Flexible energy storage and heat grade improvement system and method for dual-voltage Carnot cell

Abstract

The invention discloses a dual-pressure Carnot battery flexible energy storage and heat grade improvement system and method, and the system comprises a dual-pressure heat pump circulation unit, a high-temperature heat storage circulation unit, a medium-temperature heat storage circulation unit and a dual-pressure power generation circulation unit. According to the system, gradient improvement of the heat energy grade can be achieved, and an efficient energy storage system capable of supplying multi-grade heat energy is built. The system is provided with three functional modes including a rated mode, a high-grade heat supply mode and a high-power generation mode, and the three functional modes can be flexibly switched according to requirements so as to adapt to different energy demand scenes. According to the method, the peak load of the power grid can be effectively relieved, the flexibility and the stability of heat energy supply are guaranteed, remarkable advantages are shown in the aspects of improving the energy utilization efficiency and reducing the energy cost, and a new technical means is provided for constructing a more efficient and flexible energy storage system.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage, and particularly to a dual-pressure Carnot battery flexible energy storage and heat grade improvement system and method. Background Art

[0002] Energy storage technology, as a key link in realizing efficient energy utilization and optimizing the energy structure, has received extensive attention. However, there is a spatio-temporal mismatch between the intermittency of renewable energy output (such as the day-night fluctuation of photovoltaic power generation) and the dynamics of energy demand (such as the peak-valley difference of seasonal heating / cooling loads), resulting in a sharp increase in the demand for grid regulation capacity. Although traditional heat pump systems can achieve short-term heat storage through heat energy transfer, their narrow temperature range operation characteristics (usually <80°C) are difficult to meet the high-grade heat energy demands such as industrial process heating. In addition, traditional heat pump systems also have problems of energy efficiency decay under variable operating conditions and instability of the thermodynamic cycle, restricting the flexibility of multi-energy complementary systems.

[0003] As a new type of energy storage technology, the Carnot battery is based on the principle of thermodynamic cycle and realizes energy storage and release through the conversion of heat energy and electrical energy. With its high thermoelectric conversion efficiency as the core advantage and the ability of self-adaptive adjustment under operating conditions, it can effectively respond to the fluctuations of grid frequency and the changes in load demands. Compared with technologies such as pumped storage and compressed air energy storage, the Carnot battery does not need to rely on specific geological conditions, has geographical environmental universality, and can support the flexible deployment of distributed energy storage systems. These characteristics make it show important application potential in suppressing the fluctuations of renewable energy output and improving the flexibility of the power system.

[0004] Chinese patent document with the publication number CN119686830A discloses a Carnot battery system for cascaded heating of heat network water and its operation method, including a steam turbine power generation system, a heat network water heating system, an electric-to-heat conversion system, and a storage tank heat storage and release system. Based on the Carnot battery system, a heat network heat exchanger is added to the heat storage part of the storage tank system, and the temperature of the heat storage medium entering the heat source heat exchanger is reduced by heating the heat network water, so as to expand the thermoelectric load characteristic range of the system and improve the COP and round-trip efficiency of the system. The heat network water also reduces the heat exchange loss due to the cascaded heating system, improving the energy utilization rate.

[0005] Chinese patent document with the publication number CN118971052A discloses a Carnot battery system coupled with a transcritical Rankine cycle and a carbon dioxide heat pump, which includes a transcritical carbon dioxide cycle loop, a molten salt cycle loop, and a transcritical water vapor Rankine cycle loop. During the charging mode, the transcritical water vapor Rankine cycle loop does not work, and the system realizes the consumption of excess power and converts it into heat energy for storage; during the power generation mode, the transcritical carbon dioxide cycle loop does not work, and the heat energy stored in the system is converted into electrical energy again.

[0006] However, the existing energy utilization mode of the Carnot battery energy storage technology is relatively fixed, which restricts the operation flexibility of the system, making it difficult to adapt to complex energy supply scenarios. In particular, the regulation ability for heat supply is insufficient, the dependence on grid power purchase is high, the investment cost recovery period is long, and the return rate is low. Summary of the Invention

[0007] The present invention provides a dual-pressure Carnot battery flexible energy storage and heat grade improvement system and method. By coupling low-grade waste heat and adopting a dual-pressure boundary control strategy, the cascade improvement of the heat grade is realized, and an efficient energy storage system capable of supplying multi-grade heat energy is constructed, which can relieve the peak load of the power grid and ensure the flexibility and stability of heat supply.

