A near-constant pressure pressurized hot water storage system and its operation method

Abstract

This invention discloses a near-constant-pressure pressurized hot water thermal storage system, relating to the technical field of thermal storage systems in compressed air energy storage power stations. It includes a pressurized hot water thermal storage system comprising a high-temperature water tank and a low-temperature water tank; both the high-temperature and low-temperature water tanks contain pressure-stabilizing gas and are connected by a connecting pipe; it also includes a pressure stabilization system, comprising a buffer tank, a high-pressure gas storage tank, and a pressure-stabilizing gas pressurization system; the buffer tank and the high-pressure gas storage tank are connected to the connecting pipe. Compared to existing high-pressure high-temperature hot water thermal storage systems, this invention effectively reduces the gas-side pressure fluctuation range of the high and low-temperature water tanks, effectively alleviates stress fatigue in the tanks, improves the service life and safety of the tanks, reduces design difficulty and the measures required, and lowers tank costs. This invention also relates to an operation method for this near-constant-pressure pressurized hot water thermal storage system.

Description

Technical Field

[0001] This invention relates to the technical field of thermal storage systems for compressed air energy storage power plants, and more specifically, to a near-constant-pressure pressurized hot water thermal storage system. The invention also relates to an operation method for this near-constant-pressure pressurized hot water thermal storage system. Background Technology

[0002] Compressed air energy storage systems are currently recognized as a large-capacity, ultra-long-duration energy storage technology comparable to pumped hydro storage. They can provide auxiliary services to the power grid such as peak shaving, frequency regulation, phase regulation, black start, and rotational inertia, and have attracted widespread attention from scholars at home and abroad. At present, several large-capacity compressed air energy storage projects have been completed or are under construction in China.

[0003] Compressed air energy storage systems include compressed air energy storage systems, expansion power generation systems, thermal storage systems, heat exchange systems, and gas storage systems. The main technical indicators of compressed air energy storage power plants include cost and electro-electric conversion efficiency. According to relevant research, under the same boundary conditions, the electro-electric conversion efficiency gradually increases with increasing thermal storage temperature. However, as the thermal storage temperature increases, a significant issue arises: the applicability and economic viability of the thermal storage medium. Currently, the mainstream system solutions for increasing thermal storage temperature use heat transfer oil or molten salt as the thermal storage medium. However, heat transfer oil has problems such as high cost, toxicity, and safety risks. Molten salt has a significantly lower cost compared to heat transfer oil, but its proportion of the overall power plant investment is still considerable. Furthermore, liquid molten salt has a high freezing point, posing a condensation risk during power plant start-up and shutdown, as well as during shutdowns, which has a significant impact on the safe and stable operation of the power plant. Therefore, it can be seen that the choice of thermal storage system in a compressed air energy storage power plant directly determines the power plant's economy and efficiency.

[0004] To address the aforementioned issues, the applicant has filed patents including "Compressed Air Energy Storage System Using High-Pressure High-Temperature Hot Water for Thermal Storage" (application number: 202123240965.2), "A Pressure Self-Balancing High-Temperature Hot Water Thermal Storage System and Its Operation Method" (application number: 202111476481.1), and "Compressed Air Energy Storage System Using High-Pressure High-Temperature Hot Water for Thermal Storage and Its Operation Method" (application number: 202111577916.X). These patents propose a pressure self-balancing thermal storage system that uses pressurized hot water as the thermal storage medium. By cleverly utilizing pressurized water as the thermal storage medium, the system can effectively increase the thermal storage temperature, thereby improving thermal efficiency. The system boasts high electro-to-electric conversion efficiency, while avoiding the problems of high investment, toxicity and safety risks, and easy condensation associated with using heat transfer oil and molten salt as heat storage media. The heat storage system and solution proposed in the above patent have been demonstrated in several large-capacity compressed air energy storage power stations under construction or planned in China. Among them, a 300MW compressed air energy storage power station demonstration project, which was constructed by the applicant as an EPC general contractor, was first connected to the grid and generated electricity on April 9, 2024, and passed half-capacity trial operation on July 28, 2024, fully verifying the feasibility and effectiveness of using a pressurized hot water heat storage system in compressed air energy storage power stations.

[0005] To ensure the hot water remains liquid throughout operation and prevent vaporization, this pressurized hot water storage system utilizes pressurized gas to maintain the tank pressure at a level no lower than the saturation pressure corresponding to the storage temperature (taking the 180℃ storage temperature example from the aforementioned patent as an example, the corresponding saturation pressure is 1.0 MPa). Simultaneously, to cope with pressure fluctuations caused by changes in the liquid level within the tank, both the high-temperature and low-temperature tanks are designed to withstand pressures greater than the saturation pressure corresponding to the storage temperature (taking the 180℃ storage temperature example from the aforementioned patent as an example, the maximum tank pressure is no less than 1.5 MPa). As can be seen from the above, the system's tank design pressure is greater than the saturation pressure corresponding to the storage temperature. Increased design pressure of storage tanks can effectively withstand pressure fluctuations during operation, but higher design pressure requires thicker tank walls for the same volume, resulting in greater steel consumption and increased tank costs. Similarly, higher design pressure limits the volume of individual spherical tanks due to steel plate thickness restrictions, leading to a greater number of tanks needed for the same heat storage capacity, increasing the land area required for the thermal storage system and further increasing power plant investment. Furthermore, large-capacity compressed air energy storage power plants use large-volume, thick-walled tanks (for example, the tanks in the aforementioned 300MW compressed air energy storage demonstration project have a single tank volume of 3500m³). 3 (The storage tank wall thickness is 50mm). During operation, the repeated and large fluctuations in the pressure inside the storage tank will inevitably cause stress fatigue, which increases the operating risk of the storage tank and reduces its effective life.

[0006] Although the above problems can be solved by using stress analysis design and fatigue equipment design in the design stage, it will inevitably affect the design selection and design cycle of the storage tank, and will also inevitably increase certain costs.

[0007] Therefore, it is necessary to develop a near-constant pressure pressurized hot water thermal storage system and its operation method that can effectively reduce pressure fluctuations in high-temperature and low-temperature water tanks, alleviate stress fatigue in high-temperature and low-temperature water tanks, and improve the service life of high-temperature and low-temperature water tanks, while effectively reducing the design pressure and steel consumption of high-temperature and low-temperature water tanks, thereby reducing the total investment of the thermal storage system and achieving good economic benefits. Summary of the Invention

[0008] The primary objective of this invention is to overcome the shortcomings of the aforementioned background technology and provide a near-constant-pressure pressurized hot water thermal storage system. This addresses the problems of existing thermal storage systems using high-pressure, high-temperature hot water storage, such as significantly higher tank design pressure compared to the saturation pressure corresponding to the storage temperature, limited single tank volume, high steel consumption, and high cost, thereby further improving the economic efficiency of compressed air energy storage power station thermal storage systems. Furthermore, it addresses the issues of large pressure fluctuations, constant stress fatigue, and reduced service life of tanks in existing high-pressure, high-temperature hot water thermal storage systems, by further reducing tank design pressure and pressure fluctuations, mitigating stress fatigue, and extending tank service life. Finally, it addresses the problems of high design difficulty and long design cycles in existing high-pressure, high-temperature hot water thermal storage systems, reducing tank design difficulty and improving design efficiency.

[0009] The second objective of this invention is to provide an operating method for such a near-constant pressure pressurized hot water storage system.

