Approximate constant pressure type pressurized hot water heat storage system and operation method thereof

Abstract

The invention discloses an approximate constant pressure type pressurized hot water heat storage system, and relates to the technical field of heat storage systems of compressed air energy storage power stations. The system comprises an under-pressure hot water heat storage system, and the under-pressure hot water heat storage system comprises a high-temperature water tank and a low-temperature water tank; the high-temperature water tank and the low-temperature water tank are filled with pressure-stabilizing gas and are connected through a communicating pipe; the pressure stabilizing system B comprises a buffer tank, a high-pressure gas storage tank and a pressure stabilizing gas pressurization system; the buffer tank is connected with the communicating pipe, and the high-pressure gas storage tank is connected with the communicating pipe. Compared with a high-pressure and high-temperature hot water heat storage system in the prior art, the air side pressure fluctuation range of the high-temperature water tank and the low-temperature water tank can be effectively reduced, stress fatigue of the high-temperature water tank and the low-temperature water tank is effectively relieved, the service life of the high-temperature water tank and the low-temperature water tank is prolonged, safety is improved, design difficulty and adopted measures are reduced, and the manufacturing cost of the storage tank is reduced. The invention further relates to an operation method of the approximate constant pressure type pressurized hot water heat storage system.

Description

Technical Field

[0001] The present invention relates to the technical field of heat storage systems of compressed air energy storage power stations, and more specifically to a near constant pressure hot water heat storage system. The present invention also relates to an operation method of the near constant pressure hot water heat storage system. Background Art

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

[0003] The compressed air energy storage system includes a compression energy storage system, an expansion power generation system, a heat storage system, a heat exchange system and a gas storage system; the main technical indicators of the compressed air energy storage power station include cost and electric-to-electric conversion efficiency; according to relevant research, under the same boundary conditions, with the increase of heat storage temperature, the system electric-to-electric conversion efficiency gradually increases; but with the increase of heat storage temperature, it brings a problem that cannot be ignored, that is, the applicability and economy of the heat storage medium; the current mainstream system solution to increase the heat storage temperature is to use heat transfer oil or molten salt as the heat storage medium, but heat transfer oil has problems such as high cost, toxic medium and safety risks; the cost of molten salt is greatly reduced compared to heat transfer oil, but relative to the entire power station investment, its investment proportion cannot be ignored. In addition, the liquid molten salt has a high freezing point, and there is a risk of condensation during the start-up and shutdown stages of the power station and during the shutdown of the power station, which has a huge impact on the safe and stable operation of the power station; it can be seen that the choice of heat storage system for compressed air energy storage power stations directly determines the economy and efficiency of the power station.

[0004] In order to solve the above problems, the applicant applied for patents such as "Compressed air energy storage system using high-pressure and high-temperature hot water to store heat" (application number: 202123240965.2), "A pressure self-balancing high-temperature hot water heat storage system and its operation method" (application number: 202111476481.1), and "Compressed air energy storage system using high-pressure and high-temperature hot water to store heat and its operation method" (application number: 202111577916.X). A pressure self-balancing heat storage system using pressurized hot water as the heat storage medium was proposed. The pressurized water is cleverly used as the heat storage medium, which can effectively increase the heat storage temperature and thus improve the heat storage efficiency. High system electric-to-electric conversion efficiency, while avoiding the high investment, toxic medium and safety risks, and easy condensation when using thermal oil and molten salt as heat storage media; the heat storage system and solution proposed in the above patent have been demonstrated in many large-capacity compressed air energy storage power stations under construction and planned in China; among them, a 300MW compressed air energy storage power station demonstration project has been built by the applicant's EPC general contracting. The project was connected to the grid for the first time on April 9, 2024, and passed half-capacity trial operation on July 28, 2024, fully verifying the feasibility and effectiveness of the compressed air energy storage power station using a pressurized hot water heat storage system.

