure supercritical carbon dioxide in the heat exchanger is output to the power generation system to drive the power generation system to generate electric energy, and the second high-temperature and high-pressure supercritical carbon dioxide is cooled and depressurized to obtain a second low-temperature and low-pressure supercritical carbon dioxide; The second low-temperature, low-pressure supercritical carbon dioxide in the power generation system is output to a second high-pressure compressor, so that the second low-temperature, low-pressure supercritical carbon dioxide is pressurized to obtain a second low-temperature, high-pressure supercritical carbon dioxide; The low-temperature molten salt in the heat exchanger is output to the low-temperature mixture storage tank for storage. At the same time, the second low-temperature and high-pressure supercritical carbon dioxide in the second high-pressure compressor is output to the low-temperature mixture storage tank for storage, so that the low-temperature molten salt and the second low-temperature and high-pressure supercritical carbon dioxide are mixed to obtain the low-temperature mixture.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention adopts a strategy of introducing supercritical carbon dioxide into low-temperature molten salt. Supercritical carbon dioxide is used as a solvent, and the solvation effect of supercritical carbon dioxide is used to increase the overall fluidity of the molten salt and reduce the melting point of the molten salt. This strategy effectively prevents the molten salt from solidifying and freezing the pipeline in the low-temperature zone, and provides a new idea for preventing the solidification of molten salt.

[0017] 2. The present invention adopts a dual heat storage medium strategy of supercritical carbon dioxide coupled with molten salt. Supercritical carbon dioxide can be used as a heat storage medium, which can convert most of the thermal energy into internal energy for storage. Finally, the internal energy is released as needed and converted into mechanical energy for power generation. This strategy greatly improves the energy storage efficiency of traditional molten salt energy storage systems. At the same time, the energy storage efficiency of traditional supercritical carbon dioxide power generation systems is optimized by utilizing the high specific heat capacity of molten salt working fluid. In addition, supercritical carbon dioxide can be used as a heat transfer medium with a density close to that of liquid, while its viscosity and diffusion coefficient are close to those of gas, which can accelerate the heat absorption and heat release rates of molten salt working fluid, realize efficient heat transfer of the main thermal processes of the system and rapid response to the peak load demand of the power grid, and improve the efficiency and diversity of the energy storage system.

[0018] 3. The present invention adopts the strategy of supercritical carbon dioxide Brayton cycle for power generation. Supercritical carbon dioxide has great advantages in energy storage density, system heat absorption and heat release efficiency and cost per kilowatt-hour. Its dual-source energy storage system composed of coupled molten salt has the advantages of high energy storage density of supercritical carbon dioxide power generation system and high heat capacity of molten salt energy storage system. Compared with systems using other fluids as working fluids, it has the advantages of higher efficiency, more compact structure and lower cost. Therefore, the supercritical carbon dioxide coupled molten salt dual-source energy storage system has excellent economic benefits and application prospects.

[0019] 4. Since the supercritical carbon dioxide coupled molten salt dual-source energy storage method provided by the present invention is realized by the above-mentioned supercritical carbon dioxide coupled molten salt dual-source energy storage system, and this supercritical carbon dioxide coupled molten salt dual-source energy storage method includes the technical solution of the above-mentioned supercritical carbon dioxide coupled molten salt dual-source energy storage system, it has the corresponding technical effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings: Figure 1 A schematic diagram of the structure of a supercritical carbon dioxide coupled molten salt dual-source energy storage system provided in an embodiment of the present invention; Figure 2 An HP-DSC curve diagram of solar salt at normal pressure in a supercritical carbon dioxide coupled molten salt dual-source energy storage method provided in an embodiment of the present invention; Figure 3 In a supercritical carbon dioxide coupled molten salt dual-source energy storage method provided in an embodiment of the present invention, solar salt is HP-DSC curve under 8 MPa CO2.