[0010] To achieve the aforementioned first objective, the technical solution of the present invention is as follows: a near-constant pressure pressurized hot water storage system, comprising a pressurized hot water storage system A, wherein the pressurized hot water storage system A comprises at least one high-temperature water tank and at least one low-temperature water tank; the high-temperature water tank and the low-temperature water tank contain pressure-stabilizing gas, the high-temperature water tank and the low-temperature water tank are connected by a connecting pipe, the high-temperature water tank is connected to the low-temperature water tank through a high-temperature water circulation pump and at least one stage of expansion-side heat exchanger, and the low-temperature water tank is connected to the high-temperature water tank through a low-temperature water circulation pump and at least one stage of compression-side heat exchanger;

[0011] Its characteristic is that it also includes a pressure stabilization system B, which includes a buffer tank, a high-pressure gas storage tank, and a pressure-stabilizing gas pressurization system;

[0012] The buffer tank is connected to the connecting pipe, and the high-pressure gas storage tank is also connected to the connecting pipe; the pressure-stabilizing gas boosting system includes a pressure-stabilizing gas compressor, a pressure-stabilizing gas cooler, and a gas-water separator; the pressure-stabilizing gas compressor is connected to an electric motor;

[0013] The buffer tank is connected to the high-pressure gas storage tank in sequence through a pressure-stabilized gas compressor, a pressure-stabilized gas cooler, and a gas-water separator.

[0014] In the above technical solution, the pressure stabilization system B also includes a high and low temperature water tank venting and stabilizing system, which includes a buffer tank inlet cooler, and the connecting pipe is connected to the buffer tank through the buffer tank inlet cooler.

[0015] In the above technical solution, the pressure stabilization system B also includes a high and low temperature water tank gas injection and stabilization system, which includes a gas injection and stabilization pressure reducing valve. The high pressure storage tank is connected to the connecting pipe through the gas injection and stabilization pressure reducing valve.

[0016] In the above technical solution, the pressure-stabilizing gas boosting system also includes a recirculation pipeline, and a recirculation valve is provided on the recirculation pipeline; after the pressure-stabilizing gas cooler (320) is connected to the gas-water separator (330), one path is connected to the buffer tank (210) through the recirculation pipeline (340), and the other path is connected to the high-pressure gas storage tank (220).

[0017] In the above technical solution, the pressure stabilization system B also includes a condensate system, which includes a high-pressure gas storage tank drainage system, a pressure-stabilizing gas cooler drainage system, a gas-water separator drainage system, a buffer tank inlet cooler drainage system, and a condensate pump.

[0018] The high-pressure gas storage tank drainage system includes a first drain valve, through which the high-pressure gas storage tank is connected to a buffer tank; the pressure-stabilizing gas cooler drainage system includes a second drain valve, through which the pressure-stabilizing gas cooler is connected to the buffer tank; the gas-liquid separator drainage system includes a third drain valve, through which the gas-liquid separator is connected to the buffer tank; and the buffer tank inlet cooler drainage system includes a fourth drain valve, through which the buffer tank inlet cooler is connected to the buffer tank.

[0019] The buffer tank is connected to the cryogenic water tank via a condensate pump.

[0020] In the above technical solution, the pressure stabilization system B further includes a pressure-stabilizing gas replenishment system, which includes a pressure-stabilizing gas cylinder group connected to a high-pressure gas storage tank.

[0021] In the above technical solution, the low-temperature water circulation pump and the high-temperature water circulation pump are combined, and the compression-side heat exchanger and the expansion-side heat exchanger are combined.

[0022] In the above technical solution, at least two low-temperature water circulation pumps are provided, one of which is a spare; at least two high-temperature water circulation pumps are provided, one of which is a spare; at least two pressure-stabilizing gas compressors are provided, one of which is a spare; at least two electric motors are provided, one of which is a spare; at least two sets of recirculation pipelines are provided, one of which is a spare; at least two gas injection pressure-stabilizing and reducing valves are provided, one of which is a spare; and at least two condensate pumps are provided, one of which is a spare.

[0023] To achieve the aforementioned first objective, the technical solution of the present invention is: an operation method for a near-constant pressure pressurized hot water storage system, characterized by comprising the following steps:

[0024] Step 1, Compressed Energy Storage Stage:

[0025] The cryogenic water tank stores cryogenic water at its highest level, and the high-temperature water tank stores high-temperature water at its lowest level. The gas-side pressure in both the high-temperature and cryogenic water tanks is stable within a set range above the saturation pressure corresponding to the heat storage temperature. The gas release and pressure stabilization system of the high and low temperature water tanks is closed, and the pressure in the buffer tank is the same as the gas-side pressure of the cryogenic and high-temperature water tanks. The gas injection and pressure stabilization system of the high and low temperature water tanks is closed, and the high-pressure gas storage tank is filled with high-pressure stabilizing gas.

[0026] Start the cryogenic water circulation pump to pump the cryogenic water in the cryogenic water tank into the compression side heat exchanger for heating and raising the temperature to high temperature water before sending it to the high temperature water tank for storage. As the cryogenic water circulation pump runs, the level of cryogenic water in the cryogenic water tank continuously decreases, while the level of high temperature water in the high temperature water tank continuously increases. The high temperature stabilizing gas in the high temperature water tank is forced into the cryogenic water tank through the connecting pipe. The high temperature stabilizing gas is cooled down by the cryogenic water in the cryogenic water tank, and the gas-side pressure in both the high temperature water tank and the cryogenic water tank decreases.

[0027] When the pressure drops to the lower limit, the high and low temperature water tank gas injection and pressure stabilization system is turned on. The high pressure stabilizing gas in the high pressure storage tank is depressurized through the gas injection and pressure stabilizing valve and then reinjected into the connecting pipe. The flow rate of the reinjected stabilizing gas is matched with the rate of decrease of the gas side pressure to ensure that the gas side pressure of the high temperature water tank and the low temperature water tank is basically constant.

[0028] After the compression and energy storage phase is completed, the cryogenic water circulation pump is stopped, the cryogenic water tank stores the lowest level of cryogenic water, and the high-temperature water tank stores the highest level of high-temperature water; the high and low temperature water tank venting and pressure stabilizing system is closed, and the pressure in the buffer tank is the same as the gas-side pressure of the high-temperature water tank and the cryogenic water tank; the high and low temperature water tank gas injection and pressure stabilizing system is closed, and the pressure in the high-pressure gas storage tank decreases, but the pressure is still higher than the pressure in the high-temperature water tank, the cryogenic water tank, and the buffer tank;

[0029] Step 2, Settling Stage:

[0030] Closely monitor the gas-side pressure of the high-temperature water tank and the low-temperature water tank; the pressure of the pressure-stabilizing gas in the upper space of the low-temperature water tank will decrease as it is cooled by the low-temperature water; the pressure of the pressure-stabilizing gas in the upper space of the high-temperature water tank will increase as it is heated by the high-temperature water.

[0031] The high-temperature water tank and the low-temperature water tank are connected by a pipe to equalize the pressure, and the pressure will gradually decrease.

[0032] When the pressure drops to the lower limit, the high and low temperature water tank gas injection and pressure stabilization system is turned on. The high pressure stabilizing gas in the high pressure storage tank is depressurized through the gas injection and pressure stabilizing valve and then reinjected into the connecting pipe. The flow rate of the reinjected stabilizing gas is matched with the rate of decrease of the gas side pressure to ensure that the gas side pressure of the high temperature water tank and the low temperature water tank is basically constant.

[0033] Step 3, Expansion Power Generation Stage:

[0034] The low-temperature water tank stores the lowest level of low-temperature water, and the high-temperature water tank stores the highest level of high-temperature water. The gas-side pressure in both the high-temperature and low-temperature water tanks is stabilized within a set range above the saturation pressure corresponding to the heat storage temperature. When the high- and low-temperature water tank venting and pressure stabilizing system is opened, the pressure in the buffer tank is the same as the gas-side pressure in the low-temperature and high-temperature water tanks. When the high- and low-temperature water tank gas injection and pressure stabilizing system is closed, the high-pressure gas storage tank is filled with high-pressure stabilizing gas.

[0035] The high-temperature water circulation pump is started, pumping the high-temperature water in the high-temperature water tank into the expansion side heat exchanger for cooling and cooling into low-temperature water, which is then sent to the low-temperature water tank for storage. As the high-temperature water circulation pump runs, the liquid level in the high-temperature water tank continuously decreases, while the liquid level in the low-temperature water tank continuously increases. The low-temperature pressure-stabilizing gas in the low-temperature water tank is expelled into the high-temperature water tank through the connecting pipe. The low-temperature pressure-stabilizing gas is heated by the high-temperature water in the high-temperature water tank, increasing the gas-side pressure in both the high-temperature and low-temperature water tanks. The pressure-stabilizing gas in the high-temperature and low-temperature water tanks enters the high-low temperature water tank venting and pressure-stabilizing system through the connecting pipe, and after being cooled by the inlet cooler of the buffer tank, it enters the buffer tank.

