Multi-energy combined supply system based on transcritical cycle

Abstract

The utility model provides a transcritical cycle-based multi-energy combined supply system. The transcritical cycle-based multi-energy combined supply system comprises a clean energy utilization system, an energy storage system, a supercritical medium power generation system, a supercritical medium refrigeration system, a combined heat and power generation system and a control system, the supercritical medium power generation system comprises a first gas-liquid separator, a compressor and a high-pressure turbine; the output end of the heat storage system is connected with the input end of the first gas-liquid separator, the energy storage medium output end of the first gas-liquid separator is connected with the input end of the combined heat and power generation system, the supercritical medium output end of the first gas-liquid separator is connected with the first input end of the compressor, and the first output end of the compressor is connected with the input end of the high-pressure turbine. The second output end of the compressor is connected with the supercritical medium input end of the cold storage system. According to the scheme, through coupling application of a supercritical medium technology and an energy storage medium heat storage technology, a comprehensive energy service system integrating efficient energy conversion, flexible energy storage adjustment and multifunctional cooling, heating and power supply is constructed.

Description

Technical Field

[0001] This utility model relates to the field of multi-energy supply technology, specifically to a multi-energy supply system based on transcritical cycle. Background Technology

[0002] Against the backdrop of the new era of energy transformation, integrated energy systems are emerging and flourishing. As an advanced energy utilization model integrating high efficiency, cleanliness, and flexibility, integrated energy systems can not only significantly promote the large-scale consumption of renewable energy but also greatly improve overall energy utilization efficiency while effectively reducing carbon emissions, thus meeting the demands of sustainable development. Among numerous energy utilization technologies, supercritical CO2 cycle technology has attracted widespread attention due to its significant thermal efficiency and excellent flexibility. On the one hand, supercritical CO2 has low viscosity and high thermal conductivity, enabling it to achieve efficient heat transfer with minimal energy loss during energy transmission. Brayton or Rankine cycles using supercritical CO2 as the working fluid are simplified, compact, efficient, and air-coolable, and can be combined with various heat sources to form efficient power generation systems. On the other hand, CO2's critical point is 31.3℃ / 7.38MPa, making it an excellent working fluid for transcritical refrigeration cycles. CO2 exhibits excellent environmental performance, low cost, easy availability, good stability, and is beneficial for reducing the size of refrigeration equipment. In the CO2 transcritical refrigeration cycle, the heat absorption process takes place under subcritical conditions, relying on liquid evaporation for cooling, resulting in excellent cooling performance. Meanwhile, molten salt thermal energy storage technology offers advantages such as large energy storage capacity, long storage period, and low cost, meeting various application requirements from low to high temperatures. This makes it a promising technology for applications in concentrated solar power (CSP) and industrial heating.

[0003] Traditional combined energy systems often suffer from low energy conversion efficiency and poor stability, failing to fully utilize energy. Publication patent CN117213101A discloses a combined energy system incorporating energy storage, utilizing the heat of compression during the compression process, or using the heat of compression to drive a lithium bromide unit for cooling, to meet users' heating and cooling needs. However, the temperature and flow rate of the heat of compression are unstable, making it difficult to meet the stable operation requirements of the lithium bromide unit. Secondly, the cooling or heating efficiency of the lithium bromide unit may be affected by the supply of heat of compression, leading to unstable cooling or heating effects. Furthermore, the utilization of heat of compression may be limited by season and ambient temperature; in high-temperature environments, the utilization efficiency of heat of compression may decrease. Publication patent CN111140445A discloses a gas-steam combined cycle combined cooling, heating, and power system, combining a gas turbine and a steam power unit to improve thermal energy utilization. However, although the exhaust gas from the gas turbine can be distributed to the cooling and heating branches through a flow control device, the temperature and pressure of the exhaust gas may not fully meet the needs of the lithium bromide cooling and heating systems, resulting in energy waste. Furthermore, as a fossil fuel, natural gas has limited reserves, and long-term reliance on natural gas supply may affect the sustainability of the system.

[0004] In molten salt thermal storage systems, the viscosity of molten salt increases significantly in the low-temperature region, leading to decreased fluidity. This not only increases pumping difficulty but can also cause freezing problems. Patent CN118999017A utilizes waste heat and stored heat from the cold end of a supercritical carbon dioxide cycle for heating, coupled with an improved carbon dioxide cycle for refrigeration, achieving combined cooling, heating, and power (CCHP). This system uses an electric heater to heat the molten salt to prevent freezing. However, this strategy is prone to uneven heating and localized overheating of the molten salt. The additional energy input leads to energy waste and increased operating costs.

[0005] In summary, the existing technology has the following drawbacks:

[0006] 1. Existing energy systems mostly employ a single energy conversion model, such as heat-to-electricity, electricity-to-cooling, or solar-to-electricity. However, significant energy losses occur during the conversion from one form to another, resulting in a low percentage of effectively utilized energy. For example, a large amount of heat energy is not effectively utilized in traditional thermal power generation, with energy conversion efficiency typically only around 30%-40%. Furthermore, this conversion model also offers relatively limited supply to users, failing to meet diverse user needs and seasonal energy demand fluctuations.

[0007] 2. Existing integrated energy systems often employ multiple systems coupled together to meet the needs of diverse energy supply and seasonal energy demand changes. However, the integration level between most different energy systems is not high enough, and coordination and optimization between subsystems are difficult, making it hard to achieve true multi-energy complementarity and synergistic optimization, thus limiting the overall performance and efficiency improvement of integrated energy systems.