[0021] In the figure: 1. Low-temperature mixture storage tank; 2. High-temperature heater; 3. High-temperature mixture storage tank; 4. Gas-liquid separator; 5. Heat exchanger; 6. First high-pressure compressor; 7. Turbine; 8. Second high-pressure compressor; 9. Safety valve. DETAILED DESCRIPTION

[0022] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0023] See also Figure 1 , an embodiment of the present invention provides a supercritical carbon dioxide coupled molten salt dual-source energy storage system, including a low-temperature mixture storage tank 1, a heating system, a high-temperature mixture storage tank 3, a gas-liquid separator 4, a heat exchanger 5 and a power generation system; The mixture output end of the low-temperature mixture storage tank 1 is connected to the mixture input end of the heating system, the mixture output end of the heating system is connected to the mixture input end of the high-temperature mixture storage tank 3, the mixture output end of the high-temperature mixture storage tank 3 is connected to the mixture input end of the gas-liquid separator 4, the gas-liquid separator 4 is used to separate the mixture into supercritical carbon dioxide and molten salt, the gas output end of the gas-liquid separator 4 is connected to the first gas input end of the power generation system, the molten salt output end of the gas-liquid separator 4 is connected to the molten salt input end of the heat exchanger 5, the molten salt output end of the heat exchanger 5 is connected to the molten salt input end of the low-temperature mixture storage tank 1, the first gas output end of the power generation system is connected to the gas input end of the heat exchanger 5, the gas output end of the heat exchanger 5 is connected to the second gas input end of the power generation system, and the second gas output end of the power generation system is connected to the gas input end of the low-temperature mixture storage tank 1.

[0024] In a specific embodiment, the supercritical carbon dioxide coupled molten salt dual-source energy storage system further includes a first high-pressure compressor 6 and a second high-pressure compressor 8; The mixture output end of the low-temperature mixture storage tank 1 is connected to the mixture input end of the heating system, the mixture output end of the heating system is connected to the mixture input end of the high-temperature mixture storage tank 3, the mixture output end of the high-temperature mixture storage tank 3 is connected to the mixture input end of the gas-liquid separator 4, the gas-liquid separator 4 is used to separate the mixture into supercritical carbon dioxide and molten salt, the gas output end of the gas-liquid separator 4 is connected to the first gas input end of the power generation system, the molten salt output end of the gas-liquid separator 4 is connected to the molten salt input end of the heat exchanger 5, the molten salt output end of the heat exchanger 5 is connected to the molten salt input end of the low-temperature mixture storage tank 1, the first gas output end of the power generation system is connected to the gas input end of the first high-pressure compressor 6, the gas output end of the first high-pressure compressor 6 is connected to the gas input end of the heat exchanger 5, the gas output end of the heat exchanger 5 is connected to the second gas input end of the power generation system, the second gas output end of the power generation system is connected to the gas input end of the second high-pressure compressor 8, and the gas output end of the second high-pressure compressor 8 is connected to the gas input end of the low-temperature mixture storage tank 1.

[0025] Among them, supercritical carbon dioxide can be supplemented by a specific CO2 capture system, and the pressure of supercritical carbon dioxide can be selected as 6 MPa~30 MPa according to the specific application scenario; the heating system selects at least one of a high-temperature heater 2, a concentrating collector tower, a trough collector, a dish collector, a trough collector, a linear Fresnel collector, an industrial waste heat collector, and an industrial steam heat exchanger, and the energy used by the heating system comes from at least one of solar power generation, wind power generation, thermal power generation, hydropower generation, grid valley power, and industrial waste heat; the molten salt selects any one of solar salt, Hitec salt, Hitec XL salt, chloride salt, and carbonate; the heat exchanger 5 can be directly connected to other heating application modules; the power generation system adopts a turbine 7; the first high-pressure compressor 6 and the second high-pressure compressor 8 can be driven by the abandoned electricity of new energy, the electricity of the power generation system or the electricity of the thermal power plant.

