An electrical energy storage coupling system and method based on a positive and reverse supercritical carbon dioxide cycle

Abstract

The present invention relates to an electrical energy storage and coupling system and method based on a positive and reverse supercritical carbon dioxide cycle, belonging to the technical field of physical energy storage power generation. The electrical energy storage and coupling system based on the positive and reverse supercritical carbon dioxide cycle includes a charging subsystem, a power generation subsystem, and a heat storage subsystem. The method includes a conventional mode, an energy storage mode, an energy release mode, and a peak shaving method. The present invention is coupled by a power generation subsystem, a heat storage subsystem, and a charging subsystem. Through the compression power consumption of the charging subsystem, the system output is reduced, and heat is produced and stored to complete the energy storage process. By removing the power generation subsystem during the recompression process and using the high-temperature heat storage to assist in heating the branch working fluid, the system output is increased to complete the energy release process. The storage and release process of energy relies on the internal process reorganization and deep coupling of the cycle, has a higher round-trip efficiency, does not require additional auxiliary heat sources or waste heat resources, and has universality for high-temperature heat sources such as coal-based, nuclear energy, and solar thermal energy.

Description

Technical Field

[0001] The present invention relates to the technical field of physical energy storage power generation, and particularly to an electrical energy storage and coupling system and method based on a positive and reverse supercritical carbon dioxide cycle. Background Art

[0002] The proportion of green and renewable energy power in the future power system will increase significantly. However, new energy power generation such as photovoltaic and wind power has characteristics of volatility, intermittency and unpredictability. High-proportion new energy power generation faces problems such as difficult grid connection, difficult consumption and difficult scheduling. The difficulty of the power system's regulation ability to adapt to the large-scale grid connection of new energy has become one of the bottlenecks restricting China's energy transformation.

[0003] The closed supercritical carbon dioxide power cycle has advantages such as high efficiency, economy and compactness. At the same time, the system is simple and has a fast response speed, and has broad application prospects in traditional coal-fired, nuclear power, solar thermal and other new energy high-temperature power generation fields. It is an internationally recognized disruptive and cutting-edge technology.

[0004] Energy storage can effectively improve the flexible peak shaving capacity and is a good choice to promote the development of a new power system. When an energy storage system operates in a coupled manner with a thermal power generation system, it can effectively eliminate the peak-valley difference and suppress load fluctuations, and to a certain extent, improve the operation flexibility on the power supply side. In the coupled system of thermoelectricity and energy storage, energy storage involves many methods such as compressed gas energy storage, physical heat storage and heat pump electricity storage. The compressed / liquefied gas energy storage system itself has a relatively complex cycle process, and it is difficult to deeply couple and match the thermal power cycle. In addition, there are pressure fluctuations and throttling losses during the storage and release processes, and usually pressure storage is required, which affects the system economy. The configuration of the power cycle and physical heat storage coupled system is relatively simple, and the heat storage mainly comes from two methods: direct electric heating and extraction heat storage; electric heating does not affect the steam-water cycle of the power plant, but there is a typical problem of "using high-quality energy in a low-quality way", which affects the cycle efficiency. The stored heat can be directly used for heat utilization, but the application scenarios or demands are limited and the unit output cannot be increased. Heat pump electricity storage, that is, the Carnot battery, is a new type of large-scale energy storage method. It is not restricted by geographical conditions and has no pressure storage container, and has broad development prospects. When the heat pump electricity storage operates independently in a cycle, the working temperature levels of the positive and reverse cycles are quite the same. Coupled with irreversible factors such as physical properties and heat transfer temperature differences, its round-trip efficiency is generally low.

[0005] In previous energy storage systems, the coupling and matching between the thermal power cycle and the energy storage cycle were usually ignored, and there were energy throttling losses or high-quality energy being used in a low-quality way during the storage and release processes. Summary of the Invention

[0006] To solve the above problems, the present invention provides an electrical energy storage and coupling system and method based on a positive and reverse supercritical carbon dioxide cycle. During low electricity consumption periods or new energy power generation bursts, the charging subsystem is used to consume part of the electric power, produce low-grade heat energy and store it in the heat storage subsystem; during periods of insufficient external power or peak electricity consumption, the recompression process of the supercritical carbon dioxide power cycle is cut off, and the heat storage medium is used to assist in preheating the working fluid of the branch, reducing the self-power consumption of the power generation subsystem and increasing the net output; during periods of flat electricity consumption, the power generation subsystem operates independently and efficiently outputs the rated power.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] An electrical energy storage and coupling system based on a positive and reverse supercritical carbon dioxide cycle, characterized in that the system includes a charging subsystem, a heat storage subsystem and a power generation subsystem, and has the function of relying on internal energy interaction, storage and release within the subsystem to adjust the power load output of the system, wherein:

[0009] The charging subsystem is used to consume the excess power of the power generation subsystem and convert it into low-grade heat energy, and includes a compressor, a cooler, an expander, and a heater. The outlet of the compressor is connected to the inlet of the working fluid side of the cooler, the outlet of the working fluid side of the cooler is connected to the inlet of the expander, the outlet of the expander is connected to the inlet of the working fluid side of the heater, and the outlet of the working fluid side of the heater is connected to the inlet of the compressor;

[0010] The heat storage subsystem is used to intermittently store the heat energy produced by the charging subsystem and provide additional heat energy to the power generation subsystem, and includes a high-temperature storage tank, a first circulation pump, an auxiliary heater, a low-temperature storage tank, a second circulation pump and a condenser. The high-temperature storage tank, the first circulation pump, the heat storage medium side of the auxiliary heater, the low-temperature storage tank, the second circulation pump and the cooler are connected in sequence;

[0011] The power generation system is used for conventional cycle power generation and energy release cycle power generation, and includes a main compressor, a low-temperature recuperator, a high-temperature recuperator, a main heater, a turbine, a recompressor, a gas cooler, a cooling tower, and a circulation pump. The turbine is connected to a generator. The outlet of the main compressor is divided into a main preheating branch and an auxiliary preheating branch through a first three-way valve. The main preheating branch is sequentially connected to the high-pressure side inlet of the low-temperature recuperator and the high-pressure side inlet of the high-temperature recuperator. The auxiliary preheating branch is sequentially connected to the working medium side inlet of the auxiliary heater and the high-pressure side inlet of the high-temperature recuperator. The fluids in the main preheating branch and the auxiliary preheating branch are mixed at the high-pressure side inlet of the high-temperature recuperator. The outlet of the high-pressure side of the high-temperature recuperator is sequentially connected to the main heater, the turbine, the low-pressure side inlet of the high-temperature recuperator, and the low-pressure side inlet of the low-temperature recuperator. The outlet of the low-pressure side of the low-temperature recuperator is divided into a recompression branch and a main cooling branch through a second three-way valve. The recompression branch is sequentially connected to the inlet of the recompressor and the high-pressure side inlet of the high-temperature recuperator. The main cooling branch is sequentially connected to the working medium side of the gas cooler and the main compressor, thus forming a closed power cycle. The gas cooler dissipates heat to the cooling cycle circuit. The cooling medium circuit includes a gas cooler, a cooling water tower, a circulation pump, and a heater. The outlet of the cooling medium side of the gas cooler is divided into a first cooling cycle branch and a second cooling cycle branch through a third three-way valve. The first cooling cycle branch is sequentially connected to the cooling water tower, the circulation pump, and the gas cooler. The second cooling cycle branch is connected to the cooling medium side of the heater, the circulation pump, and the cooling medium side of the gas cooler. The two branches converge at the inlet of the circulation pump.

[0012] Preferably, the charging power generation system and the power generation system use supercritical carbon dioxide as the working medium, and the circulating heat storage medium of the heat storage system uses heat-conducting oil.

[0013] The method includes a conventional mode, an energy storage mode, an energy release mode, and a peak shaving method;

[0014] In the conventional mode, the power generation system operates independently in the form of a recompression cycle without interacting with the charging power generation system and the heat storage system;

[0015] Under the operation of the conventional mode, after the working medium at the outlet of the low-pressure side of the low-temperature recuperator is shunted, the main part flows through the main cooling branch, releases heat to the cooling medium circuit through the gas cooler, and the cooled working medium is compressed and heated by the main compressor, flows through the high-pressure side inlet of the low-temperature recuperator, and exchanges heat with the working medium on the low-pressure side. A small part of the working medium flows through the recompression branch, is directly compressed by the recompressor, and then is mixed with the working medium on the main path, and sequentially flows through the high-pressure side of the high-temperature recuperator and the main heater to absorb heat. The high-temperature and high-pressure working medium expands and does work through the turbine, and sequentially flows through the high-temperature recuperator and the low-temperature recuperator to release heat and cool to the high-pressure side, completing the positive power generation cycle process.

[0016] In the cooling medium circulation, the low-temperature cooling medium is boosted by a circulation pump and then flows into the gas cooler to absorb heat from the working fluid side. Subsequently, it is controlled by a third three-way valve to flow through the first cooling circulation branch and is cooled down to the environment through a cooling water tower.

[0017] In the energy storage mode, the charging subsystem and the power generation subsystem operate simultaneously, and the power generation subsystem provides power to the compressor.

[0018] Under the operation of the energy storage mode, the power generation cycle process of the power generation subsystem is the same as that in the conventional mode.

[0019] The working fluid of the charging subsystem is compressed and heated by the compressor, then flows into the cooler to release heat to the low-temperature heat storage medium. The cooled working fluid flows into the expander to expand and do work. The low-temperature and low-pressure working fluid enters the heater to absorb heat and increase in temperature, and then flows into the compressor to complete the charging reverse cycle process.