[0008] A dual-pressure Carnot battery flexible energy storage and heat grade improvement system includes a dual-pressure heat pump cycle unit, a high-temperature heat storage cycle unit, a medium-temperature heat storage cycle unit, and a dual-pressure power generation cycle unit; The dual-pressure heat pump cycle unit includes an evaporator, a cold end of a regenerator, a first-stage compressor, a hot end of the regenerator, a compression and flow control valve group, a second-stage compressor, a hot end of a first heat exchanger, a hot end of a second heat exchanger, and a pressure reducing valve connected in series in a cycle; a pipeline is also provided at the outlet of the compression and flow control valve group and connected to the inlet of the hot end of the second heat exchanger; The high-temperature heat storage cycle unit includes a first high-temperature heat storage tank, a first working medium pump, a first heat supply end, a hot end of a third heat exchanger, a second high-temperature heat storage tank, and a cold end of a first heat exchanger connected in series in a cycle; The medium-temperature heat storage cycle unit includes a first medium-temperature heat storage tank, a hot end of a fourth heat exchanger, a second medium-temperature heat storage tank, a second working medium pump, and a cold end of a second heat exchanger connected in series in a cycle; a second heat supply end is also connected between the outlet of the first medium-temperature heat storage tank and the inlet of the second medium-temperature heat storage tank; The dual-pressure power generation cycle unit includes a first expander, an expansion and flow control valve group, a cold end of a third heat exchanger, a second expander, a condenser, a third working medium pump, and a cold end of a fourth heat exchanger connected in series in a cycle; a pipeline is also provided at the outlet of the expansion and flow control valve group and connected to the inlet of the condenser.

[0009] Preferably, the circulating working medium used in the dual-pressure heat pump cycle unit is an environmentally friendly hydrofluoroolefin, and the compression stage of the circulating working medium is adjusted by the compression and flow control valve group to achieve the compression stage; When the outlet of the compression and flow control valve group is directly connected to the inlet of the hot end of the second heat exchanger, the circulating working medium is compressed to a subcritical state by the first-stage compressor; When the outlet of the compression and flow control valve group is connected to the second-stage compressor, the circulating working medium is first compressed to a subcritical state by the first-stage compressor and then compressed to a supercritical state by the second-stage compressor.

[0010] The dual-pressure power generation cycle unit adjusts the expansion stage of the power generation working medium through the expansion and flow control valve group.

[0011] Preferably, the working temperature of the high-temperature heat storage cycle unit is 100~200°C, and the working temperature of the medium-temperature heat storage cycle unit is 50~100°C. The heat storage working medium of both the high-temperature heat storage cycle unit and the medium-temperature heat storage cycle unit is pressurized ethylene glycol aqueous solution.

[0012] Preferably, the evaporator uses low-grade waste heat sources for evaporation, including air, geothermal heat, and solar heat; the condenser uses tap water for cooling.

[0013] A method for flexible energy storage and heat grade improvement of a dual-pressure Carnot battery, based on the above-mentioned dual-pressure Carnot battery flexible energy storage and heat grade improvement system, includes: adjusting the shunt through a compression shunt regulating valve group and an expansion shunt regulating valve group, so that the dual-pressure Carnot battery flexible energy storage and heat grade improvement system realizes three functional modes, namely the rated mode, the high-grade heat supply mode, and the high-power power generation mode, and each mode corresponds to a charging state and a discharging state.

[0014] In the rated mode, the compression shunt regulating valve group adjusts the shunt, so that the outlet of the hot end of the regenerator is connected to the inlet of the hot end of the second heat exchanger after passing through the compression shunt regulating valve group; the expansion shunt regulating valve group adjusts the shunt, so that the outlet of the first expander is connected to the inlet of the condenser after passing through the expansion shunt regulating valve group; In the charging state of this mode, the dual-pressure heat pump cycle unit and the medium-temperature heat storage cycle unit are operated; at this time, the heat pump working medium at the outlet of the compression shunt regulating valve group flows to the hot end of the second heat exchanger, and the second working medium pump pressurizes the heat storage medium in the second medium-temperature heat storage tank and absorbs heat at the cold end of the second heat exchanger, and after heating, it is stored in the first medium-temperature heat storage tank; In the discharging state of this mode, the dual-pressure power generation cycle unit is operated; among them, the power generation working medium at the outlet of the expansion shunt regulating valve group flows to the condenser; a part of the first medium-temperature heat storage tank provides medium and low-grade heat energy through the second heat supply end, and another part is used for the dual-pressure power generation cycle unit to evaporate the power generation working medium through the hot end of the fourth heat exchanger, and the external output of work is realized in the first expander.