[0026] In an optional embodiment, safety valves 9 are provided between the low-temperature mixture storage tank 1 and the heating system, between the heating system and the high-temperature mixture storage tank 3, between the high-temperature mixture storage tank 3 and the gas-liquid separator 4, between the gas-liquid separator 4 and the power generation system, between the power generation system and the first high-pressure compressor 6, between the heat exchanger 5 and the power generation system, between the heat exchanger 5 and the low-temperature mixture storage tank 1, between the power generation system and the second high-pressure compressor 8, and between the second high-pressure compressor 8 and the low-temperature mixture storage tank 1.

[0027] In an actual application scenario, the supercritical carbon dioxide coupled molten salt dual-source energy storage system includes a low-temperature mixture storage tank 1, a high-temperature heater 2, a high-temperature mixture storage tank 3, a gas-liquid separator 4, a molten salt-carbon dioxide heat exchanger, a high-pressure compressor, a turbine 7, and a safety valve 9; An operating method of the above-mentioned supercritical carbon dioxide coupled molten salt dual-source energy storage system includes the following stages: 1. Heat storage and heat exchange stage: When the solar thermal energy storage or the power grid stores surplus electric energy, the mixture of supercritical carbon dioxide and molten salt in the low-temperature mixture storage tank 1 enters the high-temperature heater 2 and enters the working medium side of the high-temperature heater 2; the low-temperature molten salt in the low-temperature mixture storage tank 1 can flow into the high-temperature heater 2 more quickly under the pressure of supercritical carbon dioxide. The high-temperature heater uses the input of energy such as solar thermal, photovoltaic, thermal power, and wind power to heat the mixture of low-temperature molten salt and supercritical carbon dioxide, and the high-temperature mixture after absorbing heat is stored in the high-temperature mixture storage tank 3.

[0028] Among them, the pressure of supercritical carbon dioxide can be selected as 6 MPa~30 MPa according to the specific application scenario.

[0029] Among them, the molten salt can be selected from solar salt, Hitec salt, Hitec XL salt, chloride salt and carbonate according to the specific application environment.

[0030] Among them, the high temperature heater 2 can be replaced by any one of a concentrating solar collector tower, a trough collector, a dish collector, a trough collector, a linear Fresnel collector, an industrial waste heat collector, and an industrial steam heat exchanger.

[0031] 2. Energy conversion stage: When electrical energy or heat energy output is required, the high-temperature molten salt and supercritical carbon dioxide mixed working fluid first enters the gas-liquid separator 4 to separate the supercritical carbon dioxide and the high-temperature molten salt. The supercritical carbon dioxide separation side is directly connected to the turbine 7, while the high-temperature molten salt separation side is connected to the molten salt-carbon dioxide heat exchanger. On the one hand, supercritical carbon dioxide expands rapidly after absorbing heat, converting thermal energy into internal energy for storage. After entering the turbine 7, the internal energy is quickly converted into mechanical energy for power generation, and then enters the high-pressure compressor for recycling. On the other hand, the high-temperature molten salt enters the molten salt-carbon dioxide heat exchanger to heat the supercritical carbon dioxide working fluid for Brayton cycle power generation, and then enters the low-temperature mixture storage tank 1.

[0032] Among them, supercritical carbon dioxide can be supplemented by a specific CO2 capture system.

[0033] Among them, the molten salt-carbon dioxide heat exchanger is a key component in the supercritical carbon dioxide coupled molten salt dual-source energy storage system. One side contains normal pressure and high-temperature molten salt, and the other side contains high-temperature and high-pressure supercritical carbon dioxide.

[0034] Among them, the molten salt-carbon dioxide heat exchanger can be directly connected to other heating application modules.

[0035] 3. Low temperature molten salt storage stage: After the molten salt completes the heat exchange, it enters the low-temperature mixture storage tank 1 for storage. Then, 6MPa~30MPa supercritical carbon dioxide is compressed into the high-pressure compressor, and the solvation effect of supercritical carbon dioxide is used to reduce the viscosity of the low-temperature molten salt and maintain its certain fluidity.