[0036] When the pressure in the buffer tank rises to the set value, the pressure-stabilizing gas boosting system is activated. The pressure-stabilizing gas expelled into the buffer tank is first compressed by the pressure-stabilizing gas compressor, then cooled by the pressure-stabilizing gas cooler, and separated into liquid water by the gas-water separator before entering the high-pressure gas storage tank for storage, ensuring that the gas-side pressure of the high-temperature water tank, the low-temperature water tank, and the buffer tank remains basically constant.

[0037] When the flow rate of the pressure-stabilized gas squeezed into the buffer tank is small, the recirculation pipeline is started. The high-pressure pressure-stabilized gas at the outlet of the pressure-stabilized gas compressor is reduced by the recirculation valve and returned to the buffer tank, ensuring that the inlet flow rate of the pressure-stabilized gas compressor meets the minimum flow requirement.

[0038] After the expansion power generation stage is completed, the high-temperature water circulation pump is stopped, the low-temperature water tank stores the highest level of low-temperature water, and the high-temperature water tank stores the lowest level of high-temperature water; the high and low temperature water tank venting and pressure stabilizing system is closed, and the pressure in the buffer tank is the same as the gas-side pressure of the high-temperature water tank and the low-temperature water tank; the high and low temperature water tank gas injection and pressure stabilizing system is closed, and the pressure in the high-pressure gas storage tank increases.

[0039] Step 4, Settling Stage: Closely monitor the gas-side pressure of the high-temperature water tank and the low-temperature water tank; the pressure of the stabilizing gas in the upper space of the low-temperature water tank will decrease as it is cooled by the low-temperature water; the pressure of the stabilizing gas in the upper space of the high-temperature water tank will increase as it is heated by the high-temperature water.

[0040] The high-temperature water tank and the low-temperature water tank are connected by a pipe to equalize the pressure, and the pressure will gradually decrease.

[0041] When the pressure drops to the lower limit, the high and low temperature water tank gas injection and pressure stabilization system is turned on. The high pressure stabilizing gas in the high pressure storage tank is depressurized through the gas injection and pressure stabilizing valve and then reinjected into the connecting pipe. The flow rate of the reinjected stabilizing gas is matched with the rate of decrease of the gas side pressure to ensure that the gas side pressure of the high temperature water tank and the low temperature water tank is basically constant.

[0042] If the gas-side pressure of the high-temperature water tank and the low-temperature water tank increases due to other reasons during the settling process in steps 2 and 4, the pressure-stabilizing gas boosting system will be activated in step 3 to compress and store the displaced pressure-stabilizing gas, thereby ensuring that the gas-side pressure of the high-temperature water tank, the low-temperature water tank and the buffer tank remains basically constant.

[0043] The first cycle of the thermal storage system is completed by steps 1-4 above. Repeating steps 1-4 will allow for subsequent cycles of the thermal storage system.

[0044] In the above technical solution, in step 3, during operation, the pressure inside the high-pressure gas storage tank continuously increases. The output of the pressure-stabilizing gas compressor is adjusted by frequency conversion to meet the outlet pressure matching, and the pressure inside the high-pressure gas storage tank is maintained. At the same time, the condensate from the inlet cooler of the buffer tank, the condensate from the pressure-stabilizing gas cooler, and the condensate from the gas-water separator enter the buffer tank through their respective drains. When the condensate level in the buffer tank reaches the set value, the condensate pump is started to pump the condensate into the low-temperature water tank.

[0045] Compared with the prior art, the present invention has the following advantages:

[0046] 1) Compared with the existing high-pressure high-temperature hot water storage system, the present invention can effectively reduce the pressure fluctuation range of the gas side of high and low temperature water tanks (the pressure fluctuation range of this application is 0.05MPa, while the pressure fluctuation range of the existing high-pressure high-temperature hot water storage system is 0.5MPa), effectively alleviate the stress fatigue of high and low temperature water tanks, improve the service life and safety of high and low temperature water tanks, and the pressure fluctuation range is small, which does not fall into the category of fatigue equipment, and can further reduce the design difficulty and the measures to be taken, and reduce the cost of storage tanks.

[0047] 2) Because the pressure fluctuation range of the high and low temperature water tanks is small, the present invention can effectively reduce the design pressure of the high and low temperature water tanks, thereby reducing the wall thickness of the high and low temperature water tanks, reducing the steel consumption per unit volume of the high and low temperature water tanks, reducing the cost of the thermal storage system, and improving the economic indicators of the power plant.

[0048] 3) Because the pressure fluctuation range of the high and low temperature water tanks is small, this invention will not affect the design selection and design cycle of the high and low temperature water tanks, thereby reducing the design difficulty of the high and low temperature water tanks and improving the design efficiency. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the structure of the present invention.

[0050] Figure 2 This is a diagram showing the pressure fluctuations on the gas side of the high-temperature water tank and the low-temperature water tank in this invention.

[0051] Figure 3 This is a diagram showing the pressure fluctuations on the gas side of the high-temperature and low-temperature water tanks in an existing high-temperature and high-pressure hot water storage system.

[0052] Among them, A - pressurized hot water storage system, B - pressure stabilization system, 110 - high temperature water tank, 111 - high temperature water tank water-side shut-off valve, 112 - high temperature water tank gas-side shut-off valve, 120 - low temperature water tank, 121 - low temperature water tank water-side shut-off valve, 122 - low temperature water tank gas-side shut-off valve, 130 - connecting pipe, 141 - high temperature water circulation pump, 142 - low temperature water circulation pump, 151 - expansion side heat exchanger, 152 - compression side heat exchanger, 161 - first shut-off valve, 162 - second shut-off valve, 163 - third shut-off valve. Valves, 164-Fourth shut-off valve, 171-First check valve, 172-Second check valve, 181-First regulating valve, 182-Second regulating valve, 210-Buffer tank, 211-Fifth shut-off valve, 220-High-pressure gas storage tank, 221-Sixth shut-off valve, 300-Pressure-stabilized gas booster system, 310-Pressure-stabilized gas compressor, 311-Motor, 320-Pressure-stabilized gas cooler, 330-Gas-liquid separator, 340-Recirculation pipeline, 341-Recirculation valve, 351-Seventh shut-off valve, 352 - Eighth shut-off valve, 361- Third check valve, 400- High and low temperature water tank venting and pressure stabilizing system, 410- Buffer tank inlet cooler, 420- Ninth shut-off valve, 430- Fourth check valve, 500- High and low temperature water tank gas injection and pressure stabilizing system, 510- Gas injection and pressure stabilizing pressure reducing valve, 520- Tenth shut-off valve, 530- Fifth check valve, 600- Condensate system, 610- High pressure gas storage tank drainage system, 611- First steam trap, 612- Eleventh shut-off valve, 620- Pressure stabilizing gas cooler drainage system, 62 1-Second steam trap, 622-Twelfth shut-off valve, 630-Gas-water separator drain system, 631-Third steam trap, 632-Thirteenth shut-off valve, 640-Buffer tank inlet cooler drain system, 641-Fourth steam trap, 642-Fourteenth shut-off valve, 650-Condensate pump, 651-Fifteenth shut-off valve, 652-Sixth check valve, 653-Sixteenth shut-off valve, 700-Pressure stabilizing gas replenishment system, 710-Pressure stabilizing gas cylinder group, 720-Seventh check valve, 730-Seventeenth shut-off valve. Detailed Implementation

[0053] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but these descriptions are not intended to limit the invention and are merely illustrative. The advantages of the present invention will become clearer and easier to understand through this description.