[0015] Furthermore, in the high-grade heat supply mode, the compression shunt regulating valve group adjusts the shunt, so that the outlet of the hot end of the regenerator is sequentially connected to the second-stage compressor, the hot end of the first heat exchanger, and the inlet of the hot end of the second heat exchanger after passing through the compression shunt regulating valve group; the expansion shunt regulating valve group adjusts the shunt, so that the outlet of the first expander is connected to the inlet of the condenser after passing through the expansion shunt regulating valve group; In the charging state, the dual-pressure heat pump cycle unit, the high-temperature heat storage cycle unit, and the medium-temperature heat storage cycle unit are operated; at this time, the heat pump working medium at the outlet of the compression and diversion control valve group flows sequentially to the second-stage compressor, the hot end of the first heat exchanger, and the hot end of the second heat exchanger; the heat storage medium stored in the second high-temperature heat storage tank absorbs high-grade heat through the cold end of the first heat exchanger, and after heating, it is stored in the first high-temperature heat storage tank; the heat storage medium stored in the second medium-temperature heat storage tank is pressurized by the second working medium pump and absorbs medium-grade heat at the hot end of the second heat exchanger, and after heating, it is stored in the first medium-temperature heat storage tank. In the discharging state, the high-temperature heat storage cycle unit and the dual-pressure power generation cycle unit are operated; among them, the power generation working medium at the outlet of the expansion and diversion control valve group flows to the condenser; a part of the first medium-temperature heat storage tank provides medium- and low-grade heat energy to the outside through the second heat supply end, and another part is used for the dual-pressure power generation cycle unit to evaporate the power generation working medium through the hot end of the fourth heat exchanger, and the external output of work is realized in the first expansion machine; the high-temperature heat storage medium in the first high-temperature heat storage tank provides high-grade heat energy to the outside at the first heat supply end through the first working medium pump, and after cooling, it returns to the second high-temperature heat storage tank through the hot end of the third heat exchanger. At this time, there is no flow in the cold end of the third heat exchanger, and no heat exchange occurs.

[0016] Furthermore, in the high-power power generation mode, the compression and diversion control valve group adjusts the shunt so that the outlet of the hot end of the regenerator is sequentially connected to the second-stage compressor, the hot end of the first heat exchanger, and the inlet of the hot end of the second heat exchanger after passing through the compression and diversion control valve group; the expansion and diversion control valve group adjusts the shunt so that the outlet of the first expansion machine is sequentially connected to the cold end of the third heat exchanger, the second expansion machine, and the inlet of the condenser after passing through the expansion and diversion control valve group. In the charging state, the dual-pressure heat pump cycle unit, the high-temperature heat storage cycle unit, and the medium-temperature heat storage cycle unit are operated; at this time, the heat pump working medium at the outlet of the compression and diversion control valve group flows sequentially to the second-stage compressor, the hot end of the first heat exchanger, and the hot end of the second heat exchanger; the heat storage medium stored in the second high-temperature heat storage tank absorbs high-grade heat through the cold end of the first heat exchanger, and after heating, it is stored in the first high-temperature heat storage tank; the heat storage medium stored in the second medium-temperature heat storage tank is pressurized by the second working medium pump and absorbs medium-grade heat at the hot end of the second heat exchanger, and after heating, it is stored in the first medium-temperature heat storage tank. In the discharging state, the high-temperature heat storage cycle unit and the dual-pressure power generation cycle unit are operated; among them, the power generation working medium at the outlet of the expansion and diversion control valve group flows sequentially to the cold end of the third heat exchanger, the second expansion machine, and the condenser; a part of the first medium-temperature heat storage tank provides medium- and low-grade heat energy to the outside through the second heat supply end, and another part is used for the dual-pressure power generation cycle unit to evaporate the power generation working medium through the hot end of the fourth heat exchanger, and the external output of work is realized in the first expansion machine; the power generation working medium after expanding in the first expansion machine absorbs the heat transmitted from the first high-temperature heat storage tank at the cold end of the third heat exchanger, and the heated power generation working medium expands again in the second expansion machine to output work externally, realizing high-power output.

[0017] Compared with the prior art, the present invention has the following beneficial effects: By coupling low-grade waste heat and adopting a dual-pressure boundary control strategy, the present invention realizes the cascaded improvement of the heat energy grade. This system can not only supply multi-grade heat energy, but also has three functional modes, which can be flexibly switched according to needs, including the rated mode, the high-grade heat supply mode, and the high-power power generation mode. These characteristics enable the system to show significant advantages in improving energy utilization efficiency, reducing energy costs, and responding to different energy demand scenarios, providing a new technical means for constructing a more efficient and flexible energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the overall structure of a dual-pressure Carnot battery flexible energy storage and heat grade improvement system of the present invention.

[0019] Figure 2 It is a schematic diagram of the operation of the rated mode in the present invention.

[0020] Figure 3 It is a schematic diagram of the charging state in the rated mode of the present invention.

[0021] Figure 4 It is a schematic diagram of the discharging state in the rated mode of the present invention.

[0022] Figure 5 It is a working diagram of the high-grade heat supply mode in the present invention.