[0036] Among them, the high-pressure compressor can be driven by the abandoned electricity of new energy, the electricity of the power generation system or the electricity of the thermal power plant.

[0037] Among them, the low-temperature molten salt can be insulated first by an electric heater or by using a technical solution of coupling supercritical carbon dioxide and an electric heater.

[0038] The combination of molten salt and supercritical carbon dioxide in this technology is expected to become the most promising combined heat transfer medium in the third generation of solar thermal power generation.

[0039] In the supercritical carbon dioxide coupled molten salt dual-source energy storage system of this embodiment, a strategy of introducing supercritical carbon dioxide into low-temperature molten salt is adopted. Supercritical carbon dioxide is used as a solvent, and the solvation effect of supercritical carbon dioxide is used to increase the overall fluidity of the molten salt and reduce the melting point of the molten salt. This strategy effectively prevents the molten salt from solidifying and freezing the pipeline in the low-temperature zone, and provides a new idea for preventing the solidification of molten salt. The strategy of supercritical carbon dioxide coupling molten salt dual heat storage medium is adopted. Supercritical carbon dioxide can be used as a heat storage medium, which can convert most of the thermal energy into internal energy for storage. Finally, the internal energy is released as needed and converted into mechanical energy for power generation. This strategy greatly improves the energy storage efficiency of the traditional molten salt energy storage system. At the same time, the energy storage efficiency of the traditional supercritical carbon dioxide power generation system is optimized by utilizing the high specific heat capacity of the molten salt working fluid. In addition, supercritical carbon dioxide can be used as a heat transfer medium, whose density is close to that of liquid, while the viscosity and diffusion coefficient are close to that of gas, which can accelerate the heat absorption and heat release rate of the molten salt working fluid, realize the efficient heat transfer of the main thermodynamic process of the system and quickly respond to the peak load demand of the power grid, and improve the efficiency and diversity of the energy storage system. The strategy of supercritical carbon dioxide Brayton cycle for power generation is adopted. Supercritical carbon dioxide has great advantages in energy storage density, system heat absorption and heat release efficiency and cost per kilowatt-hour. Its dual-source energy storage system composed of coupled molten salt has the advantages of high energy storage density of supercritical carbon dioxide power generation system and high heat capacity of molten salt energy storage system. Compared with systems using other fluids as working fluids, it has the advantages of higher efficiency, more compact structure and lower cost. Therefore, the supercritical carbon dioxide coupled molten salt dual-source energy storage system has excellent economic benefits and application prospects.

[0040] See also Figure 1 The embodiment of the present invention provides a supercritical carbon dioxide coupled molten salt dual-source energy storage method, which is applied to a supercritical carbon dioxide coupled molten salt dual-source energy storage system described in Example 1, and the method includes: The low-temperature mixture in the low-temperature mixture storage tank 1 is output to the heating system to absorb the heat energy generated by the heating system, so that the low-temperature mixture is heated to obtain a high-temperature mixture; The high-temperature mixture in the heating system is output to the high-temperature mixture storage tank 3 for storage; The high-temperature mixture in the high-temperature mixture storage tank 3 is output to the gas-liquid separator 4 for gas-liquid separation, so that the high-temperature mixture is separated into the first high-temperature supercritical carbon dioxide and the high-temperature molten salt; The first high-temperature supercritical carbon dioxide in the gas-liquid separator 4 is output to the power generation system to drive the power generation system to generate electric energy, and the first high-temperature supercritical carbon dioxide is cooled to obtain the first low-temperature supercritical carbon dioxide; The high-temperature molten salt in the gas-liquid separator 4 is output to the heat exchanger 5 for coupling heat exchange with the first low-temperature supercritical carbon dioxide output by the power generation system, so that the high-temperature molten salt is cooled to obtain low-temperature molten salt, and the first low-temperature supercritical carbon dioxide is heated to obtain the second high-temperature supercritical carbon dioxide; The second high-temperature supercritical carbon dioxide in the heat exchanger 5 is output to the power generation system to drive the power generation system to generate electricity, and the second high-temperature supercritical carbon dioxide is cooled to obtain the second low-temperature supercritical carbon dioxide; The low-temperature molten salt in the heat exchanger 5 is output to the low-temperature mixture storage tank 1 for storage. At the same time, the second low-temperature supercritical carbon dioxide in the power generation system is output to the low-temperature mixture storage tank 1 for storage, so that the low-temperature molten salt and the second low-temperature supercritical carbon dioxide are mixed to obtain a low-temperature mixture.