[0005] In order to ensure that the hot water is always in liquid state during operation and to avoid the hot water in the tank from vaporizing, the pressurized hot water storage system uses pressurized gas to maintain the gas pressure in the tank not lower than the saturated pressure corresponding to the heat storage temperature (taking the 180°C heat storage temperature case proposed in the above patent as an example, the corresponding saturated pressure is 1.0MPa); at the same time, in order to cope with the pressure fluctuations caused by the change of liquid level in the storage tank, the maximum pressure of the designed high-temperature water tank and low-temperature water tank are both greater than the saturated pressure corresponding to the heat storage temperature (taking the 180°C heat storage temperature case proposed in the above patent as an example, the maximum pressure of the storage tank is not less than 1.5MPa); it can be seen from the above that the design pressure of the storage tank of this system solution is greater than the saturated pressure corresponding to the heat storage temperature of the storage tank. force; the higher the design pressure of the storage tank, the more it can withstand the pressure fluctuations during operation. However, the higher the design pressure, the thicker the design wall thickness of the storage tank of the same volume, and the greater the steel consumption of the storage tank, which brings the problem of increased tank cost; similarly, the higher the design pressure, the smaller the volume that a single spherical tank can achieve due to the thickness limit of the steel plate used for the spherical tank. Therefore, on the basis of the same amount of hot water stored, the more spherical tanks are required, and the larger the area occupied by the heat storage system, which will further increase the investment in the power station; in addition, the storage tanks used in large-capacity compressed air energy storage power stations have large volumes and thick walls (taking the storage tanks of a certain 300MW compressed air energy storage power station demonstration project built above as an example, the volume of a single tank is 3500m 3 , tank wall thickness 50mm), the repeated and large fluctuations in the pressure inside the tank during operation will inevitably cause stress fatigue to the tank, increase the operating risk of the tank, and reduce the effective life of the tank.

[0006] Although the above problems can be solved by adopting 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 inevitably increase certain costs.

[0007] Therefore, it is very necessary to develop an approximately constant pressure pressurized hot water heat storage system and its operation method which can effectively reduce the pressure fluctuation in the high-temperature water tank and the low-temperature water tank, alleviate the stress fatigue of the high-temperature water tank and the low-temperature water tank, and increase the service life of the high-temperature water tank and the low-temperature water tank on the basis of ensuring the safe and stable operation of the heat storage system, while effectively reducing the design pressure of the high-temperature water tank and the low-temperature water tank, reducing the steel consumption of the high-temperature water tank and the low-temperature water tank, and thereby reducing the total investment of the heat storage system, and having good economic benefits. Summary of the invention

[0008] The first purpose of the present invention is to overcome the shortcomings of the above-mentioned background technology and provide an approximately constant pressure pressurized hot water heat storage system; to solve the problems that the design pressure of the tank of the heat storage system using high-pressure and high-temperature hot water heat storage in the prior art is much higher than the saturation pressure corresponding to the heat storage temperature, the volume of a single tank is limited, the steel consumption of the tank is large, and the cost is high, and further improve the economy of the compressed air energy storage power station heat storage system; to solve the problems that the pressure fluctuation range of the tank of the heat storage system using high-pressure and high-temperature hot water heat storage in the prior art is large during operation, the tank is always subjected to stress fatigue, and the service life is affected, and further reduce the design pressure and pressure fluctuation of the tank, reduce stress fatigue, and increase the service life of the tank; to solve the problems that the tank design of the heat storage system using high-pressure and high-temperature hot water heat storage in the prior art is difficult and the design cycle is long, reduce the difficulty of tank design, and improve design efficiency.

[0009] The second object of the present invention is to provide an operating method for the approximately constant pressure pressurized hot water storage system.

[0010] In order to achieve the above-mentioned first purpose, the technical solution of the present invention is: a nearly constant pressure hot water heat storage system, including a hot water heat storage system A, wherein the hot water heat storage system A includes 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 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 compression side heat exchanger;

[0011] It is characterized in that: it also includes a pressure stabilization system B, and the pressure stabilization system B includes a buffer tank, a high-pressure gas storage tank, and a pressure-stabilizing gas boosting system;

[0012] The buffer tank is connected to the connecting pipe, and the high-pressure gas storage tank is 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 the motor;

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

[0014] In the above technical solution, the pressure stabilization system B also includes a high and low temperature water tank air venting and pressure stabilization system, and the high and low temperature water tank air venting and pressure stabilization system 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 pressure stabilization system, and the high and low temperature water tank gas injection and pressure stabilization system includes a gas injection pressure stabilizing and reducing valve, and the high-pressure gas storage tank is connected to the connecting pipe through the gas injection pressure stabilizing and reducing valve.

