Coal-fired power generation and energy storage integrated system and working method thereof

Abstract

The invention discloses a coal-fired power generation and energy storage integrated system and a working method thereof, and relates to the technical field of coal-fired power generation unit transformation, and the coal-fired power generation and energy storage integrated system comprises a coal-fired power generation unit, a high-temperature heat storage module and a compressed working medium energy storage module; the compression working medium energy storage module comprises a first heat storage module and a first working medium loop, first working medium fluid is introduced into the first working medium loop, and the first working medium loop comprises a first expansion energy release line and a first compression energy storage line; the first expansion energy release line comprises a plurality of pairs of first heaters and first expansion machines, the high-temperature heat storage module heats a first working medium through the first heaters, and the heated first working medium pushes the first expansion machines to generate electricity through expansion; and the compressed first working medium transfers compression heat to the first heat storage module for storage through the first heat exchanger. And the effects of deep peak regulation, peak power generation or rapid load climbing and the like of the power-assisted coal-fired power generation unit are achieved.

Description

Technical Field

[0001] This invention relates to the field of coal-fired power generation unit retrofitting technology, and in particular to an integrated coal-fired power generation and energy storage system and its operating method. Background Technology

[0002] Currently, the application and promotion of energy storage methods such as thermal energy storage, flywheels, and batteries coupled with coal-fired power generating units are becoming increasingly widespread and have yielded significant benefits, proving that the integrated innovation of coal power and energy storage is a feasible implementation path. With the increasing technical requirements for coal-fired power generating units, including deep peak shaving, load change rate, start-up and shutdown, coal consumption for power supply, safety and reliability, low carbon emissions, and intelligentization, more innovative solutions for coal-power coupled energy storage need to be developed and applied. Due to the limitations of the operating conditions of coal-fired power generating units, the amount of heat energy drawn from the unit to the thermal storage is relatively limited. Therefore, the peak-shaving depth of the unit is often expanded by further drawing on the power output of the generator to electrically heat the high-temperature thermal storage. Ultimately, the unit's power output can be as low as 20% of the rated load or even lower. However, the energy storage round-trip efficiency of the system is low (50% to 60%), resulting in excessively high coal consumption rate and little effect on improving the unit's load ramp-up rate and peak power output. In recent years, the technology of compressed working fluid energy storage coupled with coal-fired power generation units has also been developed. In the energy storage mode, it draws on the electrical energy generated by the unit, but at the same time, it sends the compressed heat energy back to the unit. This will greatly reduce the effect of energy storage in improving the peak shaving depth of the unit. In the energy release mode, it absorbs heat from the unit to heat the working fluid while generating electricity, which will greatly reduce the effect of energy storage in improving the peak power generation of the unit. It can be seen that in the existing technical solution of compressed working fluid energy storage coupled with coal-fired power generation units, the heat and electricity flow in opposite directions, and the heat and power synergy needs to be improved. Summary of the Invention

[0003] The purpose of this invention is to provide an integrated coal-fired power generation and energy storage system and its operating method. Based on the energy attributes of coal-fired power generating units, through independently configured high-temperature thermal storage modules and compressed working fluid energy storage modules, during deep peak shaving of coal-fired power generating units, a portion of the thermal energy and electrical energy are converted to the high-temperature thermal storage modules and compressed working fluid energy storage modules respectively, so as to reduce the amount of electricity supplied to the grid or quickly reduce the load, thereby assisting the coal-fired power generating units in deep peak shaving and alleviating the increase in coal consumption for power supply. When the coal-fired power generating units are generating electricity at peak times, through the energy release process of the compressed working fluid energy storage module, the thermal energy in the high-temperature thermal storage module is carried together and efficiently converted into electrical energy to supply electricity to the grid, thereby assisting the coal-fired power generating units in generating electricity at peak times or rapidly ramping up the load.

[0004] The above technical objectives of the present invention are achieved through the following technical solutions: A coal-fired power generation and energy storage integrated system includes a coal-fired generator set, a high-temperature thermal energy storage module, and a compressed working fluid energy storage module. The coal-fired generator set supplies power to the grid and stores thermal energy in the high-temperature thermal energy storage module. The compressed working fluid energy storage module includes a first thermal energy storage module and a first working fluid circuit. A first working fluid is passed through the first working fluid circuit, which includes a first expansion energy release line and a first compression energy storage line. The first expansion energy release circuit includes several pairs of first heaters and first expanders. The high-temperature thermal storage module heats the first working fluid through the first heaters. The heated first working fluid drives the first expander to expand and generate electricity. The first compression energy storage circuit includes several pairs of first compressors and first heat exchangers. The first compressor compresses the first working fluid. The compressed first working fluid transfers the heat of compression to the first thermal storage module for storage through the first heat exchanger.

[0005] Furthermore, the compressed working fluid energy storage module also includes a gas storage tank, which is equipped with a flexible diaphragm or a free piston, dividing the gas storage tank into a first deformable airtight space and a second deformable airtight space that are not interconnected, storing the first working fluid and the second working fluid in gaseous state respectively. The first deformable airtight space is connected to the first working fluid circuit, and the second deformable airtight space is connected to the second working fluid circuit. The second working fluid circuit performs energy storage and / or energy release.

[0006] Furthermore, the compressed working fluid energy storage module includes a liquid storage tank that stores a second working fluid. The liquid storage tank is connected to a second working fluid circuit, through which a second working fluid is circulated. The second working fluid circuit includes a second expansion energy release line and a second compression energy storage line. The second expansion energy release circuit includes several pairs of second heaters and a second expander. The second heater heats the second working fluid through a high-temperature thermal storage module. The heated second working fluid drives the second expander to expand and generate electricity. The second compression energy storage circuit includes a second compressor and a condenser. The second compressor compresses the second working fluid. The compressed second working fluid is liquefied after being cooled by the condenser.

[0007] Furthermore, the second expansion energy release circuit also includes a second regenerator and a preheater. The exhaust gas from the second expander transfers its waste heat to the second working fluid before it enters the second heater through the second regenerator. The preheater preheats the second working fluid from the storage tank by combining the compression heat stored in the first heat storage module and the waste heat of the second working fluid discharged from the second regenerator.

[0008] Furthermore, the outlet of the liquid storage tank is also connected to a booster pump, which increases or compresses the pressure of the second working fluid output from the liquid storage tank to a supercritical state.

[0009] Furthermore, the high-temperature thermal storage module includes a cold salt tank, a hot salt tank, and a molten salt heat exchanger. The molten salt heat exchanger includes a molten salt flow channel and a hot flow channel. The two ends of the molten salt flow channel are connected to the cold salt tank and the hot salt tank, respectively. The hot flow channel is connected to the circuit of high-temperature steam or high-temperature flue gas from the coal-fired power generation unit.

[0010] Furthermore, it also includes cooling towers, whose cooling water supplies the coal-fired power generation unit, condenser, and second compressor.

[0011] This invention also discloses a method for operating a coal-fired power generation and energy storage integrated system, comprising the following steps: During energy storage, the high-temperature thermal storage module and / or the compressed working fluid energy storage module are activated. Among them, the coal-fired power generation unit provides heat energy to the high-temperature thermal storage module and stores it; the compressed working fluid energy storage module compresses the first working fluid through the first compressor, and the compressed first working fluid transfers the compression heat to the first thermal storage module for storage through the first heat exchanger, and finally stores it in the first deformable airtight space of the gas storage tank. Simultaneously, the second working fluid is controlled to be output from the second deformable airtight space of the gas storage tank, and then stored through the second working fluid loop. When releasing energy, the high-temperature thermal storage module and / or the compressed working fluid energy storage module are activated. The high-temperature thermal storage module heats the feedwater from the coal-fired generator set, turning the water into high-temperature steam that returns to the steam turbine water system in the coal-fired generator set. The first deformable airtight space of the compressed working fluid energy storage module releases the first working fluid. The high-temperature thermal storage module heats the first working fluid through the first heater. The heated first working fluid drives the first expander to expand and generate electricity. Simultaneously, the second working fluid circuit is controlled to release energy. After energy release, the second working fluid returns to the second deformable airtight space of the gas storage tank.

[0012] Furthermore, if the compressed working fluid energy storage module has exhausted its capacity, but the high-temperature thermal energy storage module still has remaining capacity, the first compressor is started to directly supply gas to the first expander to continue generating electricity, causing the high-temperature thermal energy storage module to release its stored heat until its capacity is emptied.

[0013] Furthermore, if the high-temperature thermal energy storage module has exhausted its capacity, but the compressed working fluid energy storage module still has remaining capacity, the coal-fired power generation unit will draw heat energy to input into the high-temperature thermal energy storage module, continuously supplying heat energy to the first heater, so that the compressed working fluid energy storage module can release energy to generate electricity until its capacity is exhausted.

[0014] In summary, the present invention has the following beneficial effects: During the deep peak shaving phase, coal-fired power generating units can flexibly utilize molten salt thermal storage and compressed working fluid energy storage to reduce load. During the peak power generation phase, they can flexibly utilize molten salt thermal storage and compressed working fluid energy storage to release energy and increase load, thereby expanding the regulation capacity range of coal-fired power generating units and increasing the load change rate, thus mitigating the deterioration of coal consumption indicators caused by deep peak shaving. The operation of molten salt thermal storage and compressed working fluid energy storage is decoupled from the deep peak shaving operation of coal-fired power generation and will not have a negative impact on the safety and reliability of coal-fired power generating units. The present invention features strong energy flow coordination. During deep peak shaving, the coal-fired power generation unit unidirectionally supplies heat and electricity to the energy storage device. During peak power generation, the coal-fired power generation unit does not supply energy to the energy storage device. The energy storage device synergistically converts heat and working fluid pressure energy into electrical energy to directly supply power to the grid. The compressed working fluid energy storage module utilizes the synergistic effect of the first and second working fluids to achieve rapid energy storage and release response. It combines expansion power generation with molten salt heat release and utilizes the supercritical second working fluid to efficiently recover and utilize the stored compression heat to avoid waste of residual heat, thereby significantly improving energy conversion efficiency and energy storage round-trip efficiency. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the process flow of the coal-fired power generation and energy storage integrated system and its working method of the present invention; Figure 2 This is a deep peak-shaving energy flow diagram of the coal-fired power generation and energy storage integrated system and its working method of the present invention; Figure 3 This is a peak power generation energy flow diagram of the coal-fired power generation and energy storage integrated system and its working method of the present invention. Detailed Implementation

[0016] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. These embodiments do not constitute a limitation of the present invention. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this application.

[0017] A coal-fired power generation and energy storage integrated system, such as Figure 1 As shown, it includes coal-fired power generating units, high-temperature thermal energy storage modules, and compressed working fluid energy storage modules. Especially during deep peak shaving in periods of high renewable energy generation or low load, coal-fired power generating units supply power to the grid, store thermal energy in high-temperature thermal energy storage modules, and store electrical energy in compressed working fluid energy storage modules. The coal-fired power generating unit consists of a boiler, steam turbine, generator, and other main components, as well as other systems and auxiliary equipment. Based on the Rankine thermodynamic cycle principle of steam as the working fluid, it involves subcritical, supercritical, and ultra-supercritical parameter levels. As a supporting and regulating power source in the power system, it is used to coordinate with renewable energy generation, which is intermittent, random, and fluctuating. During periods of high renewable energy generation or low load, the coal-fired power generating unit stores thermal energy in high-temperature thermal storage modules and electrical energy in compressed working fluid energy storage modules to minimize the power supplied by the coal-fired power generating unit to the grid, so that renewable energy can give priority to powering the grid. During periods of low renewable energy generation or high load, the coal-fired power generating unit works in conjunction with high-temperature thermal storage modules and compressed working fluid energy storage modules to generate peak power and ensure grid security.

[0018] like Figure 1 As shown, the high-temperature thermal storage module includes a cold salt tank, a hot salt tank, and a molten salt heat exchanger. The thermal storage power can be selected as 10% to 20% of the rated thermal power of the coal-fired generator set. The heat transfer and thermal storage medium used is molten salt, and the type of molten salt can be selected as binary salt, ternary salt, etc., according to the working temperature range. The molten salt heat exchanger includes a molten salt flow channel and a hot flow channel. The two ends of the molten salt flow channel are connected to the cold salt tank and the hot salt tank, respectively, and the hot flow channel is connected to the high-temperature steam or high-temperature flue gas circuit of the coal-fired generator set. During heat storage, the molten salt heat exchanger transfers the heat energy from the high-temperature steam or flue gas of the coal-fired power plant to the lower-temperature molten salt from the cold salt tank. The molten salt, after absorbing heat and heating up, enters the hot salt tank for storage. During heat release, the molten salt output from the hot salt tank releases heat to the compressed working fluid energy storage module and / or the coal-fired power plant, cools down, and then returns to the cold salt tank for storage. The operating temperature (T) of the hot salt tank of the high-temperature heat storage module is selected to be as high as possible, preferably T>400℃, so the higher temperature heat source of the coal-fired power plant is preferred. In some embodiments, the high-temperature heat storage module can be divided into multiple groups for heat storage according to different operating temperatures.

[0019] like Figure 1 As shown, the compressed working fluid energy storage module includes sub-modules such as a gas storage tank, a liquid storage tank, a first thermal storage module, a first working fluid circuit, and a second working fluid circuit. The energy storage capacity can be selected as 10% to 20% of the rated output of the coal-fired power generation unit. The gas storage facility includes a pressurized airtight space, within which a flexible diaphragm or free piston is built. The flexible diaphragm or free piston divides the interior of the pressurized airtight space into a first deformable airtight space and a second deformable airtight space, which are not interconnected. These spaces store a first gaseous working fluid and a second gaseous working fluid, respectively. In this embodiment, the first working fluid is air, and the second working fluid is carbon dioxide. The flexible diaphragm is freely deformable, or the free piston is freely movable, to change the shape and volume of the first and second deformable airtight spaces, ensuring that the pressure in both spaces remains equal at all times. When the first deformable airtight space is filled with the first working fluid and its volume expands, the second deformable airtight space correspondingly outputs the second working fluid and its volume shrinks; when the first deformable airtight space outputs the first working fluid and its volume shrinks, the second deformable airtight space correspondingly inputs the first working fluid and its volume expands, so that the two working fluids share the pressurized airtight space, the filling and discharging process can be controlled to achieve complete filling and discharging, and the pressure of the pressurized airtight space can be kept constant. The pressurized airtight space can be constructed using structures such as ground containers, underground caves, or deep-water airbags, and can be arranged in multiple interconnected groups. The working pressure (P1) of the gas storage facility remains constant, with the P1 value selected within the range of [2.5MPa, 6.5MPa]. A P1 value of 5MPa or higher is preferred to reduce the volume or floor space of the gas storage facility. The working temperature of the gas storage facility is ambient temperature, and it is equipped with a temperature control device to prevent the working fluid from undergoing a phase change that could disrupt the constant pressure condition. It is also equipped with an overpressure protection device to control the pressure and prevent structural failure of the pressurized airtight space.

[0020] like Figure 1 As shown, the liquid storage tank includes a rigid pressure-bearing space for storing a liquid second working fluid; the rigid pressure-bearing space can be a container or a cave structure, and can be divided into multiple interconnected groups; the working pressure (P2) of the liquid storage tank is always kept constant, and the selection range of the P2 value is [7.5MPa, 8.5MPa]; the working temperature of the liquid storage tank is room temperature, and it is equipped with temperature control measures to adjust the ratio of gas phase and liquid phase volume to maintain constant pressure conditions, and is equipped with an overpressure protection device to control the pressure to prevent structural failure of the rigid pressure-bearing space; A booster pump is configured at the outlet of the liquid storage tank. The inlet of the booster pump is connected to the outlet of the rigid pressure space. It is used to further compress the second working fluid output from the liquid storage tank. In this embodiment, the booster pump increases or compresses the pressure of the second working fluid output from the liquid storage tank to a supercritical state. The range of the booster pump outlet pressure (P3) value is [10MPa, 30MPa]. The compression stages of the booster pump can be selected with or without intermediate cooling.

[0021] like Figure 1 As shown, the first deformable airtight space is connected to the first working fluid loop and is supplied with the first working fluid; the second deformable airtight space is connected to the second working fluid loop and is supplied with the second working fluid; the system stores and / or releases energy through the first working fluid loop and the second working fluid loop. The first working fluid circuit includes a first expansion energy release line and a first compression energy storage line; wherein, the first compression energy storage line is used for compression energy storage of the first working fluid in the energy storage condition, and the first expansion energy release line is used for expansion power generation of the first working fluid in the energy release condition.

[0022] like Figure 1As shown, the first expansion energy release circuit includes a first regenerator, several first heaters, a first expander, and their connecting pipelines. The high-temperature thermal storage module heats the first working fluid through the first heaters, and the heated first working fluid drives the first expander to expand and generate electricity. Specifically, the cold-side inlet of the first regenerator is connected to the first deformable airtight space of the gas storage tank through a valve, and the outlet is connected to the first heater (the first working fluid is supplied to the first heater through the first deformable airtight space). The outlet of the first working fluid of the first heater is connected to the inlet of the first expander. The first heater and the first expander form 2 to 4 pairs and are connected in series. The expansion ratio of each section of the first expander is set so that its outlet temperature is close to the minimum working temperature of the molten salt. The first heater uses the heat energy from the high-temperature thermal storage module to heat the first working fluid entering the first expander. The first working fluid from the first regenerator gradually expands and inputs the exhaust gas into the hot side of the first regenerator. The exhaust gas of the first expander transfers the waste heat to the first working fluid before entering the first heater through the first regenerator. The molten salt inlet of the first heater is connected to the outlet of the hot salt tank, and the molten salt outlet of the first heater is connected to the inlet of the cold salt tank. The first compression energy storage line includes several first compressors, first heat exchangers and their connecting pipelines. The first compressors compress the first working fluid, and the compressed first working fluid transfers the heat of compression to the first heat storage module for storage through the first heat exchanger. Specifically, the outlet of the first compressor is connected to the inlet of the first working fluid of the first heat exchanger. The two form 3 to 5 pairs and are connected in series, so that the pressure of the first working fluid is gradually increased to the specified pressure, and then finally transported to the first deformable airtight space of the gas storage tank through valves, etc. The pressure ratio of each section of the first compressor is set so that the outlet temperature is similar, and the heat of compression is recovered through the first heat exchanger. In this embodiment, the first heat storage module is a water heat storage device used to store the heat of compression, so that the first working fluid eventually returns to the first deformable airtight space after becoming room temperature and high pressure. The working pressure can be set according to the working temperature to ensure that the water is in a liquid state. It includes a cold water tank and a hot water tank. The outlet of the cold water tank is connected to the water inlet of the first heat exchanger, and the water outlet of the first heat exchanger is connected to the inlet of the hot water tank.

[0023] like Figure 1 As shown, the second working fluid circuit includes a second expansion energy release line and a second compression energy storage line; the second compression energy storage line is used for compression energy storage of the second working fluid in the energy storage condition, and the second expansion energy release line is used for expansion power generation of the second working fluid in the energy release condition. The second expansion energy release circuit includes a preheater, a second regenerator, a second heater, a second expander and their connecting pipelines. The second heater heats the second working fluid in the storage tank through a high-temperature thermal storage module. The heated second working fluid drives the second expander to expand and generate electricity, and then returns to the second deformable airtight space. Specifically, the booster pump outlet is connected to the cold-side second working fluid inlet of the preheater, the cold-side second working fluid outlet of the preheater is connected to the cold-side second working fluid inlet of the second regenerator, the cold-side second working fluid outlet of the second regenerator is connected to the second working fluid inlet of the second heater (the second working fluid supplied from the storage tank to the second heater is introduced), the second working fluid outlet of the second heater is connected to the inlet of the second expander, and the outlet of the second expander is connected to the hot-side second working fluid inlet of the second regenerator (the exhaust gas of the second working fluid finally discharged from the second expander is introduced, and the exhaust gas of the second expander transfers residual heat to the second working fluid before entering the second heater through the second regenerator). The hot-side second working fluid outlet of the second regenerator is connected to the hot-side second working fluid inlet of the preheater. The hot-side second working fluid outlet of the preheater is connected to the inlet of the second deformable airtight space through a valve. In this embodiment, the preheater is a three-flow heat exchanger type. In addition to a cold-side inlet and outlet connected to the booster pump and the second regenerator respectively, a hot-side inlet and outlet connected to the second regenerator and the second deformable airtight space respectively, there is also a hot-side inlet and outlet connected to the hot water tank and the cold water tank respectively. The inlet end of the hot water tank is located at the end of the preheater away from its cold-side second working fluid inlet, so that the flow direction of the hot water in the preheater is in the opposite direction to the second working fluid coming out of the liquid storage tank. The waste heat of the second working fluid discharged from the second regenerator and the hot water from the hot water tank (the compression heat stored in the first heat storage module) are used to preheat the second working fluid from the liquid storage tank. The second compression energy storage line includes a second compressor, a condenser and their connecting pipelines. The second compressor controls and compresses the second working fluid in the second deformable airtight space through a valve. The compressed second working fluid is cooled by the condenser and then stored in the liquid storage tank. Specifically, the compression stages of the second compressor can be either intercooled or not. The inlet of the second compressor is connected to the outlet of the second deformable airtight space, the outlet of the second compressor is connected to the inlet of the second working fluid of the condenser, and the outlet of the second working fluid of the condenser is connected to the inlet of the rigid pressure space of the liquid storage tank through a valve.

[0024] The integrated system in this embodiment also includes a cooling tower. The cooling water from the cooling tower supplies cooling water to the coal-fired power generator set, the condenser, and the second compressor. This allows the cooling tower to serve as a cold source for the coal-fired power generator set and to share its use with the compressed working fluid energy storage module. When the coal-fired power generator set is deeply shaving off peak loads and calling upon the compressed working fluid energy storage module, it provides cooling water to the second compressor and the condenser. At this time, the coal-fired power generator set is operating under low load conditions. If the cooling tower has sufficient residual cooling capacity, it can also be used to provide cooling water to the booster pump when the coal-fired power generator set is generating electricity at its peak.

[0025] This embodiment also discloses a working method for an integrated coal-fired power generation and energy storage system, including the following: I. A method for deep peak shaving of coal-fired power generating units by combining molten salt thermal storage and compressed working fluid energy storage like Figure 1 and Figure 2 As shown, after receiving the deep peak shaving command from the power grid, the coal-fired power generating unit first controls its own load regulation function to reduce output. When the load reduction rate of the coal-fired power generating unit is insufficient, or the coal consumption rate rises sharply as the load decreases, or it drops to the safe operating limit, the molten salt thermal storage and / or compressed working fluid energy storage are activated, and its operating status is controlled according to the change in energy storage power. On the one hand, the coal-fired power generation unit provides heat energy to the high-temperature thermal storage module and stores it: part of the heat energy generated by the boiler is quickly switched to the molten salt heat exchanger in the form of high-temperature steam or high-temperature flue gas, and the flow rate of molten salt output from the cold salt tank is controlled to match the heat exchange capacity of the molten salt heat exchanger. After the molten salt is heated to the specified temperature, it is input into the hot salt tank for storage. On the other hand, part of the electrical energy generated by the turbine-driven generator is supplied to the compressed working fluid energy storage module for energy storage and energy storage. The first compressor is controlled to compress the first working fluid, so that the first compressor and the second compressor can start quickly and their operating status is controlled. The first working fluid is compressed by the first compressor. The compressed first working fluid exchanges heat with the water heat storage device through the first heat exchanger. The output water flow of the cold water tank of the water heat storage device is controlled so that the heat of compression of the first working fluid is absorbed by the water and stored in the hot water tank. Finally, the first working fluid in the normal temperature high pressure gaseous state is stored in the first deformable airtight space of the gas storage tank. Simultaneously, the flow rate of the second working fluid output from the second deformable airtight space of the gas storage tank is controlled, and the second compressor is controlled to compress the second working fluid. Then, the fluid is cooled and liquefied by the condenser (transformed into a normal temperature high-pressure liquid state). The cooling of the compression and condensation process is achieved by controlling the cooling tower to provide the required amount of cooling water to reduce the compression work of the second compressor and the energy consumption of the condenser. Finally, the liquid second working fluid is stored in the rigid pressure space of the liquid storage tank. The molten salt thermal storage and compressed working fluid energy storage are controlled to operate independently and continuously or intermittently. Depending on the peak shaving depth, both or one of them can be activated simultaneously to reduce the power supplied to the grid by coal-fired power generating units, thereby completing the grid's deep peak shaving task.

[0026] If the high-temperature thermal storage module or the compressed working fluid energy storage module is not fully charged to its rated energy storage capacity, it can be controlled to continue to replenish energy storage after completing the deep peak shaving task, thereby preparing sufficient energy release capacity for subsequent peak power generation tasks.

[0027] II. A method for coordinating molten salt thermal storage and compressed working fluid energy storage with peak power generation of coal-fired power plants. like Figure 1 and Figure 3 As shown, after receiving the peak power generation command from the power grid, the coal-fired power generating unit first controls its own load regulation function to increase its output. When the load ramp-up rate of the coal-fired power generating unit is insufficient, or when it reaches the safe operating limit, it starts molten salt thermal storage and / or compressed working fluid energy storage, and controls its operating status according to the changes in energy storage power. On the one hand, the hot salt tank in the high-temperature thermal storage module rapidly outputs molten salt and controls the flow rate of the molten salt. The molten salt heat exchanger heats the feedwater from the coal-fired generator set, turning the water into high-temperature steam and returning it to the steam turbine water system of the coal-fired generator set to increase the output of the coal-fired generator set. After the heat is released, the molten salt is returned to the cold salt tank. On the other hand, the first deformable airtight space of the gas storage tank rapidly releases the first working fluid and is heated by the first regenerator. Correspondingly, the rigid pressure space of the liquid storage tank is controlled to rapidly release the second working fluid. At the same time, the high-temperature thermal storage module provides heat to the compressed working fluid energy storage module. The hot salt tank rapidly outputs molten salt and controls the flow rate of the molten salt. The first working fluid entering the first expander and the second working fluid entering the second expander are heated by the first heater and the second heater, respectively. After the molten salt has finished releasing heat, it returns to the cold salt tank. The high-temperature and high-pressure first working fluid drives the first expander to expand and generate electricity and reduce the pressure to atmospheric pressure. The exhaust gas is discharged and the waste heat is recovered by the first regenerator and transferred to the first working fluid with normal temperature and high pressure output from the first deformable airtight space (since the first working fluid is air, at the first end of the first compression energy storage line, the first compressor directly compresses the outside air, while at the end of the first expansion energy release line, the first working fluid is directly discharged after being reheated by the last first regenerator). Simultaneously, the second working fluid loop releases energy. The second working fluid is output from the liquid storage tank and vaporized by the preheater and heated by the second regenerator. The high-temperature thermal storage module heats the second working fluid through the second heater. After heating, the high-temperature and high-pressure second working fluid drives the second expander to expand and generate electricity, and reduces the pressure to the working pressure of the gas storage tank. The exhaust gas is discharged and passes through the second regenerator and preheater to recover waste heat and transfer it to the supercritical second working fluid delivered by the booster pump. The output water flow of the hot water tank is controlled. The heat carried by the water is fully recovered and utilized by the preheater. After the heat is released, the water returns to the cold water tank. The exhaust gas of the second working fluid after the heat is released is finally input into the second deformable airtight space of the gas storage tank. The high-temperature thermal storage module and the compressed working fluid energy storage module are coupled and operated in coordination with the coal-fired power generation unit to increase the power supplied to the grid and complete the peak power generation task of the grid.

[0028] If the compressed working fluid energy storage module has exhausted its capacity while the high-temperature thermal storage module still has remaining capacity, the first compressor and the second compressor can be started to directly supply gas to the first expander and the second expander to continue generating electricity, so that the high-temperature thermal storage module can be released to its full capacity. If the high-temperature thermal energy storage module has exhausted its capacity while the compressed working fluid energy storage module still has remaining capacity, the coal-fired power generation unit can draw heat energy into the high-temperature thermal energy storage module to continuously supply heat energy to the first and second heaters, enabling the compressed working fluid energy storage module to release energy and generate electricity until its capacity is exhausted.

[0029] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art can make various modifications or equivalent substitutions to the present invention within the scope of its essence and protection. Such modifications or equivalent substitutions should also be considered to fall within the protection scope of the present invention.

Claims

1. A coal-fired power generation and energy storage integrated system, characterized in that: It includes a coal-fired power generation unit, a high-temperature thermal energy storage module, and a compressed working fluid energy storage module. The coal-fired power generation unit supplies power to the grid and stores thermal energy in the high-temperature thermal energy storage module. The compressed working fluid energy storage module includes a first thermal energy storage module and a first working fluid circuit. The first working fluid circuit is filled with a first working fluid and includes a first expansion energy release line and a first compression energy storage line. The first expansion energy release circuit includes several pairs of first heaters and first expanders. The high-temperature thermal storage module heats the first working fluid through the first heaters. The heated first working fluid drives the first expander to expand and generate electricity. The first compression energy storage circuit includes several pairs of first compressors and first heat exchangers. The first compressor compresses the first working fluid. The compressed first working fluid transfers the heat of compression to the first thermal storage module for storage through the first heat exchanger.

2. The coal-fired power generation and energy storage integrated system according to claim 1, characterized in that: The compressed working fluid energy storage module also includes a gas storage tank, which is equipped with a flexible diaphragm or a free piston, dividing the gas storage tank into a first deformable airtight space and a second deformable airtight space that are not interconnected. The first and second working fluids are stored in gaseous state, respectively. The first deformable airtight space is connected to the first working fluid circuit, and the second deformable airtight space is connected to the second working fluid circuit. The second working fluid circuit performs energy storage and / or energy release.

3. The coal-fired power generation and energy storage integrated system according to claim 2, characterized in that: The compressed working fluid energy storage module includes a liquid storage tank, which stores a second working fluid. The liquid storage tank is connected to a second working fluid circuit, and a second working fluid fluid flows through the second working fluid circuit. The second working fluid circuit includes a second expansion energy release line and a second compression energy storage line. The second expansion energy release circuit includes several pairs of second heaters and a second expander. The second heater heats the second working fluid through a high-temperature thermal storage module. The heated second working fluid drives the second expander to expand and generate electricity. The second compression energy storage circuit includes a second compressor and a condenser. The second compressor compresses the second working fluid. The compressed second working fluid is liquefied after being cooled by the condenser.

4. The coal-fired power generation and energy storage integrated system according to claim 3, characterized in that: The second expansion energy release circuit also includes a second regenerator and a preheater. The exhaust gas from the second expander transfers its waste heat to the second working fluid before it enters the second heater through the second regenerator. The preheater preheats the second working fluid from the storage tank by combining the compression heat stored in the first heat storage module and the waste heat of the second working fluid discharged from the second regenerator.

5. The coal-fired power generation and energy storage integrated system according to claim 3 or 4, characterized in that: The outlet of the liquid storage tank is also connected to a booster pump, which increases or compresses the pressure of the second working fluid output from the liquid storage tank to a supercritical state.

6. The coal-fired power generation and energy storage integrated system according to claim 1, characterized in that: The high-temperature thermal storage module includes a cold salt tank, a hot salt tank, and a molten salt heat exchanger. The molten salt heat exchanger includes a molten salt flow channel and a hot flow channel. The two ends of the molten salt flow channel are connected to the cold salt tank and the hot salt tank, respectively. The hot flow channel is connected to the circuit of high-temperature steam or high-temperature flue gas of the coal-fired power generation unit.

7. The coal-fired power generation and energy storage integrated system according to claim 3, characterized in that: It also includes cooling towers, whose cooling water supplies the coal-fired power generation unit, condenser, and second compressor.

8. A method for operating the coal-fired power generation and energy storage integrated system as described in claim 2, characterized in that: Includes the following steps, During energy storage, the high-temperature thermal storage module and / or the compressed working fluid energy storage module are activated. Among them, the coal-fired power generation unit provides heat energy to the high-temperature thermal storage module and stores it; the compressed working fluid energy storage module compresses the first working fluid through the first compressor, and the compressed first working fluid transfers the compression heat to the first thermal storage module for storage through the first heat exchanger, and finally stores it in the first deformable airtight space of the gas storage tank. Simultaneously, the second working fluid is controlled to be output from the second deformable airtight space of the gas storage tank, and then stored through the second working fluid loop. When releasing energy, the high-temperature thermal storage module and / or the compressed working fluid energy storage module are activated. The high-temperature thermal storage module heats the feedwater from the coal-fired generator set, turning the water into high-temperature steam that returns to the steam turbine water system in the coal-fired generator set. The first deformable airtight space of the compressed working fluid energy storage module releases the first working fluid. The high-temperature thermal storage module heats the first working fluid through the first heater. The heated first working fluid drives the first expander to expand and generate electricity. Simultaneously, the second working fluid circuit is controlled to release energy. After energy release, the second working fluid returns to the second deformable airtight space of the gas storage tank.

9. The operating method of the coal-fired power generation and energy storage integrated system according to claim 8, characterized in that: If the compressed working fluid energy storage module has exhausted its capacity, but the high-temperature thermal storage module still has remaining capacity, the first compressor is started to directly supply gas to the first expander to continue generating electricity, causing the high-temperature thermal storage module to release its stored heat until its capacity is emptied.

10. The operating method of the coal-fired power generation and energy storage integrated system according to claim 8 or 9, characterized in that: If the high-temperature thermal energy storage module has exhausted its capacity, but the compressed working fluid energy storage module still has remaining capacity, the coal-fired generator set will draw heat energy to input into the high-temperature thermal energy storage module, continuously supplying heat energy to the first heater, so that the compressed working fluid energy storage module can release energy to generate electricity until its capacity is exhausted.

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