[0041] In a specific embodiment, the supercritical carbon dioxide coupled molten salt dual-source energy storage system further includes a first high-pressure compressor 6 and a second high-pressure compressor 8. At this time, the supercritical carbon dioxide coupled molten salt dual-source energy storage method includes: The low-temperature mixture in the low-temperature mixture storage tank 1 is output to the heating system to absorb the heat energy generated by the heating system, so that the low-temperature mixture is heated to obtain a high-temperature mixture; The high-temperature mixture in the heating system is output to the high-temperature mixture storage tank 3 for storage; The high-temperature mixture in the high-temperature mixture storage tank 3 is output to the gas-liquid separator 4 for gas-liquid separation, so that the high-temperature mixture is separated into the first high-temperature and high-pressure supercritical carbon dioxide and high-temperature molten salt; The first high-temperature and high-pressure supercritical carbon dioxide in the gas-liquid separator 4 is output to the power generation system to drive the power generation system to generate electric energy, and the first high-temperature and high-pressure supercritical carbon dioxide is cooled and depressurized to obtain the first low-temperature and low-pressure supercritical carbon dioxide; The first low-temperature, low-pressure supercritical carbon dioxide in the power generation system is output to the first high-pressure compressor 6, so that the first low-temperature, low-pressure supercritical carbon dioxide is pressurized to obtain the first low-temperature, high-pressure supercritical carbon dioxide; The high-temperature molten salt in the gas-liquid separator 4 is output to the heat exchanger 5 for coupling heat exchange with the first low-temperature and high-pressure supercritical carbon dioxide output by the first high-pressure compressor 6, so that the high-temperature molten salt is cooled to obtain low-temperature molten salt, and the first low-temperature and high-pressure supercritical carbon dioxide is heated to obtain the second high-temperature and high-pressure supercritical carbon dioxide; The second high temperature and high pressure supercritical carbon dioxide in the heat exchanger 5 is output to the power generation system to drive the power generation system to generate electric energy, and the second high temperature and high pressure supercritical carbon dioxide is cooled and depressurized to obtain the second low temperature and low pressure supercritical carbon dioxide; The second low-temperature and low-pressure supercritical carbon dioxide in the power generation system is output to the second high-pressure compressor 8, so that the second low-temperature and low-pressure supercritical carbon dioxide is pressurized to obtain the second low-temperature and high-pressure supercritical carbon dioxide; The low-temperature molten salt in the heat exchanger 5 is output to the low-temperature mixture storage tank 1 for storage. At the same time, the second low-temperature and high-pressure supercritical carbon dioxide in the second high-pressure compressor 8 is output to the low-temperature mixture storage tank 1 for storage, so that the low-temperature molten salt and the second low-temperature and high-pressure supercritical carbon dioxide are mixed to obtain a low-temperature mixture.