[0023] Figure 6 It is a schematic diagram of the charging state in the high-grade heat supply mode of the present invention.

[0024] Figure 7 It is a schematic diagram of the discharging state in the high-grade heat supply mode of the present invention.

[0025] Figure 8 It is a working diagram of the high-power power generation mode in the present invention.

[0026] Figure 9 It is a schematic diagram of the charging state in the high-power power generation mode of the present invention.

[0027] Figure 10 It is a schematic diagram of the discharging state in the high-power power generation mode of the present invention.

[0028] In the figure: 1. Evaporator; 2. Regenerator; 3. First-stage compressor; 4. Compression and flow-dividing regulating valve group; 5. Second-stage compressor; 6. First heat exchanger; 7. Second heat exchanger; 8. Pressure-reducing valve; 9. First high-temperature heat storage tank; 10. First working fluid pump; 11. First heat supply end; 12. Third heat exchanger; 13. Second high-temperature heat storage tank; 14. First medium-temperature heat storage tank; 15. Second heat supply end; 16. Fourth heat exchanger; 17. Second medium-temperature heat storage tank; 18. Second working fluid pump; 19. First expander; 20. Expansion and flow-dividing regulating valve group; 21. Second expander; 22. Condenser; 23. Third working fluid pump. Detailed implementation manners

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be noted that the following embodiments are intended to facilitate the understanding of the present invention and do not limit it in any way.

[0030] As Figure 1 shown, a dual-pressure Carnot battery flexible energy storage and heat grade improvement system includes: a dual-pressure heat pump cycle unit, a high-temperature heat storage cycle unit, a medium-temperature heat storage cycle unit, and a dual-pressure power generation cycle unit.

[0031] The dual-pressure heat pump cycle unit is composed of an evaporator 1, a regenerator 2, a first-stage compressor 3, a compression and flow-dividing regulating valve group 4, a second-stage compressor 5, a first heat exchanger 6, a second heat exchanger 7, and a pressure-reducing valve 8 connected in sequence. The outlet of the evaporator 1 is connected to the cold-end inlet of the regenerator 2, the cold-end outlet of the regenerator 2 is connected to the inlet of the first-stage compressor 3, the outlet of the first-stage compressor 3 is connected to the hot-end inlet of the regenerator 2, and the hot-end outlet of the regenerator 2 is connected to the inlet of the compression and flow-dividing regulating valve group 4; the outlet of the compression and flow-dividing regulating valve group 4 is divided into two flow channels. One path is connected to the second-stage compressor 5 and the first heat exchanger 6 in sequence and then connected to the hot-end inlet of the second heat exchanger 7. Among them, the outlet of the second-stage compressor 5 is connected to the hot-end inlet of the first heat exchanger 6, and the hot-end outlet of the first heat exchanger 6 is connected to the hot-end inlet of the second heat exchanger 7; the other path is directly connected to the hot-end inlet of the second heat exchanger 7; the hot-end outlet of the second heat exchanger 7 is connected to the inlet of the pressure-reducing valve 8, and the outlet of the pressure-reducing valve 8 is connected to the inlet of the evaporator 1.

[0032] In the dual-pressure heat pump cycle unit, the direct connection between the regenerator 2 and the second heat exchanger can be achieved by adjusting the compression and diversion control valve group 4. In the dual-pressure heat pump cycle unit, after the heat pump working medium absorbs low-grade waste heat in the evaporator 1 and evaporates from the liquid state to the gaseous state, it exchanges heat with the high-temperature gas pressurized by the first compressor 3 in the first heat exchanger 2. By preheating, the temperature of the working medium entering and leaving the first compressor 3 can be increased. The high-temperature gas after heat exchange is divided into branches according to the system function mode selection through the compression and diversion control valve group 4. When the system is set to the high-grade heat supply mode or the high-power power generation mode, the working medium is further pressurized by the secondary compressor 5, and the high-temperature and high-pressure gas transfers high-grade heat to the high-temperature heat storage cycle unit through the first heat exchanger 6. The working medium after temperature reduction then transfers medium-grade heat to the medium-temperature heat storage cycle unit through the second heat exchanger 7. When the system is set to the rated mode, the working medium directly enters the second heat exchanger 7 to transfer medium-grade heat to the medium-temperature heat storage cycle unit. After condensation, all are depressurized by the pressure reducing valve 8 and absorb low-grade heat in the evaporator 1 to carry out a new round of cycle.