[0020] In the heat storage subsystem, the low-temperature heat storage medium in the low-temperature storage tank is driven by a second circulation pump, flows through the heat storage medium side of the cooler to absorb heat and increase in temperature, and then is stored in the high-temperature storage tank to complete the heat storage process.

[0021] In the cooling medium circulation, the low-temperature cooling medium is boosted by a circulation pump and then flows into the gas cooler to absorb heat from the working fluid side. Subsequently, it is controlled by a third three-way valve to flow through the second cooling circulation branch and releases heat to cool down the working fluid of the charging subsystem through a cold heater.

[0022] In the energy release mode, the re-compressor of the power generation subsystem is cut off from operation. The first three-way valve simultaneously opens the main preheating branch and the auxiliary preheating branch and adjusts the ratio. The first circulation pump of the heat storage subsystem operates, and the auxiliary heater completes the auxiliary preheating of the branch.

[0023] Under the operation of the energy release mode, the working fluid at the outlet of the main compressor is split. The main part flows through the main preheating branch and is heated by the low-temperature recuperator. Another part of the working fluid flows through the auxiliary preheating branch and absorbs the heat of the high-temperature heat storage medium in the auxiliary heater. Subsequently, the two-way working fluids complete the confluence, successively flow through the high-temperature recuperator and the main heater to absorb heat. The high-temperature and high-pressure working fluid expands and does work through the turbine, successively flows through the high-temperature recuperator and the low-temperature recuperator to complete the regenerative process, and then flows through the gas cooler to release heat to the cooling medium. The cooled working fluid is compressed and boosted by the main compressor to complete the power generation cycle process.

[0024] In the heat storage subsystem, the high-temperature heat storage medium in the high-temperature storage tank is driven by a first circulation pump, flows through the auxiliary heater to release heat and cool down, and then is stored in the low-temperature storage tank to complete the heat release process.

[0025] In the cooling medium circulation, the low-temperature cooling medium is boosted by a circulation pump and then flows into the gas cooler to absorb heat from the working fluid side. Subsequently, it is controlled by the third three-way valve to flow through the first cooling circulation branch and is cooled down to the environment through a cooling water tower.

[0026] The peak shaving method includes:

[0027] During the peak electricity consumption period, the system switches to the normal mode of operation, and the power generation subsystem outputs rated load power.

[0028] During the low electricity consumption period or the new energy explosion period, the system switches to the energy storage operation mode. The charging subsystem consumes part of the power of the power generation subsystem, generates low-grade heat energy, and stores it in the high-temperature storage tank, reducing the overall net output of the system.

[0029] During the peak electricity consumption period, the system switches to the energy release operation mode. The recompressor of the power generation subsystem is cut off from operation. The high-temperature heat storage medium releases heat in the auxiliary heater and preheats part of the working fluid in the branch, increasing the net output of the power generation subsystem.

[0030] The beneficial effects of the present invention are:

[0031] The present invention is coupled by a power generation subsystem, a heat storage subsystem, and a charging subsystem. Through the compression power consumption of the charging subsystem, the system output is reduced, heat is produced and stored, and the energy storage process is completed. By cutting off the recompression process of the power generation subsystem and using the high-temperature heat storage to assist in heating the working fluid in the branch, the system output is increased, and the energy release process is completed. The storage-release process of energy relies on the internal process reorganization and deep coupling of the cycle, has a higher round-trip efficiency, does not require additional auxiliary heat sources or waste heat resources, and has universality for high-temperature heat sources such as coal-based, nuclear energy, and solar thermal. Description of the Drawings

[0032] Figure 1 It is a schematic flow diagram of an electric energy storage coupling system based on a positive and reverse supercritical carbon dioxide cycle

[0033] In the figure: Among them, 1 is the charging subsystem; 2 is the heat storage subsystem; 3 is the power generation subsystem; 11 is the compressor; 12 is the cooler; 13 is the expander; 14 is the heater; 21 is the high-temperature storage tank; 22 is the first circulation pump; 23 is the auxiliary heater; 24 is the low-temperature storage tank; 25 is the second circulation pump; 31 is the main compressor; 32 is the low-temperature recuperator; 33 is the high-temperature recuperator; 34 is the main heater; 35 is the turbine; 36 is the recompressor; 37 is the gas cooler; 38 is the cooling tower; 39 is the circulation pump; 301 is the first three-way valve; 302 is the second three-way valve; 303 is the third three-way valve. Detailed Embodiments

[0034] Example 1

[0035] An electrical energy storage coupling system based on a positive and reverse supercritical carbon dioxide cycle. The system includes a charging subsystem 1, a heat storage subsystem 2, and a power generation subsystem 3, and has the function of relying on the internal energy interaction, storage, and release of the subsystems to adjust the power load output of the system. Among them:

[0036] The charging subsystem 1 is used to absorb the excess power of the power generation subsystem 3 and convert it into low-grade heat energy. It includes a compressor 11, a cooler 12, an expander 13, and a heater 14. The outlet of the compressor 11 is connected to the inlet of the working fluid side of the cooler 12, the outlet of the working fluid side of the cooler 12 is connected to the inlet of the expander 13, the outlet of the expander 13 is connected to the inlet of the working fluid side of the heater 14, and the outlet of the working fluid side of the heater 14 is connected to the inlet of the compressor 11;

[0037] The heat storage subsystem 2 is used to intermittently store the heat energy generated by the charging subsystem 1 and provide additional heat energy to the power generation subsystem 3. It includes a high-temperature storage tank 21, a first circulation pump 22, an auxiliary heater 23, a low-temperature storage tank 24, a second circulation pump 25, and a condenser 12. The high-temperature storage tank 21, the first circulation pump 22, the heat storage medium side of the auxiliary heater 23, the low-temperature storage tank 24, the second circulation pump 25, and the cooler 12 are connected in sequence;

[0038] The power generation subsystem 3 is used for conventional cycle power generation and energy release cycle power generation, and includes a main compressor 31, a low-temperature recuperator 32, a high-temperature recuperator 33, a main heater 34, a turbine 35, a recompressor 36, a gas cooler 37, a cooling tower 38, and a circulation pump 39. The turbine 35 is connected to a generator. The outlet of the main compressor 31 is divided into a main preheating branch and an auxiliary preheating branch through a first three-way valve 301. The main preheating branch is sequentially connected to the high-pressure side inlet of the low-temperature recuperator 32 and the high-pressure side inlet of the high-temperature recuperator 33. The auxiliary preheating branch is sequentially connected to the working medium side inlet of the auxiliary heater 23 and the high-pressure side inlet of the high-temperature recuperator 33. The fluids in the main preheating branch and the auxiliary preheating branch are mixed at the high-pressure side inlet of the high-temperature recuperator 33. The high-pressure side outlet of the high-temperature recuperator 33 is sequentially connected to the main heater 34, the turbine 35, the low-pressure side inlet of the high-temperature recuperator 33, and the low-pressure side inlet of the low-temperature recuperator 32. The low-pressure side outlet of the low-temperature recuperator 32 is divided into a recompression branch and a main cooling branch through a second three-way valve 302. The recompression branch is sequentially connected to the inlet of the recompressor 36 and the high-pressure side inlet of the high-temperature recuperator 33. The main cooling branch is sequentially connected to the working medium side of the gas cooler 37 and the main compressor 31, thereby forming a closed power cycle. The gas cooler 37 dissipates heat to the cooling circulation loop; the cooling medium loop includes the gas cooler 37, the cooling water tower 38, the circulation pump 39, and the heater 14. The cooling medium side outlet of the gas cooler 37 is divided into a first cooling circulation branch and a second cooling circulation branch through a third three-way valve 303. The first cooling circulation branch is sequentially connected to the cooling water tower 38, the circulation pump 39, and the gas cooler 37. The second cooling circulation branch is connected to the cooling medium side of the heater 14, the circulation pump 39, and the cooling medium side of the gas cooler 37. The two branches converge at the inlet of the circulation pump 39.

[0039] The charging subsystem 1 and the power generation subsystem 3 use supercritical carbon dioxide as the working medium, and the heat storage subsystem 2 circulates the heat storage medium using heat-conducting oil.

[0040] The method includes a conventional mode, an energy storage mode, an energy release mode, and a peak shaving method;

[0041] In the conventional mode, the power generation subsystem 3 operates independently in the form of a recompression cycle without interacting with the charging subsystem 1 and the heat storage subsystem 2;

[0042] Under normal mode operation, after the working fluid at the outlet of the low-pressure side of the low-temperature recuperator 32 is split, the main part flows through the main cooling branch, releases heat to the cooling medium circuit through the gas cooler 37, the cooled working fluid is compressed and heated up by the main compressor 31, flows through the high-pressure side inlet of the low-temperature recuperator 32, and exchanges heat with the working fluid on the low-pressure side. A small part of the working fluid flows through the recompression branch, is directly compressed by the re-compressor 36, then mixes with the working fluid on the main path, successively flows through the high-pressure side of the high-temperature recuperator 33 and the main heater 34 to absorb heat, the high-temperature and high-pressure working fluid expands and does work through the turbine 35, and successively flows through the high-temperature recuperator 33 and the low-temperature recuperator 32 to release heat and cool on the high-pressure side, completing the positive power generation cycle process;

[0043] In the cooling medium circulation, the low-temperature cooling medium is boosted by the circulation pump 39 and then flows into the gas cooler 37 to absorb heat from the working fluid side. Subsequently, it is controlled by the third three-way valve 303 to flow through the first cooling circulation branch and is cooled down to the environment through the cooling water tower 38;