[0042] In a specific implementation scenario, this supercritical carbon dioxide coupled molten salt dual-source energy storage method mainly includes a heat storage and exchange stage, an energy conversion stage, and a low-temperature molten salt storage stage. When the solar thermal storage or the power grid stores surplus electric energy, the mixture of 8 MPa supercritical carbon dioxide and solar salt in the low-temperature mixture storage tank 1 enters the high-temperature heater 2 and enters the working fluid side of the high-temperature heater 2; the low-temperature molten salt in the low-temperature mixture storage tank 1 can flow into the high-temperature heater 2 more quickly under the pressure of supercritical carbon dioxide. The high-temperature heater 2 uses the input of wind power to heat the low-temperature molten salt and supercritical carbon dioxide mixed working fluid, and the high-temperature mixed working fluid after absorbing heat is stored in the high-temperature mixture storage tank 3. When electric energy output is required, the high-temperature molten salt and supercritical carbon dioxide mixed working fluid in the high-temperature mixture storage tank 3 first enter the gas-liquid separator 4 to separate the supercritical carbon dioxide and the high-temperature molten salt. The supercritical carbon dioxide separation side is directly connected to the turbine 7, and the high-temperature molten salt separation side is connected to the molten salt-carbon dioxide heat exchanger. One side contains normal pressure high-temperature molten salt, and the other side contains high-temperature and high-pressure supercritical carbon dioxide. On the one hand, supercritical carbon dioxide expands rapidly after absorbing heat, converting heat energy into internal energy for storage. After entering the turbine 7, the internal energy is quickly converted into mechanical energy for power generation, and then the carbon dioxide enters the high-pressure compressor for recycling. On the other hand, the high-temperature molten salt enters the molten salt heat exchanger to heat the supercritical carbon dioxide working fluid for Brayton cycle power generation. When the molten salt completes the heat exchange, it enters the low-temperature mixture storage tank 1 for storage. Then, 8 MPa supercritical carbon dioxide is pressed into the high-pressure compressor, and the solvation effect of supercritical carbon dioxide is used to reduce the viscosity of the low-temperature molten salt and maintain its certain fluidity.

[0043] The solar salt was scanned non-isothermally in a CO2-free environment and in an 8 MPa CO2 environment by high pressure differential scanning calorimetry. Figure 2 As shown in Figure 2, the melting point of solar salt under normal conditions is 221.7 °C, which is consistent with the relevant references. Figure 3 As shown in the figure, the melting point of solar salt under 8 MPa CO2 conditions is 206.7 ℃, which is 15.0 ℃ lower than that under normal conditions.

[0044] Table 1 Test samples Starting point (℃) Peak value (℃) End point (℃) Normal pressure 183.9±0.4 221.7±0.2 268.2±0.6 8 MPa CO2 175.2±0.3 206.7±0.5 248.9±0.4 Analytical test methods: High Pressure Differential Scanning Calorimetry Analysis: A high pressure differential scanning calorimeter (HP-DSC) was used to conduct thermal analysis experiments on solar salt samples. The analytical instrument was a DSC 204HP high pressure differential scanning calorimeter from Netzsch±, Germany. 10 mg of sample was weighed (the error was less than 0.01 mg), and the heating rate was set to 15 ℃ / min. When testing under normal pressure conditions, 0.1 MPa N2 was selected as the protective gas to prevent furnace contamination. When testing under 8 MPa CO2 conditions, N was not required. 2。 Before the experiment, the CO2 pressure was adjusted to 8 MPa and the initial temperature was adjusted to 40 °C.

[0045] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present invention and the features in the embodiments can be arbitrarily combined with each other.

Claims

1. A supercritical carbon dioxide coupled molten salt dual-source energy storage system, characterized in that: It comprises a low-temperature mixture storage tank (1), a heating system, a high-temperature mixture storage tank (3), a gas-liquid separator (4), a heat exchanger (5) and a power generation system; The mixture output end of the low-temperature mixture storage tank (1) is connected to the mixture input end of the heating system, the mixture output end of the heating system is connected to the mixture input end of the high-temperature mixture storage tank (3), the mixture output end of the high-temperature mixture storage tank (3) is connected to the mixture input end of the gas-liquid separator (4), the gas-liquid separator (4) is used to separate the mixture into supercritical carbon dioxide and molten salt, the gas output end of the gas-liquid separator (4) is connected to the first gas input end of the power generation system, the molten salt output end of the gas-liquid separator (4) is connected to the molten salt input end of the heat exchanger (5), the molten salt output end of the heat exchanger (5) is connected to the molten salt input end of the low-temperature mixture storage tank (1), the first gas output end of the power generation system is connected to the gas input end of the heat exchanger (5), the gas output end of the heat exchanger (5) is connected to the second gas input end of the power generation system, and the second gas output end of the power generation system is connected to the gas input end of the low-temperature mixture storage tank (1).