[0033] The high-temperature heat storage cycle unit is composed of a first high-temperature heat storage tank 9, a first working medium pump 10, a first heat supply end 11, a third heat exchanger 12, and a second high-temperature heat storage tank 13 connected in sequence. The outlet of the first high-temperature heat storage tank 9 is connected to the inlet of the first working medium pump 10, the outlet of the first working medium pump 10 is connected to the inlet of the first heat supply end 11, the outlet of the first heat supply end 11 is connected to the hot end inlet of the third heat exchanger 12, the hot end outlet of the third heat exchanger 12 is connected to the inlet of the second high-temperature heat storage tank 13, the outlet of the second high-temperature heat storage tank 13 is connected to the cold end inlet of the first heat exchanger 6, and the cold end outlet of the first heat exchanger 6 is connected to the inlet of the first high-temperature heat storage tank 9.

[0034] In the high-temperature heat storage cycle unit, the heat storage working medium that absorbs high-grade heat from the first heat exchanger 6 is stored in the first high-temperature heat storage tank 9, pressurized by the first working medium pump 10, and sent to the first heat supply end 11 for external supply of high-grade thermal energy. When the system is set to the rated mode or the high-grade heat supply mode, there is no working medium for heat exchange at the cold end of the third heat exchanger 12. The heat storage working medium after heat supply is stored in the second high-temperature heat storage tank 13 through the third heat exchanger 12 and absorbs high-grade heat in the first heat exchanger 6 to carry out a new round of cycle. When the system is set to the high-power power generation mode, the heat storage working medium after heat supply is heated again through the third heat exchanger 12 and stored in the second high-temperature heat storage tank 13, and absorbs high-grade heat in the first heat exchanger 6 to carry out a new round of cycle.

[0035] The medium-temperature heat storage and circulation unit consists of a first medium-temperature heat storage tank 14, a second heat supply end 15, a fourth heat exchanger 16, a second medium-temperature heat storage tank 17, and a second working fluid pump 18. The outlet of the first medium-temperature heat storage tank 14 is divided into two paths. One path is connected to the inlet of the second heat supply end 15, and the other path is connected to the hot-end inlet of the fourth heat exchanger 16. The outlet of the second heat supply end 15 and the hot-end outlet of the fourth heat exchanger 16 are simultaneously connected to the inlet of the second medium-temperature heat storage tank 17. The outlet of the second medium-temperature heat storage tank 17 is connected to the inlet of the second working fluid pump 18. The outlet of the second working fluid pump 18 is connected to the cold-end inlet of the second heat exchanger 7. The cold-end outlet of the second heat exchanger 7 is connected to the inlet of the first heat storage tank 14.

[0036] In the medium-temperature heat storage and circulation unit, the heat storage working fluid that absorbs medium-grade heat from the second heat exchanger 7 is stored in the first medium-temperature heat storage tank 14. The outlet of the first medium-temperature heat storage tank 14 is connected in parallel with the second heat supply end 15 for the external supply of medium-grade thermal energy and the fourth heat exchanger 16. The working fluid after heat exchange is stored in the second medium-temperature heat storage tank 17, and then after being pressurized by the second working fluid pump 18, it undergoes a new round of circulation.

[0037] The dual-pressure power generation circulation unit consists of a first expander 19, an expansion shunt regulating valve group 20, a second expander 21, a condenser 22, and a third working fluid pump 23. The outlet of the first expander 19 is connected to the inlet of the expansion shunt regulating valve group 20. The outlet of the expansion shunt regulating valve group 20 is divided into two flow paths. One path is sequentially connected to the cold end of the third heat exchanger 12, the second expander 21, and then connected to the inlet of the condenser 22. Among them, the cold-end outlet of the third heat exchanger 12 is connected to the inlet of the second expander 21, and the outlet of the second expander 21 is connected to the inlet of the condenser 22. The other path is directly connected to the inlet of the condenser 22. The outlet of the condenser 22 is connected to the inlet of the third working fluid pump 23. The outlet of the third working fluid pump 23 is connected to the cold-end inlet of the fourth heat exchanger 16. The cold-end outlet of the fourth heat exchanger 16 is connected to the inlet of the first expander 19.

[0038] In the dual-pressure power generation circulation unit, the power generation working fluid that absorbs heat and vaporizes in the fourth heat exchanger 16 enters the expander to expand and output work externally. When the system is set to the high-power power generation mode, the power generation working fluid enters the third heat exchanger 12 through the expansion shunt regulating valve group 20 to continue heating up, and enters the second expander 21 to expand again to output work externally, and then is condensed in the condenser 22. When the system is set to the high-grade heat supply mode or the rated mode, the power generation working fluid directly enters the condenser 22 to be condensed. The condensed power generation working fluid enters the third working fluid pump 23 to be pressurized, and absorbs medium-grade heat in the second heat exchanger 7 for a new round of circulation.

[0039] The specific operating principles of the three working modes are described as follows: (1) Rated mode, as Figure 2 shown.

