Electric storage coupling system and method based on positive and negative supercritical carbon dioxide circulation

Abstract

The invention relates to an electric storage coupling system and method based on positive and negative supercritical carbon dioxide circulation, and belongs to the technical field of physical energy storage power generation. The electric storage coupling system based on positive and negative supercritical carbon dioxide circulation comprises a charging subsystem, a power generation subsystem and a heat storage subsystem. The method comprises a conventional mode, an energy storage mode, an energy release mode and a peak regulation method. The power generation subsystem, the heat storage subsystem and the charging subsystem are coupled, consumed power is compressed through the charging subsystem, system output is reduced, stored heat is produced, the energy storage process is completed, the recompression process of the power generation subsystem is cut off, branch working media are heated in an auxiliary mode through high-temperature heat storage, system output is increased, and the energy release process is completed. The energy storage-release process depends on reforming and deep coupling of a circulation internal process, has higher round-trip efficiency, does not need to depend on additional auxiliary heat sources or waste heat resources, and has universality for high-temperature heat sources such as coal-based heat sources, nuclear energy heat sources and photo-thermal heat sources.

Description

Technical Field

[0001] The present invention relates to the technical field of physical energy storage and power generation, and in particular to an energy storage coupling system and method based on forward and reverse supercritical carbon dioxide cycles. Background Art

[0002] The proportion of green renewable energy power in the future power system will increase significantly. However, photovoltaic, wind power and other new energy power generation are volatile, intermittent and unpredictable. High proportion of new energy power generation faces the problems of grid connection, consumption and dispatch. The difficulty of the power system regulation capacity to adapt to the demand for large-scale grid connection of new energy has become one of the bottlenecks restricting my country's energy transformation.

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

[0004] Energy storage can effectively improve the capacity of flexible peak regulation and is a good choice to promote the development of new power systems. The coupled operation of energy storage system and thermal power generation system can effectively eliminate the peak-valley difference, smooth the load fluctuation, and improve the operation flexibility of the power supply side to a certain extent. In the coupled system of thermal power and energy storage, energy storage involves many methods such as compressed gas energy storage, physical heat storage and heat pump power 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, the pressure changes and throttling losses in the storage and release process usually require pressurized storage, which affects the economy of the system. The configuration of the power cycle and physical heat storage coupling system is relatively simple, and heat storage mainly comes from two methods: direct electric heating and steam extraction heat storage; electric heating does not affect the steam-water cycle of the power plant, but there is a typical problem of "high quality and low use" of energy, which affects the cycle efficiency. The stored heat can be directly used for heat, but the application scenario or demand is limited and the unit output cannot be increased. Heat pump power storage, namely Carnot battery, is a new type of large-scale energy storage method that is not restricted by geographical conditions and has no pressure storage container, and has broad development prospects. When the heat pump stores electricity in an independent cycle, the working temperatures of the forward and reverse cycles are equivalent. In addition, due to irreversible factors such as physical properties and heat transfer temperature differences, its round-trip efficiency is generally low.

[0005] In the past, the coupling and matching of thermodynamic cycle and energy storage cycle was usually ignored in energy storage systems, resulting in energy throttling loss or high quality and low utilization in the storage and release process. Summary of the invention

[0006] In order to solve the above problems, the present invention provides an electricity storage coupling system and method based on forward and reverse supercritical carbon dioxide cycles. During the low electricity consumption period or the explosive period of new energy power generation, the charging subsystem is used to consume part of the electricity to produce low-grade thermal energy and store it in the heat storage subsystem; when the external power is insufficient or the electricity consumption is at a peak, 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 branch working fluid, thereby reducing the self-consumption of the power generation subsystem and increasing the net output; during the peak period of electricity consumption, the power generation subsystem operates independently and outputs the rated power with high efficiency.