2. A supercritical carbon dioxide coupled molten salt dual-source energy storage system according to claim 1, characterized in that: Also includes a first high-pressure compressor (6); The first gas output end of the power generation system is connected to the gas input end of the first high-pressure compressor (6), and the gas output end of the first high-pressure compressor (6) is connected to the gas input end of the heat exchanger (5).

3. A supercritical carbon dioxide coupled molten salt dual-source energy storage system according to claim 1 or 2, characterized in that: Also includes a second high-pressure compressor (8); The second gas output end of the power generation system is connected to the gas input end of the second high-pressure compressor (8), and the gas output end of the second high-pressure compressor (8) is connected to the gas input end of the low-temperature mixture storage tank (1).

4. A supercritical carbon dioxide coupled molten salt dual-source energy storage system according to claim 1, characterized in that: The heating system uses at least one of a high temperature heater (2), a concentrating heat collection tower, a trough collector, a dish collector, a trough collector, a linear Fresnel collector, an industrial waste heat collector, and an industrial steam heat exchanger.

5. A supercritical carbon dioxide coupled molten salt dual-source energy storage system according to claim 1, characterized in that: The molten salt is selected from any one of solar salt, Hitec salt, Hitec XL salt, chloride salt and carbonate salt.

6. A supercritical carbon dioxide coupled molten salt dual-source energy storage system according to claim 1, characterized in that: The power generation system adopts a turbine (7).

7. A supercritical carbon dioxide coupled molten salt dual-source energy storage system according to claim 1 or 4, characterized in that: The energy used by the heating system comes from at least one of solar power generation, wind power generation, thermal power generation, hydropower generation, grid valley power generation, and industrial waste heat.

8. A supercritical carbon dioxide coupled molten salt dual-source energy storage method, applied to a supercritical carbon dioxide coupled molten salt dual-source energy storage system as claimed in any one of claims 1 to 7, characterized in that: The method comprises: The low-temperature mixture in the low-temperature mixture storage tank (1) is output to the heating system to absorb the heat energy generated by the heating system, thereby heating the low-temperature mixture to obtain a high-temperature mixture; The high-temperature mixture in the heating system is output to the high-temperature mixture storage tank (3) for storage; The high-temperature mixture in the high-temperature mixture storage tank (3) is output to the gas-liquid separator (4) for gas-liquid separation, so that the high-temperature mixture is separated into first high-temperature supercritical carbon dioxide and high-temperature molten salt; The first high-temperature supercritical carbon dioxide in the gas-liquid separator (4) is output to the power generation system to drive the power generation system to generate electric energy, and the first high-temperature supercritical carbon dioxide is cooled to obtain a first low-temperature supercritical carbon dioxide; The high-temperature molten salt in the gas-liquid separator (4) is output to the heat exchanger (5) for coupled heat exchange with the first low-temperature supercritical carbon dioxide output by the power generation system, so that the high-temperature molten salt is cooled to obtain low-temperature molten salt, and the first low-temperature supercritical carbon dioxide is heated to obtain second high-temperature supercritical carbon dioxide; The second high-temperature supercritical carbon dioxide in the heat exchanger (5) is output to the power generation system to drive the power generation system to generate electric energy, and the second high-temperature supercritical carbon dioxide is cooled to obtain a second low-temperature supercritical carbon dioxide; The low-temperature molten salt in the heat exchanger (5) is output to the low-temperature mixture storage tank (1) for storage, and at the same time, the second low-temperature supercritical carbon dioxide in the power generation system is output to the low-temperature mixture storage tank (1) for storage, so that the low-temperature molten salt and the second low-temperature supercritical carbon dioxide are mixed to obtain a low-temperature mixture.