[0040] During charging, the dual-pressure heat pump cycle unit and the medium-temperature heat storage cycle unit operate. At this time, the compression shunt regulating valve group 4 adjusts the shunt so that the heat pump working medium at its outlet flows to the second heat exchanger 7. The second working medium pump 18 pressurizes the heat storage medium in the second medium-temperature heat storage tank 17 and absorbs heat in the second heat exchanger 7, and after the temperature rises, it is stored in the first medium-temperature heat storage tank 14, as Figure 3 shown.

[0041] During discharging, the dual-pressure power generation cycle unit operates. Among them, the expansion shunt regulating valve group 20 adjusts the shunt so that the power generation working medium at its outlet flows to the condenser 22. A part of the first medium-temperature heat storage tank 14 can provide medium- and low-grade heat energy to the outside through the second heat supply end 15, and the other part is used for the dual-pressure power generation cycle unit through the fourth heat exchanger 16 to evaporate the power generation working medium, and the external output of work is realized in the first expander 19, as Figure 4 shown.

[0042] (2) High-grade heat supply mode, as Figure 5 shown.

[0043] During charging, the dual-pressure heat pump cycle unit, the high-temperature heat storage cycle unit and the medium-temperature heat storage cycle unit operate. At this time, the compression shunt regulating valve group 4 adjusts the shunt so that the heat pump working medium at its outlet flows to the secondary compressor 5, the first heat exchanger 6, and the second heat exchanger 7 in sequence. The heat storage medium stored in the second high-temperature heat storage tank 13 absorbs high-grade heat through the first heat exchanger 6, and after the temperature rises, it is stored in the first high-temperature heat storage tank 9; the heat storage medium stored in the second medium-temperature heat storage tank 17 is pressurized by the second working medium pump 18 and absorbs medium-grade heat at the hot end of the second heat exchanger 7, and after the temperature rises, it is stored in the first medium-temperature heat storage tank 14, as Figure 6 shown.

[0044] During discharging, the high-temperature heat storage cycle unit and the dual-pressure power generation cycle unit operate. The expansion shunt regulating valve group 20 adjusts the shunt so that the power generation working medium at its outlet flows to the condenser 22. The high-temperature heat storage medium in the first high-temperature heat storage tank 9 provides high-grade heat energy to the outside through the first working medium pump 10 at the first heat supply end 11, and after the temperature drops, it returns to the second high-temperature heat storage tank 13 through the third heat exchanger 12 (at this time, there is no flow in the cold end of the third heat exchanger, and no heat exchange occurs), as Figure 7 shown.

[0045] (3) High-power power generation mode, as Figure 8 shown.

[0046] During charging, the dual-pressure heat pump cycle unit, the high-temperature heat storage cycle unit, and the medium-temperature heat storage cycle unit are operated. At this time, the compression shunt regulating valve group 4 adjusts the shunt so that the heat pump working medium at its outlet flows sequentially to the secondary compressor 5, the first heat exchanger 6, and the second heat exchanger 7. The heat storage medium stored in the second high-temperature heat storage tank 13 absorbs high-grade heat through the first heat exchanger 6 and is stored in the first high-temperature heat storage tank 9 after temperature rise; the heat storage medium stored in the second medium-temperature heat storage tank 17 is pressurized by the second working medium pump 18 and absorbs medium-grade heat at the hot end of the second heat exchanger 7, and is stored in the first medium-temperature heat storage tank 14 after temperature rise, as Figure 9 shown.

[0047] During discharging, the high-temperature heat storage cycle unit and the dual-pressure power generation cycle unit are operated. The expansion shunt regulating valve group 20 adjusts the shunt so that the power generation working medium at its outlet flows sequentially to the third heat exchanger 12, the second expander 21, and the condenser 22. The power generation working medium expanded by the first expander 19 absorbs the heat conveyed by the first high-temperature heat storage tank 9 at the cold end of the third heat exchanger 12, and the heated power generation working medium expands again in the second expander 21 to output work externally, realizing high-power output, as Figure 10 shown.

[0048] The above-described embodiments have described in detail the technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modification, supplement, and equivalent replacement made within the principle scope of the present invention shall be included within the protection scope of the present invention.