[0044] In the energy storage mode, the charging subsystem 1 and the power generation subsystem 3 operate simultaneously, and the power generation subsystem 3 supplies power to the compressor 11;

[0045] Under energy storage mode operation, the power generation cycle process of the power generation subsystem 3 is the same as the power generation cycle process described under normal mode;

[0046] The working fluid of the charging subsystem 1 is compressed and heated up by the compressor 11, then flows into the cooler 12 to release heat to the low-temperature heat storage medium, the cooled working fluid flows into the expander 13 to expand and do work, the low-temperature and low-pressure working fluid enters the heater 14 to absorb heat and heat up, and then flows into the compressor 11, completing the charging reverse cycle process;

[0047] In the heat storage subsystem 2, the low-temperature heat storage medium in the low-temperature storage tank 24 is driven by the second circulation pump 25, flows through the heat storage medium side of the cooler 12 to absorb heat and heat up, and then is stored in the high-temperature storage tank 21, completing the heat storage process;

[0048] In the cooling medium circulation, the low-temperature cooling medium is boosted by the circulation pump 39 and then flows into the gas cooler 37 to absorb heat from the working fluid side. Subsequently, it is controlled by the third three-way valve 303 to flow through the second cooling circulation branch and releases heat and cools down to the working fluid of the charging subsystem through the cold heater 14;

[0049] In the energy release mode, the re-compressor 36 of the power generation subsystem 3 is cut off from operation, the first three-way valve 301 simultaneously opens the main preheating branch and the auxiliary preheating branch and adjusts the ratio, and the first circulation pump 22 of the heat storage subsystem 2 operates, and the auxiliary heater 23 completes the auxiliary preheating of the branch;

[0050] Under the exothermic mode of operation, the working fluid at the outlet of the main compressor 31 is split. The main part flows through the main preheating branch and is heated by the low-temperature recuperator. Another part of the working fluid flows through the auxiliary preheating branch, absorbs the heat of the high-temperature heat storage medium in the auxiliary heater 23, and then the two streams of working fluid merge, and successively flow through the high-temperature recuperator 33 and the main heater 34 to absorb heat. The high-temperature and high-pressure working fluid expands and does work through the turbine 35, successively flows through the high-temperature recuperator 33 and the low-temperature recuperator 32 to complete the regenerative process, and then flows through the gas cooler 37 to release heat to the cooling medium. The cooled working fluid is compressed and boosted by the main compressor 31 to complete the power generation cycle process;

[0051] In the heat storage subsystem 2, the high-temperature heat storage medium in the high-temperature storage tank 21 is driven by the first circulation pump 22, flows through the auxiliary heater 23 to release heat and cool down, and then is stored in the low-temperature storage tank 24 to complete the heat release process;

[0052] In the cooling medium circulation, the low-temperature cooling medium is boosted by the circulation pump 39 and then flows into the gas cooler 37 to absorb heat from the working fluid side. Subsequently, it is controlled by the third three-way valve 303 to flow through the first cooling circulation branch and is cooled down to the environment by the cooling water tower 38;

[0053] The peak shaving method includes:

[0054] During the peak period of power consumption, the system switches to the conventional mode of operation, and the power generation subsystem 3 outputs rated load power;

[0055] During the low valley period of power consumption or the new energy outbreak period, the system switches to the energy storage operation mode. The charging subsystem 1 consumes part of the power of the power generation subsystem 3, generates low-grade heat energy, and stores it in the high-temperature storage tank 21 to reduce the overall net output of the system. During the peak period of power consumption, the system switches to the exothermic operation mode, the recompressor 36 of the power generation subsystem 3 is cut off from operation, and the high-temperature heat storage medium releases heat in the auxiliary heater 23 and preheats part of the working fluid in the preheating branch to increase the net output of the power generation subsystem.

[0056] Among them, in the conventional mode of operation: after the working fluid at the low-pressure side outlet of the low-temperature recuperator 32 is split, the main part flows through the main cooling branch and releases heat to the cooling medium circuit through the gas cooler 37. The cooled working fluid is compressed and heated by the main compressor 31, flows through the high-pressure side inlet of the low-temperature recuperator 32, and exchanges heat with the working fluid on the low-pressure side. A small part of the working fluid flows through the recompression branch and is directly compressed by the recompressor 36, and then mixes with the working fluid on the main path, and successively flows through the high-temperature recuperator 33 and the main heater 34 to absorb heat. The high-temperature and high-pressure working fluid expands and does work through the turbine 35, and successively flows through the high-temperature recuperator 33 and the low-temperature recuperator 32 to release heat and cool down to the low-temperature side to complete the power generation (positive) cycle process;

[0057] 30% of the working fluid by mass flows through the recompression branch, and 70% of the working fluid by mass flows through the main cooling branch;

[0058] The working medium temperature at the turbine inlet of the power generation subsystem ≥ 550 °C;

[0059] In the cooling medium circulation, the third three-way valve 303 controls the opening of the first cooling circulation branch and the closing of the second cooling circulation branch. The low-temperature cooling medium is boosted by the circulation pump 39 and then flows into the gas cooler 37 to absorb heat from the working medium side, and then is cooled by the cooling water tower 38 to the environment.

[0060] Energy storage mode operation: The charging subsystem 1 and the power generation subsystem 3 operate simultaneously, and the power generation subsystem 3 supplies power to the compressor 11;

[0061] The power generation cycle process of the power generation subsystem 3 is the same as that described in the normal mode;

[0062] The working medium of the charging subsystem 1 is compressed and heated by the compressor 11, then flows into the cooler 12 to release heat to the low-temperature heat storage medium, the cooled working medium flows into the expander 13 to do work by expansion, the low-temperature and low-pressure working medium enters the heater 14 to absorb heat and heat up, and then flows into the compressor 11 to complete the charging (reverse) cycle process.

[0063] The working medium temperature at the outlet of the charging subsystem compressor is 150 to 250 °C;

[0064] In the heat storage subsystem 2, the low-temperature heat storage medium in the low-temperature storage tank 24 is driven by the second circulation pump 25, flows through the cooler 12 to absorb heat and heat up, and then is stored in the high-temperature storage tank 21 to complete the heat storage process;

[0065] In the cooling medium circulation, the third three-way valve 303 controls the opening of the second cooling circulation branch. The low-temperature cooling medium is boosted by the circulation pump 39 and then flows into the gas cooler 37 to absorb heat from the working medium side, and then releases heat to the working medium of the charging subsystem through the cold heater 14 to cool down.

[0066] Energy release mode operation: The recompressor 36 of the power generation subsystem 3 is cut off from operation. The first three-way valve 301 simultaneously opens the main preheating branch and the auxiliary preheating branch and adjusts the ratio. The first circulation pump 22 of the heat storage subsystem 2 operates, and the auxiliary heater 23 completes the auxiliary preheating of the branch;

[0067] The working medium at the outlet of the main compressor 31 is split. The main part flows through the main preheating branch and is heated by the low-temperature recuperator, and the other part of the working medium flows through the auxiliary preheating branch and absorbs the heat of the high-temperature heat storage medium in the auxiliary heater 23. Then the two-way working media are combined, and then flow through the high-temperature recuperator 33 and the main heater 34 to absorb heat in sequence. The high-temperature and high-pressure working medium expands and does work through the turbine 35, and then flows through the high-temperature recuperator 33 and the low-temperature recuperator 32 to complete the regenerative process, and then flows through the gas cooler 37 to release heat to the cooling medium. The cooled working medium is compressed and boosted by the main compressor (31) to complete the power generation cycle process;

[0068] Preferably, 30% of the working medium by mass flows through the auxiliary heating branch, and 70% of the working medium by mass flows through the main preheating branch;

[0069] In the heat storage subsystem 2, the high-temperature heat storage medium in the high-temperature storage tank 21 is driven by the first circulation pump 22, flows through the auxiliary heater 23 to release heat and cool down, and then is stored in the low-temperature storage tank 24 to complete the heat release process;

[0070] In the cooling medium circulation, the third three-way valve 303 controls the opening of the first cooling circulation branch. The low-temperature cooling medium is boosted by the circulation pump 39 and then flows into the gas cooler 37 to absorb heat from the working medium side, and then is cooled down to the environment through the cooling water tower 38.

[0071] During the peak electricity consumption period, the system switches to the conventional mode of operation, and the power generation subsystem outputs rated load power;

[0072] During the low electricity consumption period or the new energy outbreak period, the system switches to the energy storage operation mode. The charging subsystem 1 consumes part of the power of the power generation subsystem 3, generates low-grade heat energy, and stores it in the high-temperature storage tank, reducing the overall net output of the system;

[0073] During the peak electricity consumption period, the system switches to the heat release operation mode. The recompressor 36 of the power generation subsystem 3 is cut off from operation. The high-temperature heat storage medium releases heat in the auxiliary heater 23 and preheats part of the working medium in the preheating branch, increasing the net output of the power generation subsystem.

[0074] Under the condition that the key parameters of the positive cycle of the system of the present invention remain basically unchanged, the active regulation of the power generation output can be realized by changing the cycle process.

[0075] By the charging subsystem 1 consuming excess power, generating low-grade heat energy, and storing it in the heat storage subsystem 2, low-temperature (about 200 °C) atmospheric heat storage has a simple system structure and good technical economy.

[0076] By cutting off the high-energy-consuming recompression process, the effect of system power improvement is achieved without adding power units and simplifying the system.

[0077] There are significant differences in the working temperature levels between the reverse cycle and the positive cycle. During the charge and discharge processes, the low-grade heat energy can be upgraded and utilized by leveraging the high-efficiency power cycle, which can effectively improve the round-trip efficiency of the energy storage and release processes.

[0078] The system only relies on the internal process reorganization and deep coupling of the cycle, without relying on additional auxiliary heat sources or waste heat resources, and has universality for high-temperature heat sources such as coal-based, nuclear energy, and solar thermal.

[0079] The above embodiments are only used to illustrate the present invention rather than to limit the technical solutions described in the present invention. Although the present specification has described the present invention in detail with reference to the above respective embodiments, the present invention is not limited to the above specific implementation manners. Therefore, any modification or equivalent replacement of the present invention; and all technical solutions and their improvements that do not depart from the spirit and scope of the invention are covered by the scope of the claims of the present invention.

Claims

1. An electrical energy storage and coupling system based on a positive and reverse supercritical carbon dioxide cycle, characterized in that The system includes a charging subsystem (1), a heat storage subsystem (2), and a power generation subsystem (3); The charging subsystem (1) is used to absorb the excess power of the power generation subsystem (3) and convert it into low-grade heat energy. It includes a compressor (11), a cooler (12), an expander (13), and a heater (14). The outlet of the compressor (11) is connected to the inlet of the working fluid side of the cooler (12), the outlet of the working fluid side of the cooler (12) is connected to the inlet of the expander (13), the outlet of the expander (13) is connected to the inlet of the working fluid side of the heater (14), and the outlet of the working fluid side of the heater (14) is connected to the inlet of the compressor (11); The heat storage subsystem (2) is used to intermittently store the heat energy generated by the charging subsystem (1) and provide additional heat energy to the power generation subsystem (3). It includes a high-temperature storage tank (21), a first circulation pump (22), an auxiliary heater (23), a low-temperature storage tank (24), a second circulation pump (25), and a condenser (12). The high-temperature storage tank (21), the first circulation pump (22), the heat storage medium side of the auxiliary heater (23), the low-temperature storage tank (24), the second circulation pump (25), and the cooler (12) are sequentially connected in a cycle; The power generation subsystem (3) is used for conventional cycle power generation and energy release cycle power generation, and includes a main compressor (31), a low-temperature recuperator (32), a high-temperature recuperator (33), a main heater (34), a turbine (35), a recompressor (36), a gas cooler (37), a cooling tower (38) and a circulation pump (39). The turbine (35) is connected to a generator. The outlet of the main compressor (31) is divided into a main preheating branch and an auxiliary preheating branch through a first three-way valve (301). The main preheating branch is sequentially connected to the high-pressure side inlet of the low-temperature recuperator (32) and the high-pressure side inlet of the high-temperature recuperator (33). The auxiliary preheating branch is sequentially connected to the working medium side inlet of the auxiliary heater (23) and the high-pressure side inlet of the high-temperature recuperator (33). The fluids in the main preheating branch and the auxiliary preheating branch are mixed at the high-pressure side inlet of the high-temperature recuperator (33). The high-pressure side outlet of the high-temperature recuperator (33) is sequentially connected to the main heater (34), the turbine (35), the low-pressure side inlet of the high-temperature recuperator (33), and the low-pressure side inlet of the low-temperature recuperator (32). The low-pressure side outlet of the low-temperature recuperator (32) is divided into a recompression branch and a main cooling branch through a second three-way valve (302). The recompression branch is sequentially connected to the inlet of the recompressor (36) and the high-pressure side inlet of the high-temperature recuperator (33). The main cooling branch is sequentially connected to the working medium side of the gas cooler (37) and the main compressor (31), thus forming a closed power cycle. The gas cooler (37) dissipates heat to the cooling cycle loop. The cooling medium loop includes the gas cooler (37), the cooling water tower (38), the circulation pump (39), and the heater (14). The cooling medium side outlet of the gas cooler (37) is divided into a first cooling cycle branch and a second cooling cycle branch through a third three-way valve (303). The first cooling cycle branch is sequentially connected to the cooling water tower (38), the circulation pump (39) and the gas cooler (37). The second cooling cycle branch is connected to the cooling medium side of the heater (14), the circulation pump (39) and the cooling medium side of the gas cooler (37). The two branches converge at the inlet of the circulation pump (39).

2. The electro-storage coupling system based on the forward and reverse supercritical carbon dioxide cycle according to claim 1, wherein The charging subsystem (1) and the power generation subsystem (3) use supercritical carbon dioxide as the working medium, and the heat storage medium of the heat storage subsystem (2) circulating heat storage adopts heat-conducting oil.

3. A method for an electrical energy storage and coupling system based on a positive and negative supercritical carbon dioxide cycle according to any one of claims 1-2, characterized in that the method includes a conventional mode, an energy storage mode, an energy release mode and a peak shaving method; in the conventional mode, the power generation subsystem (3) operates independently in the form of a recompression cycle without interacting with the charging subsystem (1) and the heat storage subsystem (2). In the normal mode of operation, after the working medium at the outlet of the low-pressure side of the low-temperature recuperator (32) is divided, the main part flows through the main cooling branch, releases heat to the cooling medium circuit through the gas cooler (37), the cooled working medium is compressed and heated up by the main compressor (31), flows through the high-pressure side inlet of the low-temperature recuperator (32), and exchanges heat with the working medium on the low-pressure side. A small part of the working medium flows through the recompression branch, is directly compressed by the recompression compressor (36), and then mixes with the working medium on the main path, and successively flows through the high-pressure side of the high-temperature recuperator (33) and the main heater (34) to absorb heat. The high-temperature and high-pressure working medium expands and does work through the turbine (35), and successively flows through the high-temperature recuperator (33) and the low-temperature recuperator (32) to release heat and cool the high-pressure side, completing the positive power generation cycle process; In the cooling medium cycle, the low-temperature cooling medium is boosted by the circulation pump (39) and then flows into the gas cooler (37) to absorb heat from the working medium side, and then is controlled by the third three-way valve (303) to flow through the first cooling circulation branch, and is cooled down to the environment through the cooling water tower (38); In the energy storage mode, the charge sub-system (1) and the power generation sub-system (3) operate simultaneously, and the power generation sub-system (3) supplies power to the compressor (11); In the energy storage mode of operation, the power generation cycle process of the power generation sub-system (3) is the same as the power generation cycle process described in the normal mode; After the working medium of the charge sub-system (1) is compressed and heated up by the compressor (11), it flows into the cooler (12) to release heat to the low-temperature heat storage medium, the cooled working medium flows into the expander (13) to expand and do work, the low-temperature and low-pressure working medium enters the heater (14) to absorb heat and heat up, and then flows into the compressor (11), completing the reverse charging cycle process; In the heat storage sub-system (2), the low-temperature heat storage medium in the low-temperature storage tank (24) is driven by the second circulation pump (25), flows through the heat storage medium side of the cooler (12) to absorb heat and heat up, and then is stored in the high-temperature storage tank (21), completing the heat storage process; In the cooling medium cycle, the low-temperature cooling medium is boosted by the circulation pump (39) and then flows into the gas cooler (37) to absorb heat from the working medium side, and then is controlled by the third three-way valve (303) to flow through the second cooling circulation branch, and releases heat and cools down to the working medium of the charge sub-system through the cold heater (14); In the energy release mode, the recompression compressor (36) of the power generation sub-system (3) is cut off from operation, the first three-way valve (301) simultaneously opens the main preheating branch and the auxiliary preheating branch and adjusts the ratio, and the first circulation pump (22) of the heat storage sub-system (2) operates, and the auxiliary heater (23) completes the auxiliary preheating of the branch; Under the energy release mode of operation, the working fluid at the outlet of the main compressor (31) is split. The main part flows through the main preheating branch and is heated by the low-temperature recuperator. Another part of the working fluid flows through the auxiliary preheating branch, absorbs the heat of the high-temperature heat storage medium in the auxiliary heater (23), and then the two streams of working fluid merge and successively flow through the high-temperature recuperator (33) and the main heater (34) to absorb heat. The high-temperature and high-pressure working fluid expands and does work through the turbine (35), successively flows through the high-temperature recuperator (33) and the low-temperature recuperator (32) to complete the regenerative process, and then flows through the gas cooler (37) to release heat to the cooling medium. The cooled working fluid is compressed and boosted by the main compressor (31) to complete the power generation cycle process; In the heat storage subsystem (2), the high-temperature heat storage medium in the high-temperature storage tank (21) is driven by the first circulation pump (22), flows through the auxiliary heater (23) to release heat and cool down, and then is stored in the low-temperature storage tank (24) to complete the heat release process; In the cooling medium circulation, the low-temperature cooling medium is boosted by the circulation pump (39) and flows into the gas cooler (37) to absorb heat from the working fluid side, and then is controlled by the third three-way valve (303) to flow through the first cooling circulation branch and is cooled down to the environment by the cooling water tower (38); The peak shaving method includes: During the peak period of electricity consumption, the system switches to the conventional mode of operation, and the power generation subsystem (3) outputs rated load power; During the low period of electricity consumption or the period of new energy outbreak, the system switches to the energy storage operation mode. The charge subsystem (1) consumes part of the power of the power generation subsystem (3), generates low-grade heat energy, and stores it in the high-temperature storage tank (21), reducing the overall net output of the system. During the peak period of electricity consumption, the system switches to the energy release operation mode, the re-compressor (36) of the power generation subsystem (3) is cut off from operation, and the high-temperature heat storage medium releases heat in the auxiliary heater (23) to preheat part of the working fluid in the preheating branch, increasing the net output of the power generation subsystem.

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