9. A supercritical carbon dioxide coupled molten salt dual-source energy storage method according to claim 8, characterized in that: The high-temperature mixture in the high-temperature mixture storage tank (3) is output to the gas-liquid separator (4) for gas-liquid separation, so that the high-temperature mixture is separated into a first high-temperature supercritical carbon dioxide and a high-temperature molten salt; the first high-temperature supercritical carbon dioxide in the gas-liquid separator (4) is output to the power generation system to drive the power generation system to generate electric energy, and is cooled to obtain a first low-temperature supercritical carbon dioxide; the high-temperature molten salt in the gas-liquid separator (4) is output to the heat exchanger (5) for coupled heat exchange with the first low-temperature supercritical carbon dioxide output by the power generation system, so that the high-temperature molten salt is cooled to obtain a low-temperature molten salt, and the first low-temperature supercritical carbon dioxide is heated to obtain a second high-temperature supercritical carbon dioxide; comprising: The high-temperature mixture in the high-temperature mixture storage tank (3) is output to the gas-liquid separator (4) for gas-liquid separation, so that the high-temperature mixture is separated into the first high-temperature and high-pressure supercritical carbon dioxide and the high-temperature molten salt; The first high-temperature and high-pressure supercritical carbon dioxide in the gas-liquid separator (4) is output to the power generation system to drive the power generation system to generate electric energy, and the first high-temperature and high-pressure supercritical carbon dioxide is cooled and reduced in temperature and pressure to obtain a first low-temperature and low-pressure supercritical carbon dioxide; The first low-temperature, low-pressure supercritical carbon dioxide in the power generation system is output to a first high-pressure compressor (6), so that the first low-temperature, low-pressure supercritical carbon dioxide is pressurized to obtain first low-temperature, high-pressure supercritical carbon dioxide; The high-temperature molten salt in the gas-liquid separator (4) is output to the heat exchanger (5) for coupled heat exchange with the first low-temperature and high-pressure supercritical carbon dioxide output by the first high-pressure compressor (6), so that the high-temperature molten salt is cooled to obtain the low-temperature molten salt, and the first low-temperature and high-pressure supercritical carbon dioxide is heated to obtain the second high-temperature and high-pressure supercritical carbon dioxide.

10. A supercritical carbon dioxide coupled molten salt dual-source energy storage method according to claim 9, characterized in that: The second high-temperature supercritical carbon dioxide in the heat exchanger (5) is output to the power generation system to drive the power generation system to generate electric energy, and the second high-temperature supercritical carbon dioxide is cooled to obtain second low-temperature supercritical carbon dioxide; the low-temperature molten salt in the heat exchanger (5) is output to the low-temperature mixture storage tank (1) for storage, and at the same time, the second low-temperature supercritical carbon dioxide in the power generation system is output to the low-temperature mixture storage tank (1) for storage, so that the low-temperature molten salt is mixed with the second low-temperature supercritical carbon dioxide to obtain a low-temperature mixture; comprising: The second high-temperature and high-pressure supercritical carbon dioxide in the heat exchanger (5) is output to the power generation system to drive the power generation system to generate electric energy, and the second high-temperature and high-pressure supercritical carbon dioxide is cooled and reduced in temperature and pressure to obtain a second low-temperature and low-pressure supercritical carbon dioxide; The second low-temperature, low-pressure supercritical carbon dioxide in the power generation system is output to a second high-pressure compressor (8), so that the second low-temperature, low-pressure supercritical carbon dioxide is pressurized to obtain second low-temperature, high-pressure supercritical carbon dioxide; The low-temperature molten salt in the heat exchanger (5) is output to the low-temperature mixture storage tank (1) for storage, and at the same time, the second low-temperature and high-pressure supercritical carbon dioxide in the second high-pressure compressor (8) is output to the low-temperature mixture storage tank (1) for storage, so that the low-temperature molten salt and the second low-temperature and high-pressure supercritical carbon dioxide are mixed to obtain the low-temperature mixture.

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