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

[0008] An electric storage coupling system based on a forward 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 regulating the power load output of the system by relying on the energy interaction and storage and release within the subsystems, wherein:

[0009] The charging subsystem is used to consume the excess power of the power generation subsystem and convert it into low-grade thermal energy, including 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 generated by the charging subsystem and provide additional heat energy to the power generation subsystem, including a high-temperature storage tank, a first circulation pump, an auxiliary heater, a low-temperature storage tank, a second circulation pump and a condenser, wherein 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 subsystem is used for conventional cycle power generation and energy release cycle power generation, including a main compressor, a low-temperature regenerator, a high-temperature regenerator, a main heater, a turbine, a recompressor, a gas cooler, a cooling tower, and a circulating 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 connected to the high-pressure side inlet of the low-temperature regenerator and the high-pressure side inlet of the high-temperature regenerator in sequence. The auxiliary preheating branch is connected to the working fluid side inlet of the auxiliary heater and the high-pressure side inlet of the high-temperature regenerator in sequence. The main preheating branch and the auxiliary preheating branch fluid are mixed at the high-pressure side inlet of the high-temperature regenerator. The high-pressure side outlet of the high-temperature regenerator is connected to the main heater, the turbine, the low-pressure side inlet of the high-temperature regenerator, and the low-pressure side inlet of the low-temperature regenerator in sequence. The low-pressure side outlet of the low-temperature regenerator is divided into a recompression branch and a main cooling branch through a second three-way valve. The recompression branch is connected to the recompressor inlet and the high-pressure side inlet of the high-temperature regenerator in sequence. The main cooling branch is connected to the working fluid side of the gas cooler and the main compressor in sequence, thereby forming a closed power cycle. The gas cooler dissipates heat to the cooling circulation loop. 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 circulation branch and a second cooling circulation branch through a third three-way valve. The first cooling circulation branch is connected to the cooling water tower, the circulation pump, and the gas cooler in sequence. The second cooling circulation 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 subsystem and the power generation subsystem use supercritical carbon dioxide as the working fluid, and the heat storage subsystem uses heat transfer oil as the circulating heat storage medium.

[0013] The methods include conventional mode, energy storage mode, energy release mode and peak load regulation method;

[0014] In the conventional mode, the power generation subsystem operates independently in a recompression cycle and does not interact with the charging subsystem and the heat storage subsystem;

[0015] Under normal mode operation, after the working fluid at the low-pressure side outlet of the low-temperature regenerator is split, the main part flows through the main cooling branch and releases heat to the cooling medium circuit through the gas cooler. The cooled working fluid is compressed and heated by the main compressor, flows through the high-pressure side inlet of the low-temperature regenerator, 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. It is then mixed with the working fluid in the main circuit and flows through the high-pressure side of the high-temperature regenerator and the main heater in turn to absorb heat. The high-temperature and high-pressure working fluid expands through the turbine to do work, and flows through the high-temperature regenerator and the low-temperature regenerator in turn to release heat and cool to the high-pressure side, completing the positive cycle of power generation.

[0016] In the cooling medium circulation, the low-temperature cooling medium is pressurized by the circulation pump and flows into the gas cooler to absorb heat from the working medium side, and then controlled by the third three-way valve to flow through the first cooling circulation branch and cool down to the environment through the 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] In the energy storage mode, the power generation cycle of the power generation subsystem is consistent with the power generation cycle described in the normal 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 heat up, 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 the second circulation pump, flows through the heat storage medium side of the cooler, absorbs heat and heats up, 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 pressurized by the circulation pump and flows into the gas cooler to absorb heat from the working medium side, and then is controlled by the third three-way valve to flow through the second cooling circulation branch, and releases heat to the working medium of the charging subsystem through the cold heater to reduce the temperature;

[0022] In the energy release mode, the recompressor of the power generation subsystem is cut off and operated, 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 is operated, and the auxiliary heater completes the auxiliary preheating of the branch.

[0023] In the energy release mode, the working fluid at the outlet of the main compressor is split, with the main part flowing through the main preheating branch and heated by the low-temperature regenerator, and the other part flowing through the auxiliary preheating branch to absorb the heat of the high-temperature heat storage medium in the auxiliary heater. Then the two working fluids converge and flow through the high-temperature regenerator and the main heater in turn to absorb heat. The high-temperature and high-pressure working fluid expands through the turbine to do work, flows through the high-temperature regenerator and the low-temperature regenerator in turn to complete the reheating process, and then flows through the gas cooler to release heat to the cooling medium. The cooled working fluid is compressed and pressurized by the main compressor to complete the power generation cycle.