Claims

1. A dual-pressure Carnot battery flexible energy storage and thermal grade improvement system, characterized in that, It includes a dual-pressure heat pump cycle unit, a high-temperature heat storage cycle unit, a medium-temperature heat storage cycle unit, and a dual-pressure power generation cycle unit; The dual-pressure heat pump cycle unit includes an evaporator (1), the cold end of a recuperator (2), a first-stage compressor (3), the hot end of the recuperator (2), a compression and flow control valve group (4), a second-stage compressor (5), the hot end of a first heat exchanger (6), the hot end of a second heat exchanger (7), and a pressure reducing valve (8) connected in series in a cycle; A pipeline is also provided at the outlet of the compression and flow control valve group (4) and connected to the inlet of the hot end of the second heat exchanger (7); The high-temperature heat storage cycle unit includes a first high-temperature heat storage tank (9), a first working fluid pump (10), a first heat supply end (11), the hot end of a third heat exchanger (12), a second high-temperature heat storage tank (13), and the cold end of the first heat exchanger (6) connected in series in a cycle; The medium-temperature heat storage cycle unit includes a first medium-temperature heat storage tank (14), the hot end of a fourth heat exchanger (16), a second medium-temperature heat storage tank (17), a second working fluid pump (18), and the cold end of the second heat exchanger (7) connected in series in a cycle; A second heat supply end (15) is also connected between the outlet of the first medium-temperature heat storage tank (14) and the inlet of the second medium-temperature heat storage tank (17); The dual-pressure power generation cycle unit includes a first expander (19), an expansion and flow control valve group (20), the cold end of a third heat exchanger (12), a second expander (21), a condenser (22), a third working fluid pump (23), and the cold end of a fourth heat exchanger (16) connected in series in a cycle; A pipeline is also provided at the outlet of the expansion and flow control valve group (20) and connected to the inlet of the condenser (22).

2. The dual-pressure Carnot battery flexible energy storage and thermal grade improvement system according to claim 1, wherein The circulating working fluid used in the dual-pressure heat pump cycle unit is hydrofluoroolefin, and the compression stage of the circulating working fluid is adjusted by the compression and flow control valve group (4); When the outlet of the compression and flow control valve group (4) is directly connected to the inlet of the hot end of the second heat exchanger (7), the circulating working fluid is compressed to a subcritical state by the first-stage compressor (3); When the outlet of the compression and flow control valve group (4) is connected to the second-stage compressor (5), the circulating working fluid is first compressed to a subcritical state by the first-stage compressor (3) and then compressed to a supercritical state by the second-stage compressor (5).

3. The dual-pressure Carnot battery flexible energy storage and thermal grade improvement system according to claim 1, wherein, The dual-pressure power generation cycle unit adjusts the flow path through the expansion and flow control valve group (20) to realize the expansion stage of the power generation working fluid.

4. The dual-pressure Carnot battery flexible energy storage and thermal grade improvement system according to claim 1, wherein The operating temperature of the high-temperature heat storage cycle unit is 100~200°C, and the operating temperature of the medium-temperature heat storage cycle unit is 50~100°C. The heat storage working fluids of the high-temperature heat storage cycle unit and the medium-temperature heat storage cycle unit are both pressurized ethylene glycol aqueous solutions.

5. The dual-pressure Carnot battery flexible energy storage and heat grade improvement system according to claim 1, characterized in that, The evaporator (1) uses low-grade waste heat sources for evaporation, including air, geothermal heat, and solar heat; The condenser (22) uses tap water for cooling.

6. A method for flexible energy storage and thermal grade improvement of a dual-pressure Carnot battery, characterized in that, Based on the dual-pressure Carnot battery flexible energy storage and heat grade improvement system according to any one of claims 1 to 5, it includes: By adjusting the flow path through the compression and flow control valve group (4) and the expansion and flow control valve group (20), the dual-pressure Carnot battery flexible energy storage and heat grade improvement system realizes three function modes, namely the rated mode, the high-grade heat supply mode, and the high-power power generation mode. Each mode corresponds to a charging state and a discharging state.

7. The method for flexible energy storage and thermal grade improvement of a dual-pressure Carnot battery according to claim 6, characterized in that, In the rated mode, the compression and diversion regulating valve group (4) regulates the diversion so that the hot-end outlet of the regenerator (2) is connected to the hot-end inlet of the second heat exchanger (7) after passing through the compression and diversion regulating valve group (4); the expansion and diversion regulating valve group (20) regulates the diversion so that the outlet of the first expander (19) is connected to the inlet of the condenser (22) after passing through the expansion and diversion regulating valve group (20). In the charging state of this mode, the dual-pressure heat pump cycle unit and the medium-temperature heat storage cycle unit are operated; at this time, the heat pump working medium at the outlet of the compression and diversion regulating valve group (4) flows to the hot end of the second heat exchanger (7), and the second working medium pump (18) pressurizes the heat storage medium in the second medium-temperature heat storage tank (17) and absorbs heat at the cold end of the second heat exchanger (7), and after heating, it is stored in the first medium-temperature heat storage tank (14). In the discharging state of this mode, the dual-pressure power generation cycle unit is operated; among them, the power generation working medium at the outlet of the expansion and diversion regulating valve group (20) flows to the condenser (22); a part of the first medium-temperature heat storage tank (14) provides medium- and low-grade heat energy to the outside through the second heat supply end (15), and another part is used at the hot end of the fourth heat exchanger (16) for the dual-pressure power generation cycle unit to evaporate the power generation working medium, and the external output of work is realized in the first expander (19).