[0008] 3. The fluidity of existing single molten salt working fluid decreases sharply in the low temperature range, which not only increases the difficulty of pumping, but may also cause the molten salt system to solidify, resulting in "freezing blockage", damaging system equipment and seriously affecting the safety of energy storage system. Utility Model Content

[0009] To address the shortcomings of existing technologies, the purpose of this invention is to provide a multi-energy combined supply system based on transcritical cycles. By coupling supercritical medium technology with energy storage medium thermal storage technology, a comprehensive energy service system integrating efficient energy conversion, flexible energy storage regulation, and multi-functional cooling, heating, and power supply is constructed, thereby achieving efficient energy utilization and sustainable development.

[0010] To solve the above-mentioned technical problems, this utility model provides a multi-energy combined supply system based on transcritical cycle, including a clean energy utilization system, an energy storage system, a supercritical medium power generation system, a supercritical medium refrigeration system, a combined heat and power system, and a control system. The clean energy utilization system, the energy storage system, the supercritical medium power generation system, the supercritical medium refrigeration system, and the combined heat and power system are respectively electrically connected to the control system.

[0011] The energy storage system includes a thermal storage system and a cold storage system. The output end of the cold storage system is connected to the input end of the clean energy utilization system, and the output end of the clean energy utilization system is connected to the input end of the thermal storage system, so that the low-temperature mixed working fluid stored in the cold storage system is heated by the clean energy utilization system to obtain a high-temperature mixed working fluid, which is then stored in the thermal storage system.

[0012] The supercritical medium power generation system includes a first gas-liquid separator, a compressor, and a high-pressure turbine. The output end of the thermal energy storage system is connected to the input end of the first gas-liquid separator, and the energy storage medium output end of the first gas-liquid separator is connected to the input end of the combined heat and power system, so that the high-temperature energy storage medium enters the combined heat and power system to generate electrical energy and / or thermal energy. The supercritical medium output end of the first gas-liquid separator is connected to the first input end of the compressor, so that the supercritical medium is pressurized under the action of the compressor. The first output end of the compressor is connected to the input end of the high-pressure turbine, so that the supercritical medium enters the high-pressure turbine to do work and generate electrical energy. The electrical energy output end of the high-pressure turbine is connected to the user end to supply the user end with the electrical energy generated by the supercritical medium entering the high-pressure turbine. The second output end of the compressor is connected to the supercritical medium input end of the cold storage system to realize the recycling of the supercritical medium.

[0013] The supercritical medium output end of the high-pressure turbine is connected to the first input end of the supercritical medium refrigeration system, and the first output end of the compressor is also connected to the second input end of the supercritical medium refrigeration system, so that the supercritical medium output by the high-pressure turbine and / or the compressor enters the supercritical medium refrigeration system to achieve refrigeration. The return end of the supercritical medium refrigeration system is connected to the second input end of the compressor to realize the recycling of the supercritical medium. The output end of the supercritical medium refrigeration system is connected to the user end to supply the cold energy generated by the supercritical medium refrigeration system to the user end.

[0014] The energy output end of the cogeneration system is connected to the user end, and is used to supply the electrical energy and / or heat energy generated by the cogeneration system to the user end. The energy storage medium output end of the cogeneration system is connected to the energy storage medium input end of the cold storage system, and is used to return the low-temperature energy storage medium obtained by the high-temperature energy storage medium through heat exchange in the cogeneration system to the cold storage system, so as to realize the recycling of the energy storage medium.

[0015] Furthermore, the supercritical medium power generation system also includes a pressure detector. The supercritical medium output terminal of the first gas-liquid separator is connected to the input terminal of the pressure detector, and the output terminal of the pressure detector is connected to the first input terminal of the compressor. The pressure detector is used to monitor the pressure of the supercritical medium output by the first gas-liquid separator, so that the control system can regulate the multi-energy power generation system according to the monitoring results.

[0016] Furthermore, the supercritical medium refrigeration system includes a first ejector, a second ejector, a second gas-liquid separator, and an air-cooling system;

[0017] The supercritical medium output end of the high-pressure turbine is connected to the input end of the first ejector, the return end of the first ejector is connected to the second input end of the compressor, the output end of the first ejector is connected to the first input end of the second ejector, the first output end of the compressor is connected to the second input end of the second ejector, the output end of the second ejector is connected to the input end of the second gas-liquid separator, the gas phase output end of the second gas-liquid separator is connected to the output end of the first ejector, the liquid phase output end of the second gas-liquid separator is connected to the input end of the air-cooling system, and the output end of the air-cooling system is connected to the user end.

[0018] Furthermore, the supercritical medium refrigeration system also includes an expansion valve, the liquid phase output end of the second gas-liquid separator is connected to the input end of the expansion valve, and the output end of the expansion valve is connected to the input end of the air-cooling system.

[0019] Furthermore, the combined heat and power system includes a water supply system, a heat exchanger, and a turbine. The energy storage medium output end of the first gas-liquid separator is connected to the energy storage medium input end of the heat exchanger. The energy storage medium output end of the heat exchanger is connected to the energy storage medium input end of the cold storage system. The water working fluid input end of the heat exchanger is connected to the water supply system. The water working fluid output end of the heat exchanger is connected to the user end. The steam output end of the heat exchanger is connected to the input end of the turbine. The electrical energy output end of the turbine is connected to the user end.

[0020] Furthermore, the clean energy utilized by the clean energy utilization system is any one or more of solar thermal, photovoltaic, thermal power, and wind power.

[0021] Furthermore, the clean energy utilization system includes a heat exchange system, which employs any one or more of the following: concentrating solar collector tower, trough collector, dish collector, linear Fresnel collector, high-power electric heater, industrial waste heat collector, and industrial steam heat exchanger.

[0022] Furthermore, the supercritical medium is supercritical CO2, and the energy storage medium is molten salt.

[0023] Furthermore, the pressure range of the supercritical CO2 is 6 MPa to 30 MPa.