[0024] In the heat storage subsystem, the high-temperature heat storage medium in the high-temperature storage tank is driven by the first circulation pump, flows through the auxiliary heater to release heat and cool, 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 pressurized by the circulation pump and flows into the gas cooler to absorb heat from the working medium side, and then controlled by the third three-way valve to flow through the first cooling circulation branch and cool down to the environment through the cooling water tower;

[0026] Peak shaving methods include:

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

[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 electricity 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 peak electricity consumption, the system switches to the energy release operation mode, the recompressor of the power generation subsystem is cut off, and the high-temperature heat storage medium releases heat and preheats part of the branch working fluid in the auxiliary heater, thereby 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. The charging subsystem compresses the power consumption to reduce the system output and produces and stores heat to complete the energy storage process. The power generation subsystem recompression process and high-temperature heat storage auxiliary heating branch working fluid are cut off to increase the system output and complete the energy release process. The energy storage-release process relies on the internal process reforming and deep coupling of the cycle, has a higher round-trip efficiency, does not need to rely on additional auxiliary heat sources or waste heat resources, and is universal to high-temperature heat sources such as coal-based, nuclear energy, and solar thermal. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of the flow chart of the power storage coupling system based on the forward and reverse supercritical carbon dioxide cycle

[0033] In the figure: 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 regenerator; 33 is the high-temperature regenerator; 34 is the main heater; 35 is the turbine; 36 is the re-compressor; 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 DESCRIPTION

[0034] Example 1

[0035] A power storage coupling system based on a forward and reverse supercritical carbon dioxide cycle, the system comprises a charging subsystem 1, a heat storage subsystem 2 and a power generation subsystem 3, and has the function of regulating the power load output of the system by relying on the energy interaction and storage and release within the subsystems, wherein:

[0036] The charging subsystem 1 is used to consume the excess power of the power generation subsystem 3 and convert it into low-grade thermal energy, and 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, including 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, wherein 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, including a main compressor 31, a low-temperature regenerator 32, a high-temperature regenerator 33, a main heater 34, a turbine 35, a recompressor 36, a gas cooler 37, a cooling tower 38, and a circulating 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 connected to the high-pressure side inlet of the low-temperature regenerator 32 and the high-pressure side inlet of the high-temperature regenerator 33 in sequence, and the auxiliary preheating branch is connected to the working fluid side inlet of the auxiliary heater 23 and the high-temperature regenerator 33 in sequence. 3 high-pressure side inlet, the main preheating branch and the auxiliary preheating branch fluids complete mixing at the high-pressure side inlet of the high-temperature regenerator 33, the high-pressure side outlet of the high-temperature regenerator 33 is connected in sequence to the main heater 34, the turbine 35, the low-pressure side inlet of the high-temperature regenerator 33, and the low-pressure side inlet of the low-temperature regenerator 32, the low-pressure side outlet of the low-temperature regenerator 32 is divided into a recompression branch and a main cooling branch through a second three-way valve 302, the recompression branch is connected in sequence to the inlet of the recompressor 36 and the high-pressure side inlet of the high-temperature regenerator 33, the main cooling branch is connected in sequence 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 circuit includes a gas cooler 37, a cooling water tower 38, a circulation pump 39, and a 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 connected to the cooling water tower 38, the circulation pump 39 and the gas cooler 37 in sequence. 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 a working fluid, and the heat storage subsystem 2 uses heat transfer oil as a circulating heat storage medium.

[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 a recompression cycle and does not interact with the charging subsystem 1 and the heat storage subsystem 2;

[0042] Under normal mode operation, after the working fluid at the low-pressure side outlet of the low-temperature regenerator 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 regenerator 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 recompressor 36, and then mixed with the working fluid of the main circuit, and flows through the high-pressure side of the high-temperature regenerator 33 and the main heater 34 in turn to absorb heat. The high-temperature and high-pressure working fluid expands and performs work through the turbine 35, and flows through the high-temperature regenerator 33 and the low-temperature regenerator 32 in turn to release heat and cool to the high-pressure side, completing the positive cycle of power generation;

[0043] In the cooling medium circulation, the low-temperature cooling medium is pressurized by the circulation pump 39 and 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 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 provides power to the compressor 11;

[0045] In the energy storage mode, the power generation cycle of the power generation subsystem 3 is consistent with the power generation cycle described in the normal mode;

[0046] The working fluid of the charging subsystem 1 is compressed and heated by the compressor 11, and 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 to complete 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, absorbs heat and heats up, and then is stored in the high-temperature storage tank 21 to complete the heat storage process;

[0048] In the cooling medium circulation, the low-temperature cooling medium is pressurized by the circulation pump 39 and 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 to the working medium of the charging subsystem through the cold heater 14 to reduce the temperature;

[0049] In the energy release mode, the recompressor 36 of the power generation subsystem 3 is cut off, 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 is running, and the auxiliary heater 23 completes the auxiliary preheating of the branch;

[0050] In the energy release mode, the working fluid at the outlet of the main compressor 31 is split, with the main part flowing through the main preheating branch and heated by the low-temperature regenerator, and the other part flowing through the auxiliary preheating branch and absorbing the heat of the high-temperature heat storage medium in the auxiliary heater 23. Then, the two working fluids are merged and flow through the high-temperature regenerator 33 and the main heater 34 in turn to absorb heat. The high-temperature and high-pressure working fluid expands through the turbine 35 to do work, flows through the high-temperature regenerator 33 and the low-temperature regenerator 32 in turn to complete the reheating process, and then flows through the gas cooler 37 to release heat to the cooling medium. The cooled working fluid is compressed and pressurized by the main compressor 31 to complete the power generation cycle.

[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, 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 pressurized by the circulation pump 39 and 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 to the environment through the cooling water tower 38;

[0053] The peak shaving method comprises:

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

[0055] During the off-peak period of electricity consumption or the period of new energy explosion, the system switches to the energy storage operation mode, the charging subsystem 1 consumes part of the electricity of the power generation subsystem 3, generates low-grade thermal energy, and stores it in the high-temperature storage tank 21, thereby 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 recompressor 36 of the power generation subsystem 3 is cut off from operation, and the high-temperature heat storage medium completes the heat release and preheating of part of the branch working fluid in the auxiliary heater 23, thereby increasing the net output of the power generation subsystem.

[0056] Among them, the normal mode is operated as follows: after the working fluid at the low-pressure side outlet of the low-temperature regenerator 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 regenerator 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 recompressor 36, and then is mixed with the working fluid of the main circuit, flows through the high-temperature regenerator 33 and the main heater 34 in turn to absorb heat, the high-temperature and high-pressure working fluid expands through the turbine 35 to do work, flows through the high-temperature regenerator 33 and the low-temperature regenerator 32 in turn to release heat and cool to the low-temperature side, and completes 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 fluid temperature at the turbine inlet of the generator system is ≥550 °C;

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

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

[0061] The power generation cycle of the power generation subsystem 3 is consistent with the power generation cycle described in the conventional mode;

[0062] The working fluid of the charging subsystem 1 is compressed and heated by the compressor 11, and 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.

[0063] The outlet temperature of the working fluid 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] During the cooling medium circulation, the third three-way valve 303 controls the opening of the second cooling circulation branch, and the low-temperature cooling medium is pressurized by the circulation pump 39 and flows into the gas cooler 37 to absorb heat from the working fluid side, and then releases heat to the working fluid of the charging subsystem through the cold heater 14 to cool it down.

[0066] Energy release mode operation: the recompressor 36 of the power generation subsystem 3 is cut off and operated, 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 is operated, and the auxiliary heater 23 completes the auxiliary preheating of the branch;

[0067] The working fluid at the outlet of the main compressor 31 is split, with the main part flowing through the main preheating branch and being heated by the low-temperature regenerator, and the other part flowing through the auxiliary preheating branch and absorbing heat from the high-temperature heat storage medium in the auxiliary heater 23. The two paths of working fluid are then merged and flow through the high-temperature regenerator 33 and the main heater 34 in turn to absorb heat. The high-temperature and high-pressure working fluid is expanded by the turbine 35 to perform work, and flows through the high-temperature regenerator 33 and the low-temperature regenerator 32 in turn to complete the reheating process, and then flows through the gas cooler 37 to release heat to the cooling medium. The cooled working fluid is compressed and pressurized by the main compressor (31), completing the power generation cycle process;

[0068] Preferably, 30% of the working fluid by mass flows through the auxiliary heating branch, and 70% of the working fluid 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, and then is stored in the low-temperature storage tank 24 to complete the heat release process;

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

[0071] During peak hours, the system switches to normal operation mode, and the power generation subsystem outputs rated load power;

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

[0073] During peak hours of electricity consumption, the system switches to the energy release 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 and preheats part of the branch working fluid in the auxiliary heater 23, thereby increasing the net output of the power generation subsystem.

[0074] The system of the present invention can realize active regulation of power generation output by changing the cycle process while keeping the key parameters of the positive cycle basically unchanged.

[0075] The charging subsystem 1 absorbs excess electricity, generates low-grade thermal energy, and stores it in the heat storage subsystem 2. The low-temperature (about 200 °C) normal-pressure heat storage system has a simple structure and good technical and economic performance.

[0076] By eliminating the high-energy recompression process, the system power can be increased without adding power units or simplifying the system.

[0077] There is a significant difference in the working temperature between the reverse cycle and the forward cycle. During the charging and discharging process, low-level thermal energy can be utilized by leveraging the efficient power cycle to improve quality, which can effectively improve the round-trip efficiency of the energy storage-release process.

[0078] The system relies only on internal process reforming and deep coupling of the cycle, and does not require additional auxiliary heat sources or waste heat resources. It is universally applicable to high-temperature heat sources such as coal-based, nuclear energy, and solar thermal energy.

[0079] The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. Although the present invention has been described in detail with reference to the above embodiments, the present invention is not limited to the above specific implementation methods. Therefore, any modification or equivalent replacement of the present invention; and all technical solutions and improvements thereof that do not depart from the spirit and scope of the invention are included in the scope of the claims of the present invention.

Claims

1. An electric storage coupling system based on forward and reverse supercritical carbon dioxide cycle, characterized in that: The system comprises a charging subsystem (1), a heat storage subsystem (2) and a power generation subsystem (3); The charging subsystem (1) is used to consume the excess power of the power generation subsystem (3) and convert it into low-grade thermal energy, and comprises a compressor (11), a cooler (12), an expander (13) and a heater (14), wherein 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), and comprises 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), wherein 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 a circular manner in sequence; The power generation subsystem (3) is used for conventional cycle power generation and energy release cycle power generation, and comprises a main compressor (31), a low-temperature regenerator (32), a high-temperature regenerator (33), a main heater (34), a turbine (35), a recompressor (36), a gas cooler (37), a cooling tower (38) and a circulating 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 connected in sequence to the high-pressure side inlet of the low-temperature regenerator (32) and the high-pressure side inlet of the high-temperature regenerator (33). The auxiliary preheating branch is connected in sequence to the working fluid side inlet of the auxiliary heater (23) and the high-pressure side inlet of the high-temperature regenerator (33). The high-pressure side inlet of the high-temperature regenerator (33) is connected to the main preheating branch and the auxiliary preheating branch. The fluids are mixed at the high-pressure side inlet of the high-temperature regenerator (33). The high-pressure side outlet of the high-temperature regenerator (33) is connected in sequence to the main heater (34), the turbine (35), the low-pressure side inlet of the high-temperature regenerator (33), and the low-pressure side inlet of the low-temperature regenerator (32). The low-pressure side outlet of the low-temperature regenerator (32) is divided into a recompression branch and a main cooling branch through a second three-way valve (302). The recompression branch is connected in sequence to the inlet of the recompressor (36) and the high-pressure side inlet of the high-temperature regenerator (33). The main cooling branch is connected in sequence 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 circuit comprises a gas cooler (37), a cooling water tower (38), a circulation pump (39), and a 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 via a third three-way valve (303); the first cooling circulation branch is connected in sequence 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 are joined at the inlet of the circulation pump (39).

2. The power storage coupling system based on the forward and reverse supercritical carbon dioxide cycle according to claim 1 is characterized in that: The charging subsystem (1) and the power generation subsystem (3) use supercritical carbon dioxide as a working fluid, and the circulating heat storage medium of the heat storage subsystem (2) uses heat transfer oil.

3. A method for an electric storage coupling system based on a forward and reverse supercritical carbon dioxide cycle according to any of the above claims, 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 a recompression cycle and does not interact with the charging subsystem (1) and the heat storage subsystem (2); In the normal mode, after the working fluid at the low-pressure side outlet of the low-temperature regenerator (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 by the main compressor (31), flows through the high-pressure side inlet of the low-temperature regenerator (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 recompressor (36), and then is mixed with the working fluid in the main circuit, flows through the high-pressure side of the high-temperature regenerator (33) and the main heater (34) in sequence to absorb heat, the high-temperature and high-pressure working fluid expands and performs work through the turbine (35), and flows through the high-temperature regenerator (33) and the low-temperature regenerator (32) in sequence to release heat and cool to the high-pressure side, thereby completing the power generation (positive) cycle process; In the cooling medium circulation, the low-temperature cooling medium is pressurized 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 to the environment through the cooling water tower (38); In the energy storage mode, the charging subsystem (1) and the power generation subsystem (3) operate simultaneously, and the power generation subsystem (3) provides power to the compressor (11); In the energy storage mode, the power generation cycle of the power generation subsystem (3) is consistent with the power generation cycle described in the conventional mode. The working fluid 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 fluid flows into the expander (13) to expand and perform 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; 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), absorbs heat and rises in temperature, and then is stored in the high-temperature storage tank (21), completing the heat storage process; In the cooling medium circulation, the low-temperature cooling medium is pressurized 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 to the working medium of the charging subsystem through the cold heater (14) to reduce the temperature; In the energy release mode, 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) is operated, and the auxiliary heater (23) completes the auxiliary preheating of the branch; In the energy release mode, the working fluid at the outlet of the main compressor (31) is split, with the main part flowing through the main preheating branch and being heated by the low-temperature regenerator, and the other part flowing through the auxiliary preheating branch and absorbing heat from the high-temperature heat storage medium in the auxiliary heater (23). The two paths of working fluid then converge and flow through the high-temperature regenerator (33) and the main heater (34) in sequence to absorb heat. The high-temperature and high-pressure working fluid expands through the turbine (35) to perform work, and flows through the high-temperature regenerator (33) and the low-temperature regenerator (32) in sequence to complete the reheating process. The working fluid then flows through the gas cooler (37) to release heat to the cooling medium. The cooled working fluid is compressed and pressurized by the main compressor (31), completing the power generation cycle. 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, and then is stored in the low-temperature storage tank (24), completing the heat release process; In the cooling medium circulation, the low-temperature cooling medium is pressurized 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 to the environment through the cooling water tower (38); The peak shaving method comprises: During the peak period of electricity consumption, the system switches to the normal mode of operation, and the power generation subsystem (3) outputs rated load electricity; During the low electricity consumption period or the new energy boom period, the system switches to the energy storage operation mode, and the charging subsystem (1) consumes part of the electricity of the power generation subsystem (3), generates low-grade heat energy, and stores it in the high-temperature storage tank (21), thereby reducing the overall net output of the system; During peak electricity consumption, the system switches to an energy release operation mode, the recompressor (36) of the power generation subsystem (3) is shut down, and the high-temperature heat storage medium releases heat and preheats part of the branch circuit working fluid in the auxiliary heater (23), thereby increasing the net output of the power generation subsystem.

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