8. The method for flexible energy storage and heat grade improvement of a double-pressure Carnot battery according to claim 6, wherein In the high-grade heat supply mode, the compression and diversion regulating valve group (4) regulates the diversion so that the hot-end outlet of the regenerator (2) is sequentially connected to the second-stage compressor (5), the hot end of the first heat exchanger (6), and the hot-end inlet of the second heat exchanger (7) after passing through the compression and diversion regulating valve group (4); the expansion and diversion regulating valve group (20) regulates the diversion so that the outlet of the first expander (19) is connected to the inlet of the condenser (22) after passing through the expansion and diversion regulating valve group (20). In the charging state of this mode, the dual-pressure heat pump cycle unit, the high-temperature heat storage cycle unit, and the medium-temperature heat storage cycle unit are operated; at this time, the heat pump working medium at the outlet of the compression and diversion regulating valve group (4) sequentially flows to the second-stage compressor (5), the hot end of the first heat exchanger (6), and the hot end of the second heat exchanger (7); the heat storage medium stored in the second high-temperature heat storage tank (13) absorbs high-grade heat through the cold end of the first heat exchanger (6), and after heating, it is stored in the first high-temperature heat storage tank (9); the heat storage medium stored in the second medium-temperature heat storage tank (17) is pressurized by the second working medium pump (18) and absorbs medium-grade heat at the hot end of the second heat exchanger (7), and after heating, it is stored in the first medium-temperature heat storage tank (14). In the discharging state, the high-temperature heat storage cycle unit and the dual-pressure power generation cycle unit operate. Among them, the working medium for power generation at the outlet of the expansion and diversion regulating valve group (20) flows to the condenser (22); a part of the first medium-temperature heat storage tank (14) provides medium- and low-grade heat energy to the outside through the second heat supply end (15), and another part is used at the hot end of the fourth heat exchanger (16) for the dual-pressure power generation cycle unit to evaporate the working medium for power generation, and the external output of work is realized in the first expander (19); the high-temperature heat storage medium in the first high-temperature heat storage tank (9) provides high-grade heat energy to the outside at the first heat supply end (11) through the first working medium pump (10), and after cooling, it returns to the second high-temperature heat storage tank (13) through the hot end of the third heat exchanger (12). At this time, there is no fluid flow at the cold end of the third heat exchanger (12), and no heat exchange occurs.

9. The method for flexible energy storage and thermal grade improvement of a double-pressure Carnot battery according to claim 6, wherein In the high-power power generation mode, the compression and diversion regulating valve group (4) adjusts the diversion so that the outlet of the hot end of the regenerator (2) is sequentially connected to the secondary compressor (5), the hot end of the first heat exchanger (6), and the inlet of the hot end of the second heat exchanger (7) after passing through the compression and diversion regulating valve group 4; the expansion and diversion regulating valve group (20) adjusts the diversion so that the outlet of the first expander (19) is sequentially connected to the cold end of the third heat exchanger (12), the second expander (21), and the inlet of the condenser (22) after passing through the expansion and diversion regulating valve group (20); In the charging state, the dual-pressure heat pump cycle unit, the high-temperature heat storage cycle unit, and the medium-temperature heat storage cycle unit operate. At this time, the heat pump working medium at the outlet of the compression and diversion regulating valve group (4) sequentially flows to the secondary compressor (5), the hot end of the first heat exchanger (6), and the hot end of the second heat exchanger (7); the heat storage medium stored in the second high-temperature heat storage tank (13) absorbs high-grade heat at the cold end of the first heat exchanger (6), and after heating up, it is stored in the first high-temperature heat storage tank (9); the heat storage medium stored in the second medium-temperature heat storage tank (17) is pressurized by the second working medium pump (18) and absorbs medium-grade heat at the hot end of the second heat exchanger (7), and after heating up, it is stored in the first medium-temperature heat storage tank (14); In the discharging state, the high-temperature heat storage cycle unit and the dual-pressure power generation cycle unit operate. Among them, the working medium for power generation at the outlet of the expansion and diversion regulating valve group (20) sequentially flows to the cold end of the third heat exchanger (12), the second expander (21), and the condenser (22); a part of the first medium-temperature heat storage tank (14) provides medium- and low-grade heat energy to the outside through the second heat supply end (15), and another part is used at the hot end of the fourth heat exchanger (16) for the dual-pressure power generation cycle unit to evaporate the working medium for power generation, and the external output of work is realized in the first expander (19); the working medium for power generation after expansion by the first expander (19) absorbs the heat transported by the first high-temperature heat storage tank (9) at the cold end of the third heat exchanger (12), and the heated working medium for power generation expands again in the second expander (21) to output work externally, realizing high-power output.

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