[0024] Furthermore, the molten salt is one or more of solar salt, Hitec salt, HitecXL salt, chloride salt, and carbonate salt.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. This utility model proposes a multi-energy combined heat and power system based on a transcritical cycle. It utilizes the concept of "supercritical medium (such as supercritical CO2) for cooling - energy storage medium (such as molten salt) for heating - supercritical medium (such as supercritical CO2) and high-temperature energy storage medium (such as high-temperature molten salt) for power supply" to achieve combined cooling, heating, and power generation. In winter, the system heats the energy storage medium with clean energy (e.g., by absorbing solar energy to heat molten salt, and / or by using clean energy sources such as surplus electricity and / or wind power to drive electric heaters to heat molten salt), achieving district heating and power generation. In summer, the system uses a transcritical cycle of supercritical medium (such as supercritical CO2) for district cooling, while the energy storage medium (such as molten salt) can also store energy and generate power using clean energy (e.g., by absorbing solar energy to heat molten salt, and / or by using clean energy sources such as surplus electricity and / or wind power to drive electric heaters to heat molten salt). This coupling method achieves complementary advantages between different energy systems, improving energy utilization efficiency and system flexibility. This multi-functional integrated design meets users' diverse energy needs in different seasons, realizes combined cooling, heating and power supply, and improves the system's practicality and economy.

[0027] 2. This invention employs a dual thermal energy storage strategy, coupling a supercritical medium (such as supercritical CO2) with an energy storage medium (such as molten salt). The supercritical medium (such as supercritical CO2) serves as a thermal energy storage medium, converting 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. Compared to traditional energy storage systems, this strategy significantly improves the energy storage efficiency. Simultaneously, the high specific heat capacity of the molten salt medium optimizes the energy storage efficiency of the supercritical CO2 power generation system. Furthermore, supercritical CO2 can also function as a heat transfer medium. Its density is close to that of a liquid, while its viscosity and diffusion coefficient are close to those of a gas. This accelerates the heat absorption and release rates of the molten salt medium, enabling efficient heat transfer in the system's main thermodynamic processes and rapid response to grid peak-shaving demands, thus enhancing the efficiency and versatility of the energy storage system.

[0028] 3. This utility model employs a coupled energy storage medium (such as molten salt) thermal storage system and a supercritical medium (such as supercritical CO2) circulation system, achieving efficient energy utilization and multifunctional integration, thus improving the system's integration level. The supercritical medium (such as supercritical CO2) circulation system and the energy storage medium (such as molten salt) thermal storage have good coupling properties, allowing for high integration to achieve modular, mobile, and maintenance-free power plants. This is highly competitive for distributed generation and waste heat power generation applications. These advantages can completely compensate for the disadvantage of high prices of early unit equipment, ultimately reducing the cost of power generation.

[0029] 4. This invention employs a strategy of adding supercritical CO2 to low-temperature molten salt. Supercritical CO2 can be used as an auxiliary solvent, utilizing its solvation effect to increase the overall fluidity of the molten salt and lower its freezing point. This strategy effectively prevents the molten salt in this system from solidifying and freezing and clogging pipes in the low-temperature region, providing a new approach to preventing molten salt solidification. 5. This invention uses renewable energy sources such as solar and wind power as the primary energy source, reducing dependence on traditional fossil fuels and lowering greenhouse gas emissions. Simultaneously, the supercritical CO2 circulation system has low emissions, further reducing environmental impact. Carbon dioxide, as a natural working fluid, is non-toxic, flame-retardant, environmentally friendly, easy to purify, and inexpensive, making it a highly promising circulating working fluid. Attached Figure Description

[0030] Other features, objects, and advantages of this invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0031] Figure 1 A schematic diagram of a multi-energy supply system based on transcritical cycle provided for an embodiment of this utility model;

[0032] Figure 2 A bar chart showing the exothermic peak value of solar salt under different CO2 environments in an operation method of a multi-energy supply system based on a transcritical cycle provided for an embodiment of this utility model.

[0033] Figure 3 A schematic diagram of the summer operation structure of a multi-energy supply system based on transcritical cycle provided for an embodiment of this utility model;

[0034] Figure 4 This is a schematic diagram of the winter operation structure of a multi-energy supply system based on transcritical cycle, provided for an embodiment of this utility model.

[0035] In the picture:

[0036] 1. Low-temperature mixture storage tank; 2. Electrically controlled valve; 3. High-temperature mixture storage tank; 4. First gas-liquid separator; 5. Pressure detector; 6. Compressor; 7. Second ejector; 8. Second gas-liquid separator; 9. Expansion valve; 10. Air-cooled system; 11. First ejector; 12. High-pressure turbine; 13. Turbine; 14. Heat exchanger. Detailed Implementation

[0037] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0038] Example:

[0039] like Figure 1 As shown, this embodiment provides a multi-energy combined supply system based on transcritical cycle, characterized in that it includes a clean energy utilization system, an energy storage system, a supercritical medium power generation system, a supercritical medium refrigeration system, a combined heat and power system, and a control system. The clean energy utilization system, the energy storage system, the supercritical medium power generation system, the supercritical medium refrigeration system, and the combined heat and power system are electrically connected to the control system.

[0040] Energy storage systems include thermal storage systems and cold storage systems;

[0041] The supercritical medium power generation system includes a first gas-liquid separator 4, a pressure detector 5, a compressor 6, and a high-pressure turbine 12;

[0042] The supercritical medium refrigeration system includes a first ejector 11, a second ejector 7, a second gas-liquid separator 8, an expansion valve 9, and an air-cooling system 10;

[0043] The combined heat and power system includes a water supply system (not shown in the figure), a heat exchanger 14, and a turbine 13;

[0044] The output end of the cold storage system is connected to the input end of the clean energy utilization system, and the output end of the clean energy utilization system is connected to the input end of the heat storage system, so that the low-temperature mixed working fluid stored in the cold storage system is heated by heat exchange in the clean energy utilization system to obtain a high-temperature mixed working fluid and stored in the heat storage system.

[0045] The output end of the thermal storage system is connected to the input end of the first gas-liquid separator 4, so that the first gas-liquid separator 4 can separate the high-temperature mixed working fluid into a high-temperature energy storage medium and a high-temperature supercritical medium.

[0046] The energy storage medium output end of the first gas-liquid separator 4 is connected to the energy storage medium input end of the heat exchanger 14. The energy storage medium output end of the heat exchanger 14 is connected to the energy storage medium input end of the cold storage system. The water working fluid input end of the heat exchanger 14 is connected to the water supply system. The water working fluid output end of the heat exchanger 14 is connected to the user end. The steam output end of the heat exchanger 14 is connected to the input end of the turbine 13. The electrical energy output end of the turbine 13 is connected to the user end. The high-temperature energy storage medium exchanges heat with the water working fluid provided by the water supply system in the heat exchanger 14 to obtain a low-temperature energy storage medium, a high-temperature water working fluid, and high-temperature steam. The low-temperature energy storage medium is transported to the cold storage system for storage to realize the recycling of the energy storage medium. The high-temperature water working fluid is used to provide heat energy to the user end. The high-temperature steam enters the turbine 13 to cause the turbine 13 to do work, thereby converting mechanical energy into electrical energy for the power supply to the user end. It should be noted that the ratio of heat energy and electrical energy output of the cogeneration system can be selected according to the actual application scenario.

[0047] The supercritical medium output end of the first gas-liquid separator 4 is connected to the input end of the pressure detector 5. The pressure detector 5 is used to monitor the pressure of the supercritical medium output by the first gas-liquid separator 4, so that the control system can adjust the multi-energy supply system according to the monitoring results. The output end of the pressure detector 5 is connected to the first input end of the compressor 6, so that the supercritical medium is pressurized under the action of the compressor 6. The first output end of the compressor 6 is connected to the input end of the high-pressure turbine 12, so that the supercritical medium enters the high-pressure turbine 12 to do work and generate electrical energy. The electrical energy output end of the high-pressure turbine 12 is connected to the user end, so as to supply the user end with the electrical energy generated by the supercritical medium entering the high-pressure turbine 12 to do work. The second output end of the compressor 6 is connected to the supercritical medium input end of the cold storage system to realize the recycling of the supercritical medium. It should be noted that the ratio of supercritical medium output from the first output end and the second output end of the compressor 6 can be selected according to the actual application scenario.

[0048] The supercritical medium output end of the high-pressure turbine 12 is connected to the input end of the first ejector 11, and the return end of the first ejector 11 is connected to the second input end of the compressor 6 to achieve the recycling of the supercritical medium. The output end of the first ejector 11 is connected to the first input end of the second ejector 7, and the first output end of the compressor 6 is connected to the second input end of the second ejector 7. The first ejector 11 achieves the first-stage injection of the supercritical medium, and the second ejector 7 achieves the second-stage injection of the supercritical medium. It is worth noting that the mixed supercritical medium in the second ejector 7 is composed of a mixture of low-pressure supercritical medium from the first ejector 11 and high-pressure supercritical medium from the compressor 6, which helps to ensure injection efficiency and injection stability, reduce throttling losses, and improve energy utilization. It should be noted that the first ejector 11 can be selected for return according to the actual application scenario. The ratio of supercritical medium delivery at the end and output end is selected by the second ejector 7, which can select the ratio of low-pressure supercritical medium from the first ejector 11 to high-pressure supercritical medium from the compressor 6 according to the actual application scenario. The output end of the second ejector 7 is connected to the input end of the second gas-liquid separator 8, and the gas phase output end of the second gas-liquid separator 8 is connected to the output end of the first ejector 11, so that the gas phase supercritical medium participates in the injection process again to realize the recycling of supercritical medium. The liquid phase output end of the second gas-liquid separator 8 is connected to the input end of the expansion valve 9, and the output end of the expansion valve 9 is connected to the input end of the air-cooling system 10, so that the liquid phase supercritical medium is depressurized under the action of the expansion valve 9 and evaporates and absorbs heat in the air-cooling system to achieve phase change and achieve refrigeration effect. The output end of the air-cooling system 10 is connected to the user end to supply the cold energy generated by the supercritical medium refrigeration system to the user end.

[0049] Among them, the clean energy utilization system utilizes any one or more of the following clean energy sources: solar thermal, photovoltaic, thermal power, and wind power; the clean energy utilization system includes a heat exchange system, which adopts any one or more of the following heat exchange systems: concentrating solar collector tower, trough collector, dish collector, linear Fresnel collector, high-power electric heater, industrial waste heat collector, and industrial steam heat exchanger.

[0050] The supercritical medium is supercritical CO2, and the energy storage medium is molten salt; the pressure range of supercritical CO2 is 6MPa to 30MPa; the molten salt is one or more of solar salt, Hitec salt, HitecXL salt, chloride salt, and carbonate salt.

[0051] Specifically, electrically controlled valves electrically connected to the control system are installed at the energy storage medium input end of the cold storage system, the output end of the cold storage system, the input end of the heat storage system, the output end of the heat storage system, the first output end of the compressor 6, the second output end of the compressor 6, the output end of the high-pressure turbine 12, the return end of the first ejector 11, and the output end of the second ejector 7. The control system can regulate each electrically controlled valve. Among them, the electrically controlled valve installed at the first output end of the compressor 6 realizes the flow split connection between the first output end of the compressor 6 and the input end of the high-pressure turbine 12 and the second input end of the second ejector 7.

[0052] like Figure 1 As shown, in a specific embodiment, this multi-energy system based on transcritical cycle includes a clean energy utilization system, an energy storage system, a supercritical CO2 power generation system, a supercritical CO2 refrigeration system, a cogeneration system, and a control system. The clean energy utilization system, the energy storage system, the supercritical CO2 power generation system, the supercritical CO2 refrigeration system, and the cogeneration system are electrically connected to the control system.

[0053] The energy storage system includes a thermal storage system and a cold storage system; the thermal storage system is configured as a high-temperature mixture storage tank 3, and the cold storage system is configured as a low-temperature mixture storage tank 1.

[0054] The supercritical CO2 power generation system includes a first gas-liquid separator 4, a pressure detector 5, a compressor 6, and a high-pressure turbine 12;

[0055] The supercritical CO2 refrigeration system includes a first ejector 11, a second ejector 7, a second gas-liquid separator 8, an expansion valve 9, and an air-cooling system 10;

[0056] The combined heat and power system includes a water supply system (not shown in the figure), a heat exchanger 14, and a turbine 13;

[0057] The output end of the low-temperature mixture storage tank 1 is connected to the input end of the clean energy utilization system via an electrically controlled valve 2. The output end of the clean energy utilization system is connected to the input end of the high-temperature mixture storage tank 3 via an electrically controlled valve 2, so that the low-temperature mixture working fluid stored in the low-temperature mixture storage tank 1 is heated by heat exchange in the clean energy utilization system to obtain a high-temperature mixture working fluid, which is then stored in the high-temperature mixture storage tank 3.

[0058] The output end of the high-temperature mixture storage tank 3 is connected to the input end of the first gas-liquid separator 4 via an electrically controlled valve 2, so that the first gas-liquid separator 4 can separate the high-temperature mixed working fluid into high-temperature molten salt and high-temperature supercritical CO2.

[0059] The molten salt output end of the first gas-liquid separator 4 is connected to the molten salt input end of the heat exchanger 14. The molten salt output end of the heat exchanger 14 is connected to the molten salt input end of the low-temperature mixture storage tank 1 via the electrically controlled valve 2. The water working fluid input end of the heat exchanger 14 is connected to the water supply system, the water working fluid output end of the heat exchanger 14 is connected to the user end, the steam output end of the heat exchanger 14 is connected to the input end of the turbine 13, and the power output end of the turbine 13 is connected to the user end. The high-temperature molten salt exchanges heat with the water working fluid provided by the water supply system in the heat exchanger 14 to obtain low-temperature molten salt, high-temperature water working fluid, and high-temperature steam. The low-temperature molten salt is transported to the low-temperature mixture storage tank 1 for storage to realize the recycling of molten salt. The high-temperature water working fluid is used to provide heat energy to the user end. The high-temperature steam enters the turbine 13 to cause the turbine 13 to do work, thereby converting mechanical energy into electrical energy for the power supply to the user end. It should be noted that the output ratio of heat energy and electrical energy of the cogeneration system can be adjusted by the control system according to the actual application scenario.

[0060] The supercritical CO2 output terminal of the first gas-liquid separator 4 is connected to the input terminal of the pressure detector 5. The pressure detector 5 is used to monitor the pressure of the supercritical CO2 output by the first gas-liquid separator 4, so that the control system can adjust the multi-energy supply system according to the monitoring results. The output terminal of the pressure detector 5 is connected to the first input terminal of the compressor 6, so that the supercritical CO2 is pressurized under the action of the compressor 6. The first output terminal of the compressor 6 is divided into two branches through the electronically controlled valve 2. One branch is connected to the input terminal of the high-pressure turbine 12, so that the supercritical CO2 enters the high-pressure turbine 12 to do work and generate electrical energy. The electrical energy output terminal of the high-pressure turbine 12 is connected to the user terminal to supply the electrical energy generated by the supercritical CO2 entering the high-pressure turbine 12 to the user terminal. The second output terminal of the compressor 6 is connected to the supercritical CO2 input terminal of the cryogenic mixture storage tank 1 through the electronically controlled valve 2 to realize the recycling of supercritical CO2. It should be noted that the ratio of supercritical CO2 output from the first and second output terminals of the compressor 6 can be adjusted by the control system according to the actual application scenario.

[0061] The supercritical CO2 output of the high-pressure turbine 12 is connected to the input of the first ejector 11 via an electrically controlled valve 2. The return end of the first ejector 11 is connected to the second input of the compressor 6 via the electrically controlled valve 2 to achieve the recycling of supercritical CO2. The output of the first ejector 11 is connected to the first input of the second ejector 7, and another branch of the first output of the compressor 6 is connected to the second input of the second ejector 7. The first ejector 11 achieves the first-stage injection of supercritical CO2, and the second ejector 7 achieves the second-stage injection of supercritical CO2. It is worth noting that the mixed supercritical CO2 in the second ejector 7 is composed of low-pressure supercritical CO2 from the first ejector 11 and high-pressure supercritical CO2 from the compressor 6, which helps to ensure injection efficiency and stability, reduce throttling losses, and improve energy utilization. It should be noted that the first injection can be adjusted by the control system according to the actual application scenario. The ratio of supercritical CO2 delivery at the return end and output end of the injector 11 can also be adjusted by the control system according to the actual application scenario, based on the ratio of low-pressure supercritical CO2 from the first injector 11 and high-pressure supercritical CO2 from the compressor 6 in the second injector 7. The output end of the second injector 7 is connected to the input end of the second gas-liquid separator 8 via the electronically controlled valve 2. The gas phase output end of the second gas-liquid separator 8 is connected to the output end of the first injector 11, so that the gas phase supercritical CO2 participates in the injection process again, realizing the recycling of supercritical CO2. The liquid phase output end of the second gas-liquid separator 8 is connected to the input end of the expansion valve 9. The output end of the expansion valve 9 is connected to the input end of the air-cooling system 10, so that the liquid phase supercritical CO2 is depressurized under the action of the expansion valve 9 and evaporates and absorbs heat in the air-cooling system, realizing phase change and achieving a cooling effect. The output end of the air-cooling system 10 is connected to the user end to supply the cold energy generated by the supercritical CO2 refrigeration system to the user end.

[0062] The operation method of this multi-energy system based on transcritical cycle includes the following stages:

[0063] 1. Heat collection and storage stage:

[0064] When surplus electrical energy is stored through solar thermal storage, grid storage, or other clean energy sources, the mixture of supercritical CO2 and molten salt in the cryogenic mixture storage tank 1 enters the heat exchange system. The cryogenic molten salt in the cryogenic mixture storage tank 1 can flow into the heat exchange system more quickly under the pressure of supercritical CO2. The heat exchange system uses the input of clean energy to heat the mixture working medium, and the high-temperature mixture working medium after absorbing heat is stored in the high-temperature mixture storage tank 3.

[0065] Clean energy sources can be selected based on actual application scenarios, such as solar thermal, photovoltaic, thermal power, and wind power.

[0066] The pressure of supercritical CO2 can be selected from 6MPa to 30MPa depending on the specific application scenario.

[0067] Among them, molten salt can be selected from one or more of the following: solar salt, Hitec salt, HitecXL salt, chloride salt, and carbonate salt, depending on the specific application scenario.

[0068] The heat exchange system can be selected from any one or more of the following: concentrating solar collector tower, trough collector, dish collector, linear Fresnel collector, high-power electric heater, industrial waste heat collector, and industrial steam heat exchanger.

[0069] 2. Supercritical CO2 power generation stage:

[0070] When electrical energy output is required, the high-temperature mixture of molten salt and supercritical CO2 first enters the first gas-liquid separator 4 to separate the supercritical CO2 and molten salt. The outlet of the first gas-liquid separator 4 is divided into two paths: one path connects to the supercritical CO2 separation side, and the other path connects to the molten salt separation side. The supercritical CO2 separation side is first connected to the pressure detector 5 to monitor the initial pressure of the supercritical CO2. When the pressure measurement value monitored by the pressure detector 5 exceeds the set value (safe pressure value), the electronically controlled valve 2 is switched. The high-pressure liquid supercritical CO2 formed after compression by the compressor 6 enters the high-pressure turbine 12 through the electronically controlled valve 2 to generate electricity. At the same time, the high-pressure turbine 12 outputs low-pressure liquid supercritical CO2 and enters the first ejector 11 (first-stage ejector) for injection.

[0071] 3. Supercritical CO2 refrigeration stage:

[0072] The high-pressure liquid supercritical CO2 formed after compression by compressor 6 can be controlled by electronic valve 2 to enter the second ejector 7 (secondary injection). The use of the ejector can further improve the stability and operating efficiency of the system by optimizing the internal pressure distribution and flow distribution. After injection, it is transported to the air-cooling system 10 for cooling via the second gas-liquid separator 8. In addition, the low-temperature, low-pressure supercritical CO2 injected by the first ejector 11 is injected into the interior of the second ejector 7 and mixed evenly with the liquid supercritical CO2. Thus, the first ejector 11 and the second ejector 7 achieve high and low pressure secondary injection, which can ensure injection efficiency and injection stability, reduce throttling losses, and improve energy utilization. This mixing heat exchange method can effectively improve the heat exchange effect of the ejector, thereby improving the performance coefficient of the refrigeration system. Finally, the cooled supercritical CO2 flows back to compressor 6. If further cooling is required, it can directly enter the next supercritical CO2 refrigeration cycle. If refrigeration is completed, it can be returned to the low-temperature mixture storage tank 1 for storage.

[0073] 4. Combined Heat and Power (CHP) Stage:

[0074] The high-temperature molten salt is connected to the heat exchanger 14 on the separation side. The high-temperature molten salt is pumped to the heat exchanger 14 and exchanges heat with water or other working fluids to generate steam and / or hot water. The steam enters the turbine 13 to generate electricity, and the hot water is directly supplied to users for heating. The molten salt has a wide operating temperature range, which can realize hot water heating at 90℃, medium and low temperature industrial steam supply at 180~360℃, and high temperature steam supply above 500℃.

[0075] 5. Storage stage:

[0076] After the molten salt completes heat exchange, it enters the low-temperature mixture storage tank 1 for storage. Then, supercritical CO2 at 6MPa to 30MPa is introduced to reduce the viscosity of the low-temperature molten salt and maintain its fluidity by utilizing the solvation effect of supercritical CO2. The low-temperature molten salt can be kept warm by an electric heater or by using a technology that couples supercritical CO2 with an electric heater.

[0077] During the experimental phase, analysis and testing were conducted using a high-pressure differential scanning calorimeter. The specific experimental procedures are as follows:

[0078] Thermal analysis experiments were conducted on solar salt samples using a high-pressure differential scanning calorimeter (HP-DSC); the analytical instrument was a Netzsch DSC204HP high-pressure differential scanning calorimeter from Germany.

[0079] Weigh 10 mg of sample (error less than 0.01 mg), and set the heating rate to 15 °C / min. For the test under normal pressure conditions, select 0.1 MPa CO2 as the protective gas (0.1 MPa is approximately considered as normal pressure in this embodiment). For the test under 8 MPa CO2 conditions, adjust the CO2 pressure to 8 MPa and the initial temperature to 40 °C before the experiment begins.

[0080] Non-isothermal tests were conducted on solar salt under different CO2 pressure environments (8 MPa CO2 and 0.1 MPa CO2) using a high-pressure differential scanning calorimeter (0.1 MPa CO2 was used as the protective gas). Figure 2 As shown, the onset, peak, and termination points of the exothermic peak of solar salt under conventional conditions (0.1 MPa CO2) are 183.9℃, 221.7℃, and 268.2℃, respectively; meanwhile, the onset, peak, and termination points of the exothermic peak of solar salt under 8 MPa CO2 conditions are 175.2℃, 206.7℃, and 248.9℃, respectively. These results indicate that the freezing point or melting point of solar salt decreases by approximately 16℃ under 8 MPa supercritical CO2 conditions.

[0081] It should be noted that the operation mode of the multi-energy supply system based on transcritical cycle provided in this embodiment can be the same or different in summer and winter. The following explanation illustrates the difference between summer and winter operation modes:

[0082] Because of abundant sunlight in summer and the large demand for cooling and electricity from users, therefore, Figure 3 As shown, the multi-energy combined heat and power system based on transcritical cycle provided in this embodiment operates as follows in summer: the working fluid of 8MPa supercritical CO2 and solar salt in the low-temperature mixture storage tank 1 enters the concentrating solar collector for heat exchange; the low-temperature molten salt in the low-temperature mixture storage tank 1 can flow into the concentrating solar collector more quickly under the pressure of supercritical CO2; the high-temperature mixture working fluid after heat absorption is stored in the high-temperature mixture storage tank 3. The working fluid of high-temperature molten salt and supercritical CO2 first enters the first gas-liquid separator 4 to separate the supercritical CO2 and high-temperature molten salt; the outlet of the first gas-liquid separator 4 is divided into two paths, one connected to the supercritical CO2 separation side and the other connected to the molten salt separation side; the supercritical CO2 separation side is first connected to the pressure detector 5 to monitor the initial supercritical CO2 pressure; the high-pressure liquid phase supercritical CO2 formed after compression by the compressor 6 is controlled by the electronically controlled valve 2 to enter the high-pressure turbine 12 to generate electricity for users. Simultaneously, the high-pressure turbine 12 outputs low-pressure liquid supercritical CO2, which enters the first ejector 11 (primary ejector) for injection. The high-pressure liquid supercritical CO2 formed after compression by the compressor 6 can be controlled by the electronically controlled valve 2 to enter the second ejector 7 (secondary ejector). After injection, it is transported to the air-cooling system 10 via the second gas-liquid separator 8 for cooling. Furthermore, the low-temperature, low-pressure supercritical CO2 injected by the first ejector 11 is drawn into the second ejector 7, where it mixes evenly with the liquid supercritical CO2, thus achieving high- and low-pressure two-stage injection by the first ejector 11 and the second ejector 7. Finally, the cooled supercritical CO2 flows back to the compressor 6. If further cooling is needed, it can directly enter the next supercritical CO2 refrigeration cycle; if refrigeration is finished, it can flow back to the low-temperature mixture storage tank 1 for storage. A heat exchanger 14 is connected to the high-temperature molten salt separation side. The high-temperature molten salt is pumped to the heat exchanger 14, where it exchanges heat with water to generate steam, which enters the turbine 13 to generate electricity for the user.

[0083] Because heating demand increases significantly in winter, therefore, Figure 4As shown, the multi-energy combined heat and power system based on transcritical cycle provided in this embodiment operates as follows in winter: the working fluid of 8MPa supercritical CO2 and solar salt in the low-temperature mixture storage tank 1 enters the high-power electric heater for heating; clean energy such as abandoned electricity or wind power is used to drive the electric heater; the low-temperature molten salt in the low-temperature mixture storage tank 1 can flow into the high-power electric heating system more quickly under the pressure of supercritical CO2; the high-temperature mixture working fluid after heat absorption is stored in the high-temperature mixture storage tank 3. The working fluid of high-temperature molten salt and supercritical CO2 first enters the first gas-liquid separator 4 to separate the supercritical CO2 and high-temperature molten salt; the outlet of the first gas-liquid separator 4 is divided into two paths, one connected to the supercritical CO2 separation side and the other connected to the molten salt separation side; the supercritical CO2 separation side is first connected to the pressure detector 5 to monitor the initial supercritical CO2 pressure; the high-pressure liquid phase supercritical CO2 formed after compression by the compressor 6 enters the high-pressure turbine 12 through the electrically controlled valve to generate electricity for users. Supercritical CO2 is refluxed to the cryogenic mixture storage tank 1 for storage. The high-temperature molten salt separation side is connected to the heat exchanger 14. The high-temperature molten salt is pumped to the heat exchanger 14 to exchange heat with water, generating steam and hot water. The high-temperature steam enters the turbine 13 to generate electricity to the user, and the hot water is directly connected to the user side for heating.

[0084] Molten salt and supercritical CO2 are considered among the most promising combined heat exchange media for third-generation solar thermal power generation. This embodiment combines supercritical CO2 technology with molten salt thermal storage technology to construct a comprehensive energy service system integrating efficient energy conversion, flexible energy storage and regulation, and multifunctional cooling, heating, and power supply, thereby achieving efficient energy utilization and sustainable development. Furthermore, this system can effectively utilize the solvation effect of supercritical CO2 to reduce the viscosity and increase the fluidity of the molten salt system, effectively preventing molten salt freezing problems.

[0085] The specific embodiments of this utility model have been described above. It should be understood that this utility model is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the substantive content of this utility model. Unless otherwise specified, the embodiments and features of this utility model can be arbitrarily combined with each other.

Claims

1. A multi-energy supply system based on transcritical cycle, characterized in that, It includes a clean energy utilization system, an energy storage system, a supercritical medium power generation system, a supercritical medium refrigeration system, a combined heat and power system, and a control system. The clean energy utilization system, the energy storage system, the supercritical medium power generation system, the supercritical medium refrigeration system, and the combined heat and power system are all electrically connected to the control system. The energy storage system includes a thermal storage system and a cold storage system. The output end of the cold storage system is connected to the input end of the clean energy utilization system, and the output end of the clean energy utilization system is connected to the input end of the thermal storage system, so that the low-temperature mixed working fluid stored in the cold storage system is heated by the clean energy utilization system to obtain a high-temperature mixed working fluid, which is then stored in the thermal storage system. The supercritical medium power generation system includes a first gas-liquid separator (4), a compressor (6), and a high-pressure turbine (12); the output end of the thermal energy storage system is connected to the input end of the first gas-liquid separator (4), and the energy storage medium output end of the first gas-liquid separator (4) is connected to the input end of the cogeneration system, so that the high-temperature energy storage medium enters the cogeneration system to generate electrical energy and / or thermal energy. The supercritical medium output end of the first gas-liquid separator (4) is connected to the first input end of the compressor (6), so that the supercritical medium in the... The compressor (6) pressurizes the supercritical medium. The first output end of the compressor (6) is connected to the input end of the high-pressure turbine (12) so that the supercritical medium enters the high-pressure turbine (12) to do work and generate electrical energy. The electrical energy output end of the high-pressure turbine (12) is connected to the user end to supply the user end with the electrical energy generated by the supercritical medium entering the high-pressure turbine (12) to do work. The second output end of the compressor (6) is connected to the supercritical medium input end of the cold storage system to realize the recycling of the supercritical medium. The supercritical medium output end of the high-pressure turbine (12) is connected to the first input end of the supercritical medium refrigeration system, and the first output end of the compressor (6) is also connected to the second input end of the supercritical medium refrigeration system, so that the supercritical medium output by the high-pressure turbine (12) and / or the compressor (6) enters the supercritical medium refrigeration system to achieve refrigeration. The return end of the supercritical medium refrigeration system is connected to the second input end of the compressor (6) to realize the recycling of the supercritical medium. The output end of the supercritical medium refrigeration system is connected to the user end to supply the cold energy generated by the supercritical medium refrigeration system to the user end. The energy output end of the cogeneration system is connected to the user end, and is used to supply the electrical energy and / or heat energy generated by the cogeneration system to the user end. The energy storage medium output end of the cogeneration system is connected to the energy storage medium input end of the cold storage system, and is used to return the low-temperature energy storage medium obtained by the high-temperature energy storage medium through heat exchange in the cogeneration system to the cold storage system, so as to realize the recycling of the energy storage medium.

2. The multi-energy supply system based on transcritical cycle according to claim 1, characterized in that, The supercritical medium power generation system also includes a pressure detector (5). The supercritical medium output end of the first gas-liquid separator (4) is connected to the input end of the pressure detector (5). The output end of the pressure detector (5) is connected to the first input end of the compressor (6). The pressure detector (5) is used to monitor the pressure of the supercritical medium output by the first gas-liquid separator (4), so that the control system can regulate the multi-energy power generation system according to the monitoring results.

3. A multi-energy supply system based on a transcritical cycle according to claim 1, characterized in that, The supercritical medium refrigeration system includes a first ejector (11), a second ejector (7), a second gas-liquid separator (8), and an air-cooling system (10). The supercritical medium output end of the high-pressure turbine (12) is connected to the input end of the first ejector (11), the return end of the first ejector (11) is connected to the second input end of the compressor (6), the output end of the first ejector (11) is connected to the first input end of the second ejector (7), the first output end of the compressor (6) is connected to the second input end of the second ejector (7), the output end of the second ejector (7) is connected to the input end of the second gas-liquid separator (8), the gas phase output end of the second gas-liquid separator (8) is connected to the output end of the first ejector (11), the liquid phase output end of the second gas-liquid separator (8) is connected to the input end of the air-cooling system (10), and the output end of the air-cooling system (10) is connected to the user end.

4. A multi-energy supply system based on transcritical cycle according to claim 3, characterized in that, The supercritical medium refrigeration system also includes an expansion valve (9), the liquid phase output end of the second gas-liquid separator (8) is connected to the input end of the expansion valve (9), and the output end of the expansion valve (9) is connected to the input end of the air-cooling system (10).

5. A multi-energy supply system based on transcritical cycle according to claim 1, characterized in that, The combined heat and power system includes a water supply system, a heat exchanger (14), and a turbine (13). The energy storage medium output end of the first gas-liquid separator (4) is connected to the energy storage medium input end of the heat exchanger (14). The energy storage medium output end of the heat exchanger (14) is connected to the energy storage medium input end of the cold storage system. The water working medium input end of the heat exchanger (14) is connected to the water supply system. The water working medium output end of the heat exchanger (14) is connected to the user end. The steam output end of the heat exchanger (14) is connected to the input end of the turbine (13). The electrical energy output end of the turbine (13) is connected to the user end.

6. A multi-energy supply system based on transcritical cycle according to claim 1, characterized in that, The clean energy utilization system utilizes any one or more of the following: solar thermal, photovoltaic, thermal power, and wind power.

7. A multi-energy supply system based on a transcritical cycle according to claim 6, characterized in that, The clean energy utilization system includes a heat exchange system, which employs any one or more of the following: concentrating solar collector tower, trough collector, dish collector, linear Fresnel collector, high-power electric heater, industrial waste heat collector, and industrial steam heat exchanger.

8. A multi-energy supply system based on a transcritical cycle according to any one of claims 1 to 7, characterized in that, The supercritical medium is supercritical CO2, and the energy storage medium is molten salt.

9. A multi-energy supply system based on a transcritical cycle according to claim 8, characterized in that, The pressure range of the supercritical CO2 is 6 MPa to 30 MPa.

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