[0054] Referring to the accompanying drawings, a near-constant-pressure pressurized hot water storage system includes a pressurized hot water storage system A. The pressurized hot water storage system A includes at least one high-temperature water tank 110 and at least one low-temperature water tank 120. Both the high-temperature water tank 110 and the low-temperature water tank 120 contain pressure-stabilizing gas. The tops of the high-temperature water tank 110 and the low-temperature water tank 120 are connected by a connecting pipe 130. The bottom of the high-temperature water tank 110 is connected sequentially by a high-temperature water tank water-side shut-off valve 111, a first shut-off valve 161, a high-temperature water circulation pump 141, and a first stop valve. The return valve 171, at least one expansion-side heat exchanger 151, first regulating valve 181, second shut-off valve 162, and low-temperature water tank water-side shut-off valve 121 are connected to the bottom of low-temperature water tank 120. The bottom of low-temperature water tank 120 is connected to high-temperature water tank 110 in sequence through low-temperature water tank water-side shut-off valve 121, third shut-off valve 163, low-temperature water circulation pump 142, second check valve 172, at least one compression-side heat exchanger 152, second regulating valve 182, fourth shut-off valve 164, and high-temperature water tank water-side shut-off valve 111.

[0055] A high-temperature water tank gas-side shut-off valve 112 is installed at the end of the connecting pipe 130 near the high-temperature water tank 110, and a low-temperature water tank gas-side shut-off valve 122 is installed at the end near the low-temperature water tank 120.

[0056] High-temperature water tank 110 and low-temperature water tank 120 are used to store high-temperature and low-temperature heat storage media in the power plant, respectively. Both high-temperature water tank 110 and low-temperature water tank 120 can be spherical tanks, C-type horizontal tanks, or vertical tanks. When the heat storage temperature is high, the design pressure of high-temperature water tank 110 and low-temperature water tank 120 is high, or the volume of high-temperature water tank 110 and low-temperature water tank 120 is large, spherical tanks are preferred. Connecting pipe 130 is used to connect high-temperature water tank 110 and low-temperature water tank 120 to keep the gas-side pressure in high-temperature water tank 110 and low-temperature water tank 120 balanced.

[0057] The cryogenic water circulation pump 142 is used to pump cryogenic water from the cryogenic water tank 120 into the compression-side heat exchanger 152 during the compression energy storage stage of the power plant. The cryogenic water absorbs heat and rises to high temperature in the compression-side heat exchanger 152 before entering the high temperature water tank 110 for storage. The high temperature water circulation pump 141 is used to pump high temperature water from the high temperature water tank 110 into the expansion-side heat exchanger 151 during the expansion power generation stage of the power plant. The high temperature water releases heat and cools down to cryogenic water in the expansion-side heat exchanger 151 before entering the cryogenic water tank 120 for storage. When the cryogenic water circulation pump 142 and the high temperature water circulation pump 141 are set separately, at least two of each should be set (one of which is a spare). The cryogenic water circulation pump 142 and the high temperature water circulation pump 141 can also be set together, with at least two of them (one of which is a spare).

[0058] The compression-side heat exchanger 152 is a device that cools the high-temperature air at the outlet of the power plant compressor and transfers the heat of the air to the low-temperature heat storage medium; the expansion-side heat exchanger 151 is a device that transfers the heat of the high-temperature heat storage medium to the low-temperature air at the inlet of the expander and heats the low-temperature air at the inlet of the expander into high-temperature air; the compression-side heat exchanger 152 and the expansion-side heat exchanger 151 can be selected from shell-and-tube heat exchangers, finned tube heat exchangers, hairpin heat exchangers, plate-fin heat exchangers, etc., depending on the parameters of the air medium; the compression-side heat exchanger 152 can also be combined with the expansion-side heat exchanger 151.

[0059] The function of a shut-off valve is to isolate the pipeline system, the function of a check valve is to prevent the backflow of the medium downstream of the valve, and the function of a regulating valve is to adjust the flow rate of the medium passing through the valve.

[0060] It also includes a pressure stabilization system B, which includes a buffer tank 210, a high-pressure gas storage tank 220, and a pressure-stabilizing gas boosting system 300.

[0061] The top of the buffer tank 210 is connected to the connecting pipe 130 via a fifth shut-off valve 211, and the top of the high-pressure gas storage tank 220 is connected to the connecting pipe 130 via a sixth shut-off valve 221; the pressure-stabilizing gas boosting system 300 includes a pressure-stabilizing gas compressor 310, a pressure-stabilizing gas cooler 320, and a gas-water separator 330; the pressure-stabilizing gas compressor 310 is connected to an electric motor 311;

[0062] The bottom side of the buffer tank 210 is connected to the bottom side of the high-pressure gas storage tank 220 in sequence through the seventh shut-off valve 351, the pressure-stabilizing gas compressor 310, the third check valve 361, the pressure-stabilizing gas cooler 320, the gas-water separator 330, and the eighth shut-off valve 352.

[0063] The pressure stabilization system B also includes a high and low temperature water tank venting and stabilizing system 400, which includes a buffer tank inlet cooler 410. The connecting pipe 130 is connected to the top of the buffer tank 210 in sequence through a ninth shut-off valve 420, a fourth check valve 430, a buffer tank inlet cooler 410, and a fifth shut-off valve 211.

[0064] The pressure stabilization system B also includes a high and low temperature water tank gas injection and stabilization system 500, which includes a gas injection and stabilization pressure reducing valve 510. The top of the high pressure storage tank 220 is connected to the connecting pipe 130 in sequence through a sixth shut-off valve 221, a gas injection and stabilization pressure reducing valve 510, a tenth shut-off valve 520, and a fifth check valve 530.

[0065] The pressure-stabilizing gas boosting system 300 also includes a recirculation pipeline 340, on which a recirculation valve 341 is provided; after the pressure-stabilizing gas cooler 320 is connected to the gas-water separator (330), one path is connected to the bottom side of the buffer tank 210 through the recirculation pipeline 340, and the other path is connected to the bottom side of the high-pressure gas storage tank 220.

[0066] The pressure stabilization system B also includes a condensate system 600, which includes a high-pressure gas storage tank drainage system 610, a pressure-stabilizing gas cooler drainage system 620, a gas-water separator drainage system 630, a buffer tank inlet cooler drainage system 640, and a condensate pump 650.

[0067] The high-pressure gas storage tank drainage system 610 includes a first drain 611, and the bottom of the high-pressure gas storage tank 220 is connected to the bottom of the buffer tank 210 in sequence via an eleventh shut-off valve 612 and the first drain 611; the pressure-stabilizing gas cooler drainage system 620 includes a second drain 621, and the pressure-stabilizing gas cooler 320 is connected to the bottom of the buffer tank 210 in sequence via a twelfth shut-off valve 622 and the second drain 621; the gas-liquid separator drainage system 630 includes a third drain 631, and the gas-liquid separator 330 is connected to the bottom of the buffer tank 210 in sequence via a thirteenth shut-off valve 632 and the third drain 631; the buffer tank inlet cooler drainage system 640 includes a fourth drain 641, and the buffer tank inlet cooler 410 is connected to the bottom of the buffer tank 210 in sequence via a fourteenth shut-off valve 642 and the fourth drain 641.

[0068] The bottom of the buffer tank 210 is connected to the bottom side of the low-temperature water tank 120 in sequence through the fifteenth shut-off valve 651, the condensate pump 650, the sixth check valve 652, and the sixteenth shut-off valve 653.

[0069] The pressure stabilization system B also includes a pressure-stabilizing gas replenishment system 700, which includes a pressure-stabilizing gas cylinder group 710. The pressure-stabilizing gas cylinder group 710 is connected to the bottom side of the high-pressure gas storage tank 220 in sequence through a seventh check valve 720 and a seventeenth shut-off valve 730.

[0070] Nitrogen is preferred as the pressure-stabilizing gas in the high-temperature water tank 110 and the low-temperature water tank 120.

[0071] At least two pressure-stabilizing gas compressors 310 are provided, one of which is a spare; at least two electric motors 311 are provided, one of which is a spare; at least two sets of recirculation pipelines 340 are provided, one of which is a spare; at least two gas injection pressure-stabilizing and reducing valves 510 are provided, one of which is a spare; and at least two condensate pumps 650 are provided, one of which is a spare.

[0072] The buffer tank 210 is used to store the pressure-stabilizing gas that is discharged when the gas-side pressure in the high-temperature water tank 110 and the low-temperature water tank 120 increases during power plant operation. Depending on the heat storage temperature and design pressure of the high-temperature water tank 110 and the low-temperature water tank 120, a spherical tank, a C-type horizontal tank, or a vertical tank can be selected. The design pressure of the buffer tank 210 is consistent with that of the high-temperature water tank 110 and the low-temperature water tank 120. The bottom space of the buffer tank 210 also serves as a condensate chamber, used to store the condensate of the pressure-stabilizing gas in the buffer tank 210, the condensate from the high-pressure gas storage tank 220, the condensate from the buffer tank inlet cooler 410, the condensate from the pressure-stabilizing gas cooler 320, and the condensate from the gas-water separator 330.

[0073] The high-pressure gas storage tank 220 is used to store high-pressure stabilized gas after being compressed and pressurized by the pressure-stabilized gas compressor 310. The volume of the high-pressure gas storage tank 220 is reduced by increasing the storage pressure of the stabilized gas, thereby reducing the cost. The high-pressure gas storage tank 220 can be a spherical tank or a C-type horizontal tank, with a spherical tank being preferred. A high-pressure gas storage tank drainage system 610 is installed at the bottom of the high-pressure gas storage tank 220, which transports the condensate in the high-pressure gas storage tank 220 to the buffer tank 210 through pipelines.

[0074] The function of the pressure-stabilizing gas boosting system 300 is to compress and boost the low-pressure stabilizing gas collected in the buffer tank 210 through the pressure-stabilizing gas compressor 310. The high-temperature and high-pressure stabilizing gas at the outlet of the pressure-stabilizing gas compressor 310 is cooled down by the pressure-stabilizing gas cooler 320, and then the liquid water is separated by the gas-liquid separator 330 before being sent to the high-pressure gas storage tank 220 for storage. The pressure-stabilizing gas compressor 310 can be a screw type or a centrifugal compressor depending on the system flow rate. The pressure-stabilizing gas compressor 310 adopts frequency conversion regulation to adapt to the pressure changes in the high-pressure gas storage tank 220.

[0075] The pressure-stabilizing gas cooler 320 is equipped with a pressure-stabilizing gas cooler condensate system 620, and the gas-water separator 330 is equipped with a gas-water separator condensate system 630. The condensate is transported to the buffer tank 210 through pipelines.

[0076] The recirculation line 340 is used to ensure the minimum inlet flow of the pressure-stabilizing gas compressor 310, while ensuring that the pressure in the buffer tank 210 remains basically constant to avoid excessive pressure fluctuations.

[0077] The function of the high and low temperature water tank venting and pressure stabilizing system 400 is to send the pressure-stabilizing gas that is discharged from the high temperature water tank 110 and the low temperature water tank 120 into the buffer tank 210 when the gas side pressure rises. The buffer tank inlet cooler 410 cools down the high temperature pressure-stabilizing gas discharged from the high temperature water tank 110 and the low temperature water tank 120, and at the same time condenses the water vapor carried in the pressure-stabilizing gas, so as to ensure the temperature of the pressure-stabilizing gas in the buffer tank 210 is stable and the amount of water carried is reduced, thus optimizing the intake conditions of the pressure-stabilizing gas compressor 310 and reducing the energy consumption of the pressure-stabilizing gas compressor 310.

[0078] The function of the high and low temperature water tank gas injection and pressure stabilization system 500 is to inject the pressure-stabilizing gas in the high pressure storage tank 220 back into the high temperature water tank 110 and the low temperature water tank 120 after the pressure on the gas side decreases through the gas injection and pressure stabilization valve 510, so as to ensure that the pressure on the gas side of the high temperature water tank 110 and the low temperature water tank 120 remains basically constant.

[0079] The condensate system 600 collects condensate from various systems in the buffer tank 210 (or a separate condensate storage tank can be installed), pressurizes it through the condensate pump 650, and then pumps it back to the low-temperature water tank 120 to ensure the water balance of the entire system and avoid excessive water replenishment, which would waste water resources. The function of the steam trap is to allow only condensate to pass through while preventing gas from passing through.

[0080] The function of the pressure-stabilizing gas replenishment system 700 is to provide pressure-stabilizing gas to the system before the first operation and to replenish the pressure-stabilizing gas lost due to leakage during the operation of the thermal storage system, so as to ensure the stability of the amount of pressure-stabilizing gas in the entire system.

[0081] Compressed air energy storage power stations generally operate as follows: During off-peak hours, the compressed air energy storage system is activated to absorb excess electricity from the grid, compressing the air and storing it in a gas storage tank; after the compressed air energy storage phase ends, the compressed air energy storage system is shut down, and the system enters a static phase; during peak hours, the expansion power generation system is activated, releasing high-pressure air from the gas storage tank into the expander to generate electricity; after the expansion power generation phase ends, the expansion power generation system is shut down, and the system enters a static phase. Depending on the peak and off-peak characteristics of the power grid, some power stations may experience multiple peak and off-peak periods in a day, and their operating modes are basically the same as described above, i.e., the compressed air energy storage system or the expansion power generation system is activated according to different peak and off-peak periods. This invention illustrates the system's operation mode using one peak and one off-peak period per day as an example:

[0082] An operation method for a near-constant pressure pressurized hot water storage system, characterized by the following steps:

[0083] Step 1, Compressed Energy Storage Stage:

[0084] The cryogenic water tank 120 stores cryogenic water at its highest level, and the high-temperature water tank 110 stores high-temperature water at its lowest level. The gas-side pressure in both the high-temperature water tank 110 and the cryogenic water tank 120 is maintained within a set range above the saturation pressure corresponding to the heat storage temperature (considering a range of saturation pressure +0.1-0.15 MPa). The high and low temperature water tank venting and pressure stabilizing system 400 is closed, and the pressure in the buffer tank 210 is the same as the gas-side pressure in the cryogenic water tank 120 and the high-temperature water tank 110. The high and low temperature water tank gas injection and pressure stabilizing system 500 is closed, and the high-pressure gas storage tank 220 is filled with high-pressure stabilizing gas.

[0085] The cryogenic water circulation pump 142 is started, and the cryogenic water in the cryogenic water tank 120 is pumped into the compression side heat exchanger 152 to be heated and heated to high temperature water, and then sent to the high temperature water tank 110 for storage. As the cryogenic water circulation pump 142 is running, the liquid level of the cryogenic water in the cryogenic water tank 120 continuously decreases, and the liquid level of the high temperature water in the high temperature water tank 110 continuously rises. The high temperature pressure stabilizing gas in the high temperature water tank 110 is squeezed into the cryogenic water tank 120 through the connecting pipe 130. The high temperature pressure stabilizing gas is cooled down by the cryogenic water in the cryogenic water tank 120, and the gas side pressure in the high temperature water tank 110 and the cryogenic water tank 120 decreases.

[0086] When the pressure drops to the lower limit (saturation pressure + 0.1 MPa), the high and low temperature water tank gas injection and pressure stabilization system 500 is turned on. The high pressure stabilizing gas in the high pressure storage tank 220 is depressurized by the gas injection and pressure stabilizing valve 510 and then reinjected into the connecting pipe 130. The reinjection stabilizing gas flow rate is matched with the gas side pressure reduction rate to ensure that the gas side pressure of the high temperature water tank 110 and the low temperature water tank 120 is basically constant (saturation pressure + 0.1-0.15 MPa range is considered).

[0087] After the compression and energy storage stage is completed, the cryogenic water circulation pump 142 is stopped. The cryogenic water tank 120 stores cryogenic water at the lowest liquid level, and the high-temperature water tank 110 stores high-temperature water at the highest liquid level. The high and low temperature water tank venting and pressure stabilizing system 400 is closed, and the pressure in the buffer tank 210 is the same as the gas-side pressure of the high-temperature water tank 110 and the cryogenic water tank 120. The high and low temperature water tank gas injection and pressure stabilizing system 500 is closed, and the pressure in the high-pressure gas storage tank 220 decreases, but the pressure is still higher than the pressure in the high-temperature water tank 110, the cryogenic water tank 120, and the buffer tank 210.

[0088] Step 2, Settling Stage:

[0089] Closely monitor the gas-side pressure of the high-temperature water tank 110 and the low-temperature water tank 120; the pressure of the pressure-stabilizing gas in the upper space of the low-temperature water tank 120 will decrease slightly due to the cooling effect of the low-temperature water; the pressure of the pressure-stabilizing gas in the upper space of the high-temperature water tank 110 will increase slightly due to the heating effect of the high-temperature water.

[0090] The high-temperature water tank 110 and the low-temperature water tank 120 are pressure-equalized through the connecting pipe 130, and the pressure will gradually decrease slightly.

[0091] When the pressure drops to the lower limit (saturation pressure + 0.1 MPa), the high and low temperature water tank gas injection and pressure stabilization system 500 is turned on. The high pressure stabilizing gas in the high pressure storage tank 220 is depressurized by the high pressure stabilizing gas injection and pressure stabilizing valve 510 and then reinjected into the connecting pipe 130. The reinjection pressure stabilizing gas flow rate is matched with the gas side pressure reduction rate to ensure that the gas side pressure of the high temperature water tank 110 and the low temperature water tank 120 is basically constant (considering the range of saturation pressure + 0.1-0.15 MPa).

[0092] Step 3, Expansion Power Generation Stage:

[0093] The cryogenic water tank 120 stores cryogenic water at its lowest level, and the high-temperature water tank 110 stores high-temperature water at its highest level. The gas-side pressure in both the high-temperature water tank 110 and the cryogenic water tank 120 is maintained within a set range above the saturation pressure corresponding to the heat storage temperature (considering a range of saturation pressure +0.1-0.15 MPa). The high and low temperature water tank venting and pressure stabilizing system 400 is opened, and the pressure in the buffer tank 210 is the same as the gas-side pressure in the cryogenic water tank 120 and the high-temperature water tank 110. The high and low temperature water tank gas injection and pressure stabilizing system 500 is closed, and the high-pressure gas storage tank 220 is filled with high-pressure stabilizing gas.

[0094] The high-temperature water circulation pump 141 is started, pumping the high-temperature water in the high-temperature water tank 110 into the expansion side heat exchanger 151 for cooling and cooling into low-temperature water, which is then sent to the low-temperature water tank 120 for storage. As the high-temperature water circulation pump 141 operates, the liquid level in the high-temperature water tank 110 continuously decreases, while the liquid level in the low-temperature water tank 120 continuously increases. The low-temperature pressure-stabilizing gas in the low-temperature water tank 120 is expelled into the high-temperature water tank 110 through the connecting pipe 130. The low-temperature pressure-stabilizing gas is heated by the high-temperature water in the high-temperature water tank 110, increasing the gas-side pressure in both the high-temperature water tank 110 and the low-temperature water tank 120. The pressure-stabilizing gas in the high-temperature water tank 110 and the low-temperature water tank 120 enters the high-low temperature water tank venting and pressure-stabilizing system 400 through the connecting pipe 130, and after being cooled by the buffer tank inlet cooler 410, it enters the buffer tank 210.

[0095] When the pressure in buffer tank 210 rises to the set value (saturation pressure + 0.15 MPa), the pressure-stabilizing gas boosting system 300 is activated. The pressure-stabilizing gas expelled into buffer tank 210 is first compressed by pressure-stabilizing gas compressor 310, then cooled by pressure-stabilizing gas cooler 320, and liquid water is separated by gas-liquid separator 330 before entering high-pressure gas storage tank 220 for storage, ensuring that the gas-side pressure of high-temperature water tank 110, low-temperature water tank 120 and buffer tank 210 remains basically constant (considering the range of saturation pressure + 0.1-0.15 MPa).

[0096] When the unit load rate is low or the liquid level change rate of the high temperature water tank 110 and low temperature water tank 120 is small during the start-up phase, the flow rate of the pressure-stabilizing gas discharged into the buffer tank 210 is small. The recirculation pipeline 340 is started, and the high pressure-stabilizing gas at the outlet of the pressure-stabilizing gas compressor 310 is reduced by the recirculation valve 341 and returned to the buffer tank 210 to ensure that the inlet flow rate of the pressure-stabilizing gas compressor 310 meets the minimum flow rate requirement.

[0097] During operation, the pressure inside the high-pressure gas storage tank 220 continuously increases. The power of the pressure-stabilizing gas compressor 310 is adjusted by frequency conversion to match the outlet pressure inside the high-pressure gas storage tank 220. At the same time, the condensate from the buffer tank inlet cooler 410, the pressure-stabilizing gas cooler 320, and the gas-water separator 330 enters the buffer tank 210 (or an independently set condensate storage tank) through their respective drains. When the condensate level in the buffer tank 210 (or the independently set condensate storage tank) reaches the set value, the condensate pump 650 is started to pump the condensate into the low-temperature water tank 120.

[0098] After the expansion power generation stage is completed, the high-temperature water circulation pump 141 is stopped, the low-temperature water tank 120 stores the highest level of low-temperature water, and the high-temperature water tank 110 stores the lowest level of high-temperature water; the high and low temperature water tank venting and pressure stabilizing system 400 is closed, and the pressure in the buffer tank 210 is stabilized; the high and low temperature water tank gas injection and pressure stabilizing system 500 is closed, and the pressure in the high-pressure gas storage tank 220 increases.

[0099] Step 4, Settling Stage: Closely monitor the gas-side pressure of the high-temperature water tank 110 and the low-temperature water tank 120; the pressure of the pressure-stabilizing gas in the upper space of the low-temperature water tank 120 will decrease as it is cooled by the low-temperature water; the pressure of the pressure-stabilizing gas in the upper space of the high-temperature water tank 110 will increase as it is heated by the high-temperature water.

[0100] The high-temperature water tank 110 and the low-temperature water tank 120 are pressure-equalized through the connecting pipe 130, and the pressure will gradually decrease.

[0101] When the pressure drops to the lower limit (saturation pressure + 0.1 MPa), the high and low temperature water tank gas injection and pressure stabilization system 500 is turned on. The high pressure stabilizing gas in the high pressure storage tank 220 is depressurized by the high pressure stabilizing gas injection and pressure stabilizing valve 510 and then reinjected into the connecting pipe 130. The reinjection pressure stabilizing gas flow rate is matched with the gas side pressure reduction rate to ensure that the gas side pressure of the high temperature water tank 110 and the low temperature water tank 120 is basically constant (considering the range of saturation pressure + 0.1-0.15 MPa).

[0102] If the gas-side pressure of the high-temperature water tank 110 and the low-temperature water tank 120 increases due to other reasons, the pressure-stabilizing gas boosting system 300 is started according to step 3 to compress and store the displaced pressure-stabilizing gas, thereby ensuring that the gas-side pressure of the high-temperature water tank 110, the low-temperature water tank 120 and the buffer tank 210 remains basically constant (considering the range of saturation pressure +0.1-0.15MPa).

[0103] The first cycle of the thermal storage system is completed by steps 1-4 above. Repeating steps 1-4 will allow for subsequent cycles of the thermal storage system.

[0104] Taking a thermal storage medium temperature of 180℃ and an operating mode consisting of an 8-hour compression energy storage phase, a 6-hour resting phase, a 5-hour expansion power generation phase, and a 5-hour resting phase as an example, the theoretically calculated fluctuation of the high and low temperature water tank gas-side pressure within a single cycle is as follows: Figure 2 As shown, the theoretically calculated fluctuations in the gas-side pressure of the high and low temperature water tanks in existing high-temperature and high-pressure hot water storage systems are as follows: Figure 3 As shown; by Figure 2 and Figure 3 It can be seen that the pressure fluctuation of the gas side of the high and low temperature water tanks in this invention is 0.05MPa, which is only one-tenth of the 0.5MPa pressure fluctuation of the high and low temperature water tanks in the existing high temperature and high pressure hot water storage system. The pressure fluctuation is greatly reduced, which greatly reduces the stress fatigue of the storage tank and improves the service life of the storage tank.

[0105] With a heat storage medium temperature of 180℃ and a single tank volume of 3500m³ 3 For example, the design parameters of the high and low temperature water tanks of this invention and existing high temperature and high pressure hot water storage systems are compared in the following table:

[0106] Tank design temperature ℃ 190 190 storage tank volume <![CDATA[ 3 ]]> 3500 3500 Tank Material / Q370R Q370R Tank design pressure MPa.g 1.15 1.6 Tank wall thickness mm 40 50 Tank weight t 390 490 Storage tank price Ten thousand yuan 770 980

[0107] As can be seen from the table above, the weight of a single spherical tank in this invention is reduced by 100 tons compared to existing high-temperature and high-pressure thermal storage systems, resulting in a cost reduction of 2.1 million yuan. Taking the thermal storage system of a 300MW compressed air energy storage power station demonstration project as an example, the entire station has a total of eight 3500m³ tanks. 3 The spherical tank, using this invention, can save 16.8 million yuan in construction costs for the spherical tank alone, resulting in significant economic benefits.

[0108] In summary, compared with existing high-pressure high-temperature hot water thermal storage systems, this invention effectively reduces the pressure fluctuation range of the gas side of high and low temperature water tanks, effectively alleviates stress fatigue in high and low temperature water tanks, improves the service life and safety of high and low temperature water tanks, and the pressure fluctuation range is relatively small, thus not falling into the category of fatigue equipment. This further reduces design difficulty and the measures required, and lowers the cost of storage tanks. Because the pressure fluctuation range of the high and low temperature water tanks is small, this invention can effectively reduce the design pressure of the high and low temperature water tanks, thereby reducing the wall thickness of the high and low temperature water tanks, reducing the steel consumption per unit volume of high and low temperature water tanks, lowering the cost of the thermal storage system, and improving the economic indicators of the power plant. Because the pressure fluctuation range of the high and low temperature water tanks is small, this invention will not affect the design selection and design cycle of high and low temperature water tanks, reducing the design difficulty of high and low temperature water tanks and improving design efficiency.

[0109] All other unspecified parts belong to the prior art.

Claims

1. A near-constant pressure pressurized hot water storage system, comprising a pressurized hot water storage system (A), wherein the pressurized hot water storage system (A) comprises at least one high-temperature water tank (110) and at least one low-temperature water tank (120); the high-temperature water tank (110) and the low-temperature water tank (120) contain pressure-stabilizing gas, the high-temperature water tank (110) and the low-temperature water tank (120) are connected by a connecting pipe (130), the high-temperature water tank (110) is connected to the low-temperature water tank (120) through a high-temperature water circulation pump (141) and at least one stage of expansion-side heat exchanger (151), and the low-temperature water tank (120) is connected to the high-temperature water tank (110) through a low-temperature water circulation pump (142) and at least one stage of compression-side heat exchanger (152); Its features are: It also includes a pressure stabilization system (B), which includes a buffer tank (210), a high-pressure gas storage tank (220), and a pressure-stabilizing gas boosting system (300); The buffer tank (210) is connected to the connecting pipe (130), and the high-pressure gas storage tank (220) is connected to the connecting pipe (130); the pressure-stabilizing gas boosting system (300) includes a pressure-stabilizing gas compressor (310), a pressure-stabilizing gas cooler (320), and a gas-water separator (330); the pressure-stabilizing gas compressor (310) is connected to an electric motor (311); The buffer tank (210) is connected to the high-pressure gas storage tank (220) in sequence through a pressure-stabilized gas compressor (310), a pressure-stabilized gas cooler (320), and a gas-water separator (330).

2. The near-constant pressure pressurized hot water storage system according to claim 1, characterized in that: The pressure stabilization system (B) further includes a high and low temperature water tank venting and stabilizing system (400), which includes a buffer tank inlet cooler (410). The connecting pipe (130) is connected to the buffer tank (210) through the buffer tank inlet cooler (410).

3. The near-constant pressure pressurized hot water storage system according to claim 2, characterized in that: The pressure stabilization system (B) further includes a high and low temperature water tank gas injection and stabilization system (500), which includes a gas injection and stabilization pressure reducing valve (510). The high pressure storage tank (220) is connected to the connecting pipe (130) through the gas injection and stabilization pressure reducing valve (510).

4. The near-constant pressure pressurized hot water storage system according to claim 3, characterized in that: The stable pressure gas pressurizing system (300) further comprises a recirculation pipeline (340) provided with a recirculation valve (341); the stable pressure gas cooler (320) is connected with the gas-water separator (330) and then connected with the buffer tank (210) through the recirculation pipeline (340) 、 The other way is connected with the high-pressure gas storage tank (220).

5. The near-constant pressure pressurized hot water storage system according to claim 4, characterized in that: The pressure stabilization system (B) further includes a condensate system (600), which includes a high-pressure gas storage tank drainage system (610), a pressure-stabilizing gas cooler drainage system (620), a gas-water separator drainage system (630), a buffer tank inlet cooler drainage system (640), and a condensate pump (650). The high-pressure gas storage tank drainage system (610) includes a first drain valve (611), and the high-pressure gas storage tank (220) is connected to the buffer tank (210) through the first drain valve (611); the pressure-stabilizing gas cooler drainage system (620) includes a second drain valve (621), and the pressure-stabilizing gas cooler (320) is connected to the buffer tank (210) through the second drain valve (621); the gas-liquid separator drainage system (630) includes a third drain valve (631), and the gas-liquid separator (330) is connected to the buffer tank (210) through the third drain valve (631); the buffer tank inlet cooler drainage system (640) includes a fourth drain valve (641), and the buffer tank inlet cooler (410) is connected to the buffer tank (210) through the fourth drain valve (641). The buffer tank (210) is connected to the low-temperature water tank (120) via a condensate pump (650).

6. The near-constant pressure pressurized hot water storage system according to claim 5, characterized in that: The pressure stabilization system (B) further includes a pressure-stabilizing gas replenishment system (700), which includes a pressure-stabilizing gas cylinder group (710) connected to a high-pressure gas storage tank (220).

7. The near-constant pressure pressurized hot water storage system according to claim 1, characterized in that: The low-temperature water circulation pump (142) and the high-temperature water circulation pump (141) are combined, and the compression-side heat exchanger (152) and the expansion-side heat exchanger (151) are combined.

8. A near-constant pressure pressurized hot water storage system according to claim 6, characterized in that: At least two low-temperature water circulation pumps (142) are provided, one of which is a spare; at least two high-temperature water circulation pumps (141) are provided, one of which is a spare; at least two pressure-stabilizing gas compressors (310) are provided, one of which is a spare; at least two electric motors (311) are provided, one of which is a spare; at least two sets of recirculation pipelines (340) are provided, one of which is a spare; at least two gas injection pressure-stabilizing and reducing valves (510) are provided, one of which is a spare; and at least two condensate pumps (650) are provided, one of which is a spare.

9. The operation method of the approximately constant pressure pressurized hot water storage system according to claim 6, characterized in that, Includes the following steps: Step 1, Compressed Energy Storage Stage: The cryogenic water tank (120) stores cryogenic water at its highest liquid level, and the high-temperature water tank (110) stores high-temperature water at its lowest liquid level. The gas-side pressure in both the high-temperature water tank (110) and the cryogenic water tank (120) is stable within a set range above the saturation pressure corresponding to the heat storage temperature. The high and low temperature water tank venting and pressure stabilizing system (400) is closed, and the pressure in the buffer tank (210) is the same as the gas-side pressure in the cryogenic water tank (120) and the high-temperature water tank (110). The high and low temperature water tank gas injection and pressure stabilizing system (500) is closed, and the high-pressure gas storage tank (220) is filled with high-pressure stabilizing gas. Start the low-temperature water circulation pump (142) to pump the low-temperature water in the low-temperature water tank (120) into the compression side heat exchanger (152) to heat it into high-temperature water and then send it into the high-temperature water tank (110) for storage; as the low-temperature water circulation pump (142) runs, the liquid level of the low-temperature water in the low-temperature water tank (120) continues to drop, and the liquid level of the high-temperature water in the high-temperature water tank (110) continues to rise. The high-temperature pressure-stabilizing gas in the high-temperature water tank (110) is squeezed into the low-temperature water tank (120) through the connecting pipe (130). The high-temperature pressure-stabilizing gas is cooled down by the low-temperature water in the low-temperature water tank (120), and the gas-side pressure in the high-temperature water tank (110) and the low-temperature water tank (120) decreases. When the pressure drops to the lower limit, the high and low temperature water tank gas injection and pressure stabilization system (500) is turned on. The high pressure stabilizing gas in the high pressure storage tank (220) is depressurized through the gas injection and pressure stabilizing valve (510) and then reinjected into the connecting pipe (130). The flow rate of the reinjected stabilizing gas is matched with the rate of decrease of the gas side pressure to ensure that the gas side pressure of the high temperature water tank (110) and the low temperature water tank (120) is basically constant. After the compression and energy storage stage is completed, the cryogenic water circulation pump (142) is stopped, the cryogenic water tank (120) stores the cryogenic water at the lowest liquid level, and the high-temperature water tank (110) stores the high-temperature water at the highest liquid level; the high and low temperature water tank venting and pressure stabilizing system (400) is closed, and the pressure in the buffer tank (210) is the same as the gas-side pressure of the high-temperature water tank (110) and the cryogenic water tank (120); the high and low temperature water tank gas injection and pressure stabilizing system (500) is closed, and the pressure in the high-pressure gas storage tank (220) decreases, but the pressure is still higher than the pressure in the high-temperature water tank (110), the cryogenic water tank (120), and the buffer tank (210); Step 2, Settling Stage: Closely monitor the gas-side pressure of the high-temperature water tank (110) and the low-temperature water tank (120); the pressure of the pressure-stabilizing gas in the upper space of the low-temperature water tank (120) will decrease as it is cooled by the low-temperature water; the pressure of the pressure-stabilizing gas in the upper space of the high-temperature water tank (110) will increase as it is heated by the high-temperature water. The high-temperature water tank (110) and the low-temperature water tank (120) are pressure-equalized through a connecting pipe (130), and the pressure will gradually decrease. When the pressure drops to the lower limit, the high and low temperature water tank gas injection and pressure stabilization system (500) is turned on. The high pressure stabilizing gas in the high pressure storage tank (220) is depressurized through the gas injection and pressure stabilizing valve (510) and then reinjected into the connecting pipe (130). The flow rate of the reinjected stabilizing gas is matched with the rate of decrease of the gas side pressure to ensure that the gas side pressure of the high temperature water tank (110) and the low temperature water tank (120) is basically constant. Step 3, Expansion Power Generation Stage: The low-temperature water tank (120) stores low-temperature water at the lowest liquid level, and the high-temperature water tank (110) stores high-temperature water at the highest liquid level. The gas-side pressure in the high-temperature water tank (110) and the low-temperature water tank (120) is stabilized within a set range above the saturation pressure corresponding to the heat storage temperature. The high-low temperature water tank venting and pressure stabilizing system (400) is opened, and the pressure in the buffer tank (210) is the same as the gas-side pressure in the low-temperature water tank (120) and the high-temperature water tank (110). The high-low temperature water tank gas injection and pressure stabilizing system (500) is closed, and the high-pressure gas storage tank (220) is filled with high-pressure stabilizing gas. Start the high-temperature water circulation pump (141) to pump the high-temperature water in the high-temperature water tank (110) into the expansion side heat exchanger (151) for cooling and cooling into low-temperature water, and then send it into the low-temperature water tank (120) for storage; as the high-temperature water circulation pump (141) runs, the liquid level in the high-temperature water tank (110) continuously decreases, and the liquid level in the low-temperature water tank (120) continuously rises. The low-temperature pressure-stabilizing gas in the low-temperature water tank (120) is squeezed into the high-temperature water tank (110) through the connecting pipe (130). The low-temperature pressure-stabilizing gas is heated by the high-temperature water in the high-temperature water tank (110), and the gas side pressure of the high-temperature water tank (110) and the low-temperature water tank (120) increases; the pressure-stabilizing gas in the high-temperature water tank (110) and the low-temperature water tank (120) enters the high-low temperature water tank venting and pressure stabilizing system (400) through the connecting pipe (130), and enters the buffer tank (210) after being cooled by the buffer tank inlet cooler (410); When the pressure in the buffer tank (210) rises to the set value, the pressure-stabilizing gas boosting system (300) is started. The pressure-stabilizing gas that is squeezed into the buffer tank (210) is first compressed by the pressure-stabilizing gas compressor (310), then cooled by the pressure-stabilizing gas cooler (320) and separated into liquid water by the gas-water separator (330) before entering the high-pressure gas storage tank (220) for storage, so as to ensure that the gas side pressure of the high-temperature water tank (110), the low-temperature water tank (120) and the buffer tank (210) is basically constant. When the flow rate of the pressure-stabilized gas squeezed into the buffer tank (210) is small, the recirculation pipeline (340) is started. The high-pressure pressure-stabilized gas at the outlet of the pressure-stabilized gas compressor (310) is reduced by the recirculation valve (341) and returned to the buffer tank (210), ensuring that the inlet flow rate of the pressure-stabilized gas compressor (310) meets the minimum flow rate requirement. After the expansion power generation stage is completed, the high-temperature water circulation pump (141) is stopped, the low-temperature water tank (120) stores the highest level of low-temperature water, and the high-temperature water tank (110) stores the lowest level of high-temperature water; the high and low temperature water tank venting and pressure stabilizing system (400) is closed, and the pressure in the buffer tank (210) is the same as the gas-side pressure of the high-temperature water tank (110) and the low-temperature water tank (120); the high and low temperature water tank gas injection and pressure stabilizing system (500) is closed, and the pressure in the high-pressure gas storage tank (220) increases; Step 4, settling stage: closely monitor the gas-side pressure of the high-temperature water tank (110) and the low-temperature water tank (120); the pressure of the stabilizing gas in the upper space of the low-temperature water tank (120) will decrease as it is cooled by the low-temperature water; the pressure of the stabilizing gas in the upper space of the high-temperature water tank (110) will increase as it is heated by the high-temperature water. The high-temperature water tank (110) and the low-temperature water tank (120) are pressure-equalized through a connecting pipe (130), and the pressure will gradually decrease. When the pressure drops to the lower limit, the high and low temperature water tank gas injection and pressure stabilization system (500) is turned on. The high pressure stabilizing gas in the high pressure storage tank (220) is depressurized through the gas injection and pressure stabilizing valve (510) and then reinjected into the connecting pipe (130). The flow rate of the reinjected stabilizing gas is matched with the rate of decrease of the gas side pressure to ensure that the gas side pressure of the high temperature water tank (110) and the low temperature water tank (120) is basically constant. If the gas-side pressure of the high-temperature water tank (110) and the low-temperature water tank (120) increases due to other reasons during the settling process in steps 2 and 4, the pressure-stabilizing gas boosting system (300) will be started in step 3 to compress and store the displaced pressure-stabilizing gas, thereby ensuring that the gas-side pressure of the high-temperature water tank (110), the low-temperature water tank (120) and the buffer tank (210) remains basically constant. The first cycle of the thermal storage system is completed by steps 1-4 above. Repeating steps 1-4 will allow for subsequent cycles of the thermal storage system.

10. The operation method of the approximately constant pressure pressurized hot water storage system according to claim 9, characterized in that, In step 3, during operation, the pressure inside the high-pressure gas storage tank (220) continuously increases. The output of the pressure-stabilizing gas compressor (310) is adjusted by frequency conversion to match the outlet pressure inside the high-pressure gas storage tank (220). At the same time, the condensate from the inlet cooler (410), the condensate from the pressure-stabilizing gas cooler (320), and the condensate from the gas-water separator (330) enter the buffer tank (210) through their respective drains. When the condensate level in the buffer tank (210) reaches the set value, the condensate pump (650) is started to pump the condensate into the low-temperature water tank (120).

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