Carbon dioxide cycle photo-thermal power generation system and method

Abstract

This invention discloses a carbon dioxide cycle solar thermal power generation system and method, including a thermal storage system, a CO2 power generation system, a CO2 heat pump system, and a cold storage system. The CO2 power generation system includes a CO2 turbine, a high-temperature regenerator, a low-temperature regenerator, a precooler, a main compressor, and a re-compressor. The high-temperature outlet of the CO2 side of the molten salt heat exchanger is connected to the inlet of the CO2 turbine. The outlet of the CO2 turbine is connected to the high-temperature and low-temperature regenerators. The low-pressure, low-temperature outlet of the low-temperature regenerator is divided into two paths: one path is connected to the inlet of the re-compressor, and the other path is connected to the thermal storage system via the precooler, re-compressor, and high-temperature regenerator. The precooler is also connected to the cold storage system. This invention significantly reduces equipment investment costs and increases system economy. The CO2 cycle solar thermal power generation system can utilize the cold energy stored in the heat pump system to cool the low-temperature end to an even lower temperature, improving the overall efficiency of the power generation system.

Description

Technical Field

[0001] This invention relates to a power generation system, specifically to a carbon dioxide cycle solar thermal power generation system and method. Background Technology

[0002] Against the backdrop of energy scarcity and environmental crisis, improving energy efficiency is receiving increasing attention. Solar energy is an inexhaustible and clean energy source. Currently, solar photovoltaic (PV) technology is relatively mature and widely applied, but energy storage remains a challenge. While PV power generation systems struggle with energy storage, the most mature PV energy storage solution is still battery storage. However, battery storage remains too expensive and poses risks such as fires. For large-scale energy storage needs at power plant levels, various types of battery storage are currently difficult to promote. Meanwhile, solar thermal power generation is gaining increasing attention due to its high theoretical thermal efficiency at high temperatures and the potential for relatively inexpensive thermal storage to address the uneven temporal distribution of solar energy. Furthermore, electrothermal energy storage is a relatively efficient energy storage method, with CO2 heat pump electrothermal energy storage technology being one of the most efficient.

[0003] However, solar thermal power generation has always faced difficulties in widespread adoption due to its high cost. On the other hand, photovoltaic (PV) power generation has seen its price drop significantly after years of development, and the government is gradually reducing its electricity price subsidies. If solar thermal power generation could be combined with other new energy sources, utilizing some inexpensive and technologically mature PV and wind power systems, and then integrating thermal energy storage and thermal power generation systems as a regulating and supplementary power supply system for PV power generation, it would be possible to maintain relatively low investment costs for the power generation system while achieving stable power output. However, both solar thermal power generation and electrothermal energy storage are relatively expensive, and cost reduction is a long-term goal for these technologies. Meanwhile, CO2 cycle solar thermal power generation systems and CO2 electrothermal energy storage systems require corresponding CO2 regenerators, precoolers, compressors, turbines, etc. Combining the two and sharing some equipment could significantly reduce investment costs.

[0004] The "PV+" model is characterized by large-scale PV and small-scale solar thermal power generation. This means maximizing the low cost of PV by using large-area PV to lower the overall price of solar power generation. The low unit price of PV power allows for the storage of heat in molten salt heaters within electric heaters, significantly reducing the mirror field area and thus lowering the cost of the solar thermal power generation system. Simultaneously, it leverages the energy storage and peak-shaving capabilities of the solar thermal system. Since PV systems themselves face challenges in energy storage, while solar thermal power generation systems offer inexpensive energy storage, using a low-cost solar thermal system to store energy for PV systems effectively solves the PV energy storage problem. Summary of the Invention

[0005] In order to overcome the problems existing in the prior art, the purpose of this invention is to provide a carbon dioxide cycle solar thermal power generation system and method, which realizes energy storage of solar power generation while maintaining a low investment cost.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A carbon dioxide cycle solar thermal power generation system includes a thermal storage system, a CO2 power generation system, a CO2 heat pump system, and a cold storage system;

[0008] The heat pump system includes an electric heater, a low-temperature expander, and a high-temperature compressor. The CO2 side outlet of the electric heater and the low-temperature expander are connected to the CO2 power generation system, and the high-temperature compressor is connected to the electric heater.

[0009] The CO2 power generation system includes a CO2 turbine, a high-temperature regenerator, a low-temperature regenerator, a precooler, a main compressor, and a re-compressor. The high-temperature outlet on the CO2 side of the molten salt heat exchanger is connected to the inlet of the CO2 turbine. The outlet of the CO2 turbine is connected to the low-pressure high-temperature inlet of the high-temperature regenerator. The low-pressure low-temperature outlet of the high-temperature regenerator is connected to the low-pressure high-temperature inlet of the low-temperature regenerator. The low-pressure low-temperature outlet of the low-temperature regenerator is divided into two paths: one path is connected to the inlet of the re-compressor, and the other path is connected to the high-temperature inlet on the CO2 side of the precooler. The low-temperature outlet on the CO2 side of the precooler and the outlet of the re-compressor merge and are then connected to the high-pressure low-temperature inlet of the high-temperature regenerator. The high-pressure high-temperature outlet of the high-temperature regenerator is connected to the thermal storage system. The precooler is also connected to the cold storage system.

[0010] Furthermore, the thermal storage system includes a solar collector, a high-temperature molten salt tank, a molten salt heat exchanger, and a low-temperature molten salt tank. The outlet of the solar collector is connected to the inlet of the high-temperature molten salt tank, the outlet of the high-temperature molten salt tank is connected to the high-temperature inlet of the molten salt heat exchanger, the low-temperature outlet of the molten salt heat exchanger is connected to the inlet of the low-temperature molten salt tank, and the outlet of the low-temperature molten salt tank is connected to the inlet of the solar collector. The high-pressure, high-temperature outlet of the high-temperature regenerator is connected to the low-temperature inlet of the CO2 side of the molten salt heat exchanger.

[0011] Furthermore, the CO2 side outlet of the electric heater is connected to the high-temperature CO2 side inlet of the molten salt heat exchanger, and the low-temperature CO2 side outlet of the molten salt heat exchanger is connected to the high-pressure, high-temperature side inlet of the high-temperature regenerator.

[0012] Furthermore, the CO2-side low-temperature outlet of the precooler is connected to the inlet of the main compressor, the outlet of the main compressor is connected to the high-pressure low-temperature inlet of the low-temperature regenerator, and the high-pressure high-temperature outlet of the low-temperature regenerator merges with the outlet of the re-compressor and is then connected to the high-pressure low-temperature inlet of the high-temperature regenerator.

[0013] Furthermore, the CO2-side outlet of the electric heater is connected to the high-temperature CO2-side inlet of the molten salt heat exchanger; the low-temperature CO2-side outlet of the molten salt heat exchanger is connected to the high-pressure high-temperature inlet of the high-temperature regenerator; the high-pressure low-temperature outlet of the high-temperature regenerator is connected to the high-pressure high-temperature inlet of the low-temperature regenerator; the high-pressure low-temperature outlet of the low-temperature regenerator is connected to the inlet of the low-temperature expander; the outlet of the low-temperature expander is connected to the low-temperature CO2-side inlet of the precooler; the high-temperature CO2-side outlet of the precooler is connected to the low-pressure low-temperature inlet of the low-temperature regenerator; the low-pressure high-temperature outlet of the low-temperature regenerator is connected to the low-pressure low-temperature inlet of the high-temperature regenerator; the low-pressure high-temperature outlet of the high-temperature regenerator is connected to the inlet of the high-temperature compressor; and the outlet of the high-temperature compressor is connected to the CO2-side inlet of the electric heater.

[0014] Furthermore, the cold storage system includes a low-temperature water storage tank and a high-temperature water storage tank. The low-temperature water storage tank is connected to the low-temperature water inlet of the precooler, and the high-temperature water storage tank is connected to the high-temperature water inlet of the precooler.

[0015] An operation method for a carbon dioxide cycle solar thermal power generation system as described above includes the following steps:

[0016] When the photovoltaic system is at its peak power generation during the day, it enters the energy storage mode, compressing low-pressure CO2 to high-pressure and high-temperature. The high-pressure and high-temperature CO2 enters the CO2 side of the electric heater for further heating, and then enters the CO2 side of the molten salt heat exchanger to release heat. After that, it enters the high-pressure side of the high-temperature regenerator and the low-temperature regenerator in sequence to continue releasing heat. Then, it enters the low-temperature expander to expand and do work. The expanded CO2 working fluid is at a low temperature and enters the CO2 side of the precooler to output cold energy. After absorbing heat in the precooler, it enters the low-pressure side of the low-temperature regenerator and the high-temperature regenerator in sequence to continue absorbing heat. The preheated CO2 enters the high-temperature compressor to be compressed, completing the CO2 heat pump cycle.

[0017] Furthermore, the hot water in the high-temperature storage tank is transported to the water side of the precooler to release heat, and the cold water that absorbs the cold energy returns to the low-temperature storage tank for storage.

[0018] The molten salt in the low-temperature molten salt tank is divided into two paths. One path enters the solar collector to absorb heat from the solar energy. After being heated, it enters the high-temperature molten salt tank for storage. The other path enters the molten salt side of the molten salt heat exchanger to absorb heat from the high-temperature CO2. After being heated, it enters the high-temperature molten salt tank for storage.

[0019] Further, when the local power grid is at the peak electricity consumption period, CO2 enters the molten salt heat exchanger and is heated to a high temperature, then enters the CO2 turbine to do work, and then successively enters the low-pressure side of the high-temperature recuperator and the low-pressure side of the low-temperature recuperator to release heat. Then, a part of the CO2 enters the recompressor and is directly pressurized, and another part of the CO2 enters the pre-cooler and is further cooled, then enters the main compressor and is pressurized, then enters the high-pressure side of the low-temperature recuperator to absorb heat, and then converges with the CO2 at the outlet of the recompressor side and enters the high-pressure side of the high-temperature recuperator to absorb heat, and finally returns to the CO2-side inlet of the molten salt heat exchanger.

[0020] Further, the low-temperature water in the low-temperature water storage tank enters the cold side of the pre-cooler to cool the working medium, and then returns to the high-temperature water storage tank for storage;

[0021] The high-temperature molten salt in the high-temperature molten salt tank enters the molten salt side of the molten salt heat exchanger to release heat, and then returns to the low-temperature molten salt tank for storage.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The system of the present invention is a solar thermal power generation system with energy storage designed specifically for "photovoltaic +". The CO2 cycle solar thermal power generation system can use the cold energy stored in the heat pump system to cool the low-temperature end to a lower temperature, improving the overall efficiency of the power generation system. Due to the setting of the recuperator in the present invention, the inlet temperature of the compressor is increased, and with the direct heating of an appropriate electric heater, the heat storage temperature of the heat pump system can be increased to the heat storage temperature of the CO2 cycle solar thermal power generation system. Direct molten salt heat storage is adopted, removing the heat transfer oil system, and the power generation cycle supporting the heat pump cycle and the CO2 cycle solar thermal power generation system are the same cycle, without adding any new equipment, saving investment, and overcoming the problems of the traditional electro-thermal energy storage system with a relatively low heat storage temperature (not exceeding 400 °C), requiring heat transfer oil heat storage, and requiring independent heat pump cycles and power generation cycles, and the power generation system cannot be combined with the CO2 cycle solar thermal power generation system, increasing a large number of equipment and large investment. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic structural diagram of the system of the present invention;

[0025] Figure 2 is a schematic diagram of the operating part of the system during the power generation condition of the present invention;

[0026] Figure 3 is a schematic diagram of the operating part of the system during the energy storage condition of the present invention.

[0027] In the diagram, 1 is the solar collector, 2 is the high-temperature molten salt tank, 3 is the molten salt heat exchanger, 4 is the low-temperature molten salt tank, 5 is the CO2 turbine, 6 is the high-temperature regenerator, 7 is the low-temperature regenerator, 8 is the precooler, 9 is the main compressor, 10 is the recompressor, 11 is the low-temperature water storage tank, 12 is the high-temperature water storage tank, 13 is the low-temperature expander, 14 is the high-temperature compressor, and 15 is the electric heater. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to the accompanying drawings.

[0029] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0030] like Figure 1 As shown, a CO2 cycle solar thermal power generation system for "photovoltaic+" includes a thermal storage system, a CO2 power generation system, a CO2 heat pump system, and a cold storage system.

[0031] The heat storage system includes a collector 1, a high-temperature molten salt tank 2, a molten salt heat exchanger 3, and a low-temperature molten salt tank 4. The outlet of the collector 1 is connected to the inlet of the high-temperature molten salt tank 2. The outlet of the high-temperature molten salt tank 2 is connected to the high-temperature inlet of the molten salt heat exchanger 3. The low-temperature outlet of the molten salt heat exchanger 3 is connected to the inlet of the low-temperature molten salt tank 4. The outlet of the low-temperature molten salt tank 4 is connected to the inlet of the collector 1.

[0032] The CO2 power generation system includes a CO2 turbine 5, a high-temperature regenerator 6, a low-temperature regenerator 7, a precooler 8, a main compressor 9, and a recompressor 10. The high-temperature outlet on the CO2 side of the molten salt heat exchanger 3 is connected to the inlet of the CO2 turbine 5. The outlet of the CO2 turbine 5 is connected to the low-pressure high-temperature inlet of the high-temperature regenerator 6. The low-pressure low-temperature outlet of the high-temperature regenerator 6 is connected to the low-pressure high-temperature inlet of the low-temperature regenerator 7. The low-pressure low-temperature outlet of the low-temperature regenerator 7 is divided into two paths, one of which connects to the recompressor. The inlet of 10 is connected, and the other path is connected to the CO2 side high temperature side inlet of the precooler 8. The CO2 side low temperature side outlet of the precooler 8 is connected to the inlet of the main compressor 9. The outlet of the main compressor 9 is connected to the high pressure low temperature side inlet of the low temperature regenerator 7. The high pressure high temperature side outlet of the low temperature regenerator 7 merges with the outlet of the re-compressor 10 and is connected to the high pressure low temperature side inlet of the high temperature regenerator 6. The high pressure high temperature side outlet of the high temperature regenerator 6 is connected to the CO2 side low temperature side inlet of the molten salt heat exchanger 3.

[0033] The heat pump system includes an electric heater 15, a low-temperature expander 13, and a high-temperature compressor 14. The CO2 side outlet of the electric heater 15 is connected to the CO2 side high-temperature side inlet of the molten salt heat exchanger 3. The CO2 side low-temperature side outlet of the molten salt heat exchanger 3 is connected to the high-pressure high-temperature side inlet of the high-temperature regenerator 6. The high-pressure low-temperature side outlet of the high-temperature regenerator 6 is connected to the high-pressure high-temperature side inlet of the low-temperature regenerator 7. The high-pressure low-temperature end of the low-temperature regenerator 7 is connected to the inlet of the low-temperature expander 13. The outlet of the low-temperature expander 13 is connected to the CO2 side low-temperature end of the precooler 8. The CO2 side high-temperature inlet of the precooler 8 is connected to the low-pressure low-temperature side inlet of the low-temperature regenerator 7. The low-pressure high-temperature side outlet of the low-temperature regenerator 7 is connected to the low-pressure low-temperature side inlet of the high-temperature regenerator 6. The low-pressure high-temperature side outlet of the high-temperature regenerator 6 is connected to the inlet of the high-temperature compressor 14. The outlet of the high-temperature compressor 14 is connected to the CO2 side inlet of the electric heater 15.

[0034] The cold storage system includes a low-temperature water storage tank 11 and a high-temperature water storage tank 12. The low-temperature water storage tank 11 is connected to the low-temperature water inlet of the precooler 8, and the high-temperature water storage tank 12 is connected to the high-temperature water inlet of the precooler 8.

[0035] The high-temperature regenerator 6, low-temperature regenerator 7, precooler 8, and molten salt heat exchanger 3 are shared by the CO2 cycle and the heat pump cycle. The design parameters of these devices are designed according to the highest parameters of the cycle used. Specifically, the high-temperature regenerator 6 is designed at 25MPa and 420℃, the low-temperature regenerator 7 is designed at 25MPa and 270℃, the precooler 8 is designed at 8MPa and 100℃, the molten salt heat exchanger 3 is designed at 600℃, the low-temperature water storage is designed at 10℃, and the high-temperature water storage is designed at 20℃.

[0036] A CO2-cycle solar thermal power generation method based on the aforementioned "photovoltaic+" system is proposed. This system has the function of regulating grid load changes. During peak photovoltaic power generation (approximately 9 AM to 5 PM), it functions as an energy storage system, absorbing the surplus photovoltaic power, with the specific timing determined according to geographical location and season. During peak electricity consumption periods (morning and evening peaks), the solar thermal system maintains full output based on local grid data; it ceases operation during off-peak periods. Therefore, the CO2-cycle solar thermal power generation method operates in two modes: energy storage mode and power generation mode.

[0037] 1. Energy storage operating conditions, such as Figure 3As shown, when the photovoltaic system is at its peak power generation period, this system enters energy storage mode, with the thermal storage system and heat pump system operating simultaneously. The shared equipment is used by these two systems, while the CO2 power generation system stops operating or operates at minimum load. At this time, some of the photovoltaic system's electricity should be in a state of being wasted and unable to be connected to the grid. This system uses this part of the electricity to drive the high-temperature compressor 14 to compress the low-pressure CO2 to high-pressure and high-temperature. The high-pressure and high-temperature CO2 enters the CO2 side of the electric heater 15 for further heating, and then enters the CO2 side of the molten salt heat exchanger 3 to release heat. After that, it enters the high-temperature regenerator 6 and the low-temperature regenerator 7 in sequence to continue releasing heat, and then enters the low-temperature expander 13 to expand and do work, recovering some energy. The expanded CO2 working fluid is at a low temperature and enters the CO2 side of the precooler 8 to output cold energy. After the precooler 8 absorbs heat, it enters the low-temperature regenerator 7 and the high-temperature regenerator 6 in sequence to continue absorbing heat. The preheated CO2 enters the high-temperature compressor 14 for compression, completing the CO2 heat pump cycle.

[0038] At the same time, the hot water in the high-temperature water storage tank 12 is transported to the water side of the precooler 8 to release heat, and the cold water that absorbs the cold energy returns to the low-temperature water storage tank 11 for storage.

[0039] Meanwhile, the molten salt in the low-temperature molten salt tank 4 is divided into two paths. One path enters the solar collector 1 to absorb the heat of solar energy. After being heated, it enters the high-temperature molten salt tank 2 for storage. The other path enters the molten salt side of the molten salt heat exchanger 3 to absorb the heat of high-temperature CO2. After being heated, it enters the high-temperature molten salt tank 2 for storage.

[0040] 2. Power generation conditions, such as Figure 2 As shown, when the local power grid is in peak electricity consumption period, the CO2 circulating solar thermal power generation system is started. First, CO2 enters the molten salt heat exchanger 3 and is heated to a high temperature. Then it enters the CO2 turbine 5 to do work. After that, it enters the low-pressure side of the high-temperature regenerator 6 and the low-temperature regenerator 7 to release heat. Then, part of the CO2 enters the re-compressor 10 and is directly pressurized, while another part of the CO2 enters the precooler 8 to be further cooled. Then it enters the main compressor 9 and is pressurized. Then it enters the high-pressure side of the low-temperature regenerator 7 to absorb heat. After that, it merges with the CO2 at the outlet of the re-compressor 10 and enters the high-pressure side of the high-temperature regenerator 6 to absorb heat. Finally, it returns to the CO2 inlet of the molten salt heat exchanger 3.

[0041] Meanwhile, the low-temperature water in the low-temperature water storage tank 11 enters the cold side of the precooler 8 as a cooling medium, and then returns to the high-temperature water storage tank 12 for storage.

[0042] Meanwhile, the high-temperature molten salt stored in the high-temperature molten salt tank 2 enters the molten salt side of the molten salt heat exchanger 3 to release heat, and then returns to the low-temperature molten salt tank 4 for storage.

[0043] In this invention, several main devices such as the high-temperature recuperator, low-temperature recuperator, pre-cooler, molten salt heat exchanger, etc. are shared by the CO2 cycle and the heat pump cycle. The design parameters of these devices are designed according to the highest parameters in the used cycle. Due to the design of shared devices, the equipment investment cost is greatly reduced and the system economy is increased. At the same time, due to the use of the recuperator design, the inlet temperature of the high-temperature compressor is increased. By cooperating with a proper electric heater for direct heating, the heat storage temperature of the heat pump system can be increased to the heat storage temperature of the CO2 cycle solar thermal power generation system. Molten salt heat storage is directly adopted, the heat transfer oil system is removed, and the power generation cycle supporting the heat pump cycle is the same cycle as the CO2 cycle solar thermal power generation system, without adding any new equipment. Further investment is saved. In addition, the CO2 cycle solar thermal power generation system can use the cold energy stored in the heat pump system to cool the low-temperature end to a lower temperature, thereby further improving the overall efficiency of the power generation system.

[0044] The specific embodiments described above have further elaborated on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only the specific embodiments of the present invention and is not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A carbon dioxide cycle solar thermal power generation system, characterized in that, This includes thermal storage systems, CO2 power generation systems, CO2 heat pump systems, and cold storage systems; The heat pump system includes an electric heater (15), a low-temperature expander (13) and a high-temperature compressor (14). The CO2 side outlet of the electric heater (15) and the low-temperature expander (13) are connected to the CO2 power generation system, and the high-temperature compressor (14) is connected to the electric heater (15). The CO2 power generation system includes a CO2 turbine (5), a high-temperature regenerator (6), a low-temperature regenerator (7), a precooler (8), a main compressor (9), and a re-compressor (10). The high-temperature outlet of the molten salt heat exchanger (3) on the CO2 side is connected to the inlet of the CO2 turbine (5). The outlet of the CO2 turbine (5) is connected to the low-pressure high-temperature inlet of the high-temperature regenerator (6). The low-pressure low-temperature outlet of the high-temperature regenerator (6) is connected to the low-pressure high-temperature inlet of the low-temperature regenerator (7). The outlets of the low-pressure low-temperature side of the low-temperature regenerator (7) are connected to each other. One outlet is connected to the inlet of the recompressor (10), and the other outlet is connected to the CO2 side high-temperature side inlet of the precooler (8). The CO2 side low-temperature side outlet of the precooler (8) merges with the outlet of the recompressor (10) and then connects to the high-pressure low-temperature side inlet of the high-temperature regenerator (6). The high-pressure high-temperature side outlet of the high-temperature regenerator (6) is connected to the thermal storage system. The precooler (8) is also connected to the cold storage system. The CO2 side outlet of the electric heater (15) is connected to the CO2 side high temperature side inlet of the molten salt heat exchanger (3). The CO2 side low temperature side outlet of the molten salt heat exchanger (3) is connected to the high pressure high temperature side inlet of the high temperature regenerator (6). The high pressure low temperature side outlet of the high temperature regenerator (6) is connected to the high pressure high temperature side inlet of the low temperature regenerator (7). The high pressure low temperature outlet of the low temperature regenerator (7) is connected to the inlet of the low temperature expander (13). The outlet of the low temperature expander (13) is connected to the CO2 side low temperature inlet of the precooler (8). The CO2 side high temperature outlet of the precooler (8) is connected to the low pressure low temperature side inlet of the low temperature regenerator (7). The low pressure high temperature side outlet of the low temperature regenerator (7) is connected to the low pressure low temperature side inlet of the high temperature regenerator (6). The low pressure high temperature side outlet of the high temperature regenerator (6) is connected to the inlet of the high temperature compressor (14). The outlet of the high temperature compressor (14) is connected to the CO2 side inlet of the electric heater (15).

2. The carbon dioxide cycle solar thermal power generation system according to claim 1, characterized in that, The heat storage system includes a collector (1), a high-temperature molten salt tank (2), a molten salt heat exchanger (3), and a low-temperature molten salt tank (4). The outlet of the collector (1) is connected to the inlet of the high-temperature molten salt tank (2). The outlet of the high-temperature molten salt tank (2) is connected to the high-temperature inlet of the molten salt heat exchanger (3). The low-temperature outlet of the molten salt heat exchanger (3) is connected to the inlet of the low-temperature molten salt tank (4). The outlet of the low-temperature molten salt tank (4) is connected to the inlet of the collector (1). The high-pressure high-temperature outlet of the high-temperature regenerator (6) is connected to the low-temperature inlet of the CO2 side of the molten salt heat exchanger (3).

3. A carbon dioxide cycle solar thermal power generation system according to claim 2, characterized in that, The CO2 side outlet of the electric heater (15) is connected to the CO2 side high temperature side inlet of the molten salt heat exchanger (3), and the CO2 side low temperature side outlet of the molten salt heat exchanger (3) is connected to the high pressure high temperature side inlet of the high temperature regenerator (6).

4. A carbon dioxide cycle solar thermal power generation system according to claim 1, characterized in that, The CO2-side low-temperature outlet of the precooler (8) is connected to the inlet of the main compressor (9), the outlet of the main compressor (9) is connected to the high-pressure low-temperature inlet of the low-temperature regenerator (7), and the high-pressure high-temperature outlet of the low-temperature regenerator (7) is connected to the high-pressure low-temperature inlet of the high-temperature regenerator (6) after merging with the outlet of the re-compressor (10).

5. A carbon dioxide cycle solar thermal power generation system according to claim 1, characterized in that, The cold storage system includes a low-temperature water storage tank (11) and a high-temperature water storage tank (12). The low-temperature water storage tank (11) is connected to the water-side low-temperature inlet of the precooler (8), and the high-temperature water storage tank (12) is connected to the water-side high-temperature inlet of the precooler (8).

6. A method for operating a carbon dioxide cycle solar thermal power generation system according to claim 5, characterized in that, Includes the following steps: When the photovoltaic system is in its peak period during the day, it enters the energy storage mode, compressing the low-pressure CO2 to high-pressure and high-temperature. The high-pressure and high-temperature CO2 enters the CO2 side of the electric heater (15) to continue to be heated, and then enters the CO2 side of the molten salt heat exchanger (3) to release heat. After that, it enters the high-pressure side of the high-temperature regenerator (6) and the low-temperature regenerator (7) to continue to release heat, and then enters the low-temperature expander (13) to expand and do work. The expanded CO2 working fluid is at a low temperature and enters the CO2 side of the precooler (8) to output cold energy. After the precooler (8) absorbs heat, it enters the low-pressure side of the low-temperature regenerator (7) and the high-temperature regenerator (6) to continue to absorb heat. The preheated CO2 enters the high-temperature compressor (14) to be compressed, completing the CO2 heat pump cycle.

7. A method for operating a carbon dioxide cycle solar thermal power generation system according to claim 6, characterized in that, The hot water in the high-temperature water storage tank (12) is transported to the water side of the precooler (8) to release heat and the cold water after absorbing the cold energy is returned to the low-temperature water storage tank (11) for storage. The molten salt in the low-temperature molten salt tank (4) is divided into two paths. One path enters the solar collector (1) to absorb the heat of solar energy. After being heated, it enters the high-temperature molten salt tank (2) for storage. The other path enters the molten salt side of the molten salt heat exchanger (3) to absorb the heat of high-temperature CO2. After being heated, it enters the high-temperature molten salt tank (2) for storage.

8. A method for operating a carbon dioxide cycle solar thermal power generation system according to claim 6, characterized in that, When the local power grid is in peak electricity demand, CO2 enters the molten salt heat exchanger (3) and is heated to a high temperature. Then it enters the CO2 turbine (5) to do work. After that, it enters the low-pressure side of the high-temperature regenerator (6) and the low-temperature regenerator (7) to release heat. Then, part of the CO2 enters the re-compressor (10) and is directly pressurized. Another part of the CO2 enters the precooler (8) and is further cooled. Then it enters the main compressor (9) to be pressurized. Then it enters the high-pressure side of the low-temperature regenerator (7) to absorb heat. After that, it merges with the CO2 at the outlet of the re-compressor (10) and enters the high-pressure side of the high-temperature regenerator (6) to absorb heat. Finally, it returns to the CO2 inlet of the molten salt heat exchanger (3).

9. A method for operating a carbon dioxide cycle solar thermal power generation system according to claim 8, characterized in that, The low-temperature water in the low-temperature water storage tank (11) enters the cold side of the precooler (8) as a cooling medium, and then returns to the high-temperature water storage tank (12) for storage; The high-temperature molten salt in the high-temperature molten salt tank (2) releases heat on the molten salt side of the molten salt heat exchanger (3) and then returns to the low-temperature molten salt tank (4) for storage.

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