[0016] In the above technical solution, the pressure-stabilizing gas boosting system further comprises a recirculation pipeline, on which a recirculation valve is arranged; 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 drain system, a pressure-stabilizing gas cooler drain system, a gas-water separator drain system, a buffer tank inlet cooler drain system and a condensate pump;

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

[0019] The buffer tank is connected to the low-temperature water tank through a condensate pump.

[0020] In the above technical solution, the pressure stabilization system B also includes a pressure-stabilizing gas replenishing system, and the pressure-stabilizing gas replenishing system includes a pressure-stabilizing gas bottle group, and the pressure-stabilizing gas bottle group is connected to the 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 arranged in combination, and the compression side heat exchanger and the expansion side heat exchanger are arranged in combination.

[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] In order to achieve the above first objective, the technical solution of the present invention is: an operation method of a nearly constant pressure hot water storage system, characterized in that it includes the following steps:

[0024] Step 1, compression energy storage stage:

[0025] 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 gas-side pressures in the high-temperature and low-temperature water tanks are both stable within the set range above the saturation pressure corresponding to the heat storage temperature; the high- and low-temperature water tanks’ gas discharge and pressure stabilization systems are closed, and the pressure in the buffer tank is the same as the gas-side pressures in the low-temperature and high-temperature water tanks; the high- and low-temperature water tanks’ gas injection and pressure stabilization systems are closed, and the high-pressure gas storage tank is filled with high-pressure stabilizing gas;

[0026] Start the low-temperature water circulation pump, pump the low-temperature water in the low-temperature water tank into the compression side heat exchanger to heat it into high-temperature water, and then send it to the high-temperature water tank for storage; with the operation of the low-temperature water circulation pump, the liquid level of the low-temperature water in the low-temperature water tank continues to decrease, and the liquid level of the high-temperature water in the high-temperature water tank continues to increase, and the high-temperature pressure-stabilizing gas in the high-temperature water tank is squeezed into the low-temperature water tank through the connecting pipe, and the high-temperature pressure-stabilizing gas is cooled by the low-temperature water in the low-temperature water tank, and the pressure on the gas side of the high-temperature water tank and the low-temperature water tank is reduced;

[0027] When the pressure drops to the lower limit, open the high and low temperature water tank gas injection and pressure stabilization system, and inject the high pressure stabilization gas in the high pressure gas storage tank back into the connecting pipe after reducing the pressure through the gas injection and pressure stabilization pressure reducing valve. The flow rate of the back injection stabilization gas matches the pressure reduction rate on the gas side to ensure that the pressure on the gas side of the high temperature water tank and the low temperature water tank is basically constant.

[0028] After the compression energy storage stage is completed, the low-temperature water circulation pump is stopped, the low-temperature water at the lowest liquid level is stored in the low-temperature water tank, and the high-temperature water at the highest liquid level is stored in the high-temperature water tank; the high- and low-temperature water tanks’ air discharge and pressure stabilization systems are closed, and the pressure in the buffer tank is the same as the pressure on the gas side of the high-temperature water tank and the low-temperature water tank; the high- and low-temperature water tanks’ air injection and pressure stabilization systems are closed, and the pressure in the high-pressure gas storage tank is reduced, but the pressure is still higher than the pressure in the high-temperature water tank, the low-temperature water tank, and the buffer tank;

[0029] Step 2, static stage:

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

[0031] The high-temperature water tank and the low-temperature water tank are pressure-equalized through the connecting pipe, and the pressure will gradually decrease;

[0032] When the pressure drops to the lower limit, open the high and low temperature water tank gas injection and pressure stabilization system, and inject the high pressure stabilization gas in the high pressure gas storage tank back into the connecting pipe after reducing the pressure through the gas injection and pressure stabilization pressure reducing valve. The flow rate of the back injection stabilization gas matches the pressure reduction rate on the gas side to ensure that the pressure on the gas side 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 low-temperature water at the lowest liquid level, and the high-temperature water tank stores high-temperature water at the highest liquid level. The gas-side pressure in the high-temperature and low-temperature water tanks is stable within the set range above the saturation pressure corresponding to the heat storage temperature; the high- and low-temperature water tanks’ air discharge and pressure stabilization system is turned on, and the pressure in the buffer tank is the same as the gas-side pressure in the low-temperature and high-temperature water tanks; the high- and low-temperature water tanks’ air injection and pressure stabilization system is turned off, and the high-pressure gas storage tank is filled with high-pressure stabilization gas;

[0035] Start the high-temperature water circulation pump, pump the high-temperature water in the high-temperature water tank into the expansion side heat exchanger to cool it down into low-temperature water, and then send it to the low-temperature water tank for storage; with the operation of the high-temperature water circulation pump, the liquid level of the high-temperature water tank continues to drop, and the liquid level of the low-temperature water tank continues to rise, and the low-temperature pressure-stabilizing gas in the low-temperature water tank is squeezed into the high-temperature water tank through the connecting pipe, and the low-temperature pressure-stabilizing gas is heated by the high-temperature water in the high-temperature water tank, and the pressure on the gas side of the high-temperature water tank and the low-temperature water tank increases; the pressure-stabilizing gas in the high-temperature water tank and the low-temperature water tank enters the high-temperature and low-temperature water tank gas discharge and pressure-stabilizing system through the connecting pipe, and enters the buffer tank after being cooled by the buffer tank inlet cooler;

[0036] When the pressure in the buffer tank rises to the set value, the pressure-stabilizing gas boosting system is started; the pressure-stabilizing gas that is squeezed into the buffer tank is first compressed by the pressure-stabilizing gas compressor, then cooled by the pressure-stabilizing gas cooler, and separated from the liquid water by the gas-water separator before entering the high-pressure gas storage tank for storage, ensuring that the pressures on the high-temperature water tank, low-temperature water tank and gas side of the buffer tank are basically constant;

[0037] When the flow rate of the pressure-stabilizing gas expelled into the buffer tank is small, the recirculation pipeline is started, and part of the high-pressure pressure-stabilizing gas at the outlet of the pressure-stabilizing gas compressor is decompressed by the recirculation valve and then returned to the buffer tank, ensuring that the intake flow rate of the pressure-stabilizing gas compressor meets the minimum flow rate requirement;

[0038] After the expansion power generation stage is completed, the high-temperature water circulation pump is stopped, the low-temperature water with the highest liquid level is stored in the low-temperature water tank, and the high-temperature water with the lowest liquid level is stored in the high-temperature water tank; the high- and low-temperature water tank air discharge and pressure stabilization 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 air injection and pressure stabilization system is closed, and the pressure of the high-pressure gas storage tank increases;

[0039] Step 4, static stage: closely monitor the gas side pressure of the high-temperature water tank and the low-temperature water tank; the pressure-stabilizing gas in the upper space of the low-temperature water tank is cooled by the low-temperature water, and the pressure will decrease; the pressure-stabilizing gas in the upper space of the high-temperature water tank is heated by the high-temperature water, and the pressure will increase;

[0040] The high-temperature water tank and the low-temperature water tank are pressure-equalized through the connecting pipe, and the pressure will gradually decrease;

[0041] When the pressure drops to the lower limit, open the high and low temperature water tank gas injection and pressure stabilization system, and inject the high pressure stabilization gas in the high pressure gas storage tank back into the connecting pipe after reducing the pressure through the gas injection and pressure stabilization pressure reducing valve. The flow rate of the back injection stabilization gas matches the pressure reduction rate on the gas side to ensure that the pressure on the gas side of the high temperature water tank and the low temperature water tank is basically constant.

[0042] During the static process of step 2 and step 4, if the gas side pressure of the high temperature water tank and the low temperature water tank increases due to other reasons, start the pressure stabilizing gas boosting system 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, the low temperature water tank and the buffer tank is basically constant;

[0043] The first cycle of the heat storage system is completed through the above steps 1-4, and the subsequent cycles of the heat storage system can be carried out by repeating steps 1-4.

[0044] In the above technical scheme, in step 3, during operation, the pressure in the high-pressure gas storage tank continues to increase, and the output of the pressure-stabilizing gas compressor is adjusted by frequency conversion to meet the outlet pressure matching and the pressure in the high-pressure gas storage tank; at the same time, the condensate of the buffer tank inlet cooler, the condensate of the pressure-stabilizing gas cooler, and the condensate of the gas-water separator enter the buffer tank through their respective steam traps; 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 high-pressure, high-temperature, hot water heat storage system in the prior art, the present invention can effectively reduce the gas side pressure fluctuation range of the high and low temperature water tanks (the pressure fluctuation range of the present application is 0.05MPa, and the pressure fluctuation range of the high-pressure, high-temperature, hot water heat storage system in the prior art is 0.5MPa), effectively alleviate the stress fatigue of the high and low temperature water tanks, and improve the service life and safety of the high and low temperature water tanks. The pressure fluctuation range is small and does not belong to the category of fatigue equipment, which can further reduce the design difficulty and measures taken, and reduce the cost of storage tanks.

[0047] 2) Since the pressure fluctuation range of the high and low temperature water tanks is relatively 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 heat storage system, and improving the economic indicators of the power station.

[0048] 3) Since the pressure fluctuation range of the high and low temperature water tanks is small, the present 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. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0050] Figure 2 It is a gas side pressure fluctuation diagram of the high temperature water tank and the low temperature water tank in the present invention.

[0051] Figure 3 This is a gas side pressure fluctuation diagram of the high temperature water tank and the low temperature water tank in the existing high temperature and high pressure hot water thermal 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 valve, 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-stabilizing gas boosting system, 310-pressure-stabilizing gas compressor, 311-motor, 320-pressure-stabilizing gas cooler, 330-gas-water 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 and reducing valve, 520-tenth shut-off valve, 530-fifth check valve, 600-condensate system, 610-high pressure gas storage tank drain system, 611-first drain trap, 612-eleventh shut-off valve, 620-pressure stabilizing gas cooler drain system, 62 1-the second steam trap, 622-the twelfth shut-off valve, 630-the gas-water separator drain system, 631-the third steam trap, 632-the thirteenth shut-off valve, 640-the buffer tank inlet cooler drain system, 641-the fourth steam trap, 642-the fourteenth shut-off valve, 650-the condensate pump, 651-the fifteenth shut-off valve, 652-the sixth check valve, 653-the sixteenth shut-off valve, 700-the pressure-stabilizing gas replenishment system, 710-the pressure-stabilizing gas bottle group, 720-the seventh check valve, 730-the seventeenth shut-off valve. DETAILED DESCRIPTION

[0053] The following detailed description of the implementation of the present invention is made in conjunction with the accompanying drawings, but they do not constitute a limitation of the present invention and are only given as examples. At the same time, the advantages of the present invention will become clearer and easier to understand through the description.

[0054] Referring to the attached drawings, it can be seen that: an approximately constant pressure hot water heat storage system includes a hot water heat storage system A, wherein the hot water heat storage system A includes 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 top of the high temperature water tank 110 and the top of the low temperature water tank 120 are connected by a connecting pipe 130, and the bottom of the high temperature water tank 110 is connected in sequence 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, a first stop valve 162, a high temperature water circulation pump 142, a first stop valve 163, a high temperature water circulation pump 143, a first stop valve 164, a high temperature water circulation pump 144, a high temperature water circulation pump 145, a high temperature water circulation pump 146, a high temperature water circulation pump 147, a high temperature water circulation pump 148, a high temperature water circulation pump 149, a high temperature water circulation pump 149, a high temperature water circulation pump 141, a high temperature water circulation pump 142, a high temperature water circulation pump 143, a high temperature water circulation pump 144, a high temperature water circulation pump 145, a high temperature water circulation pump 146, a high temperature water circulation pump 147, a high temperature water circulation pump 148, a high temperature water circulation pump 149, a high temperature water circulation pump 140, a high temperature water circulation pump 141, a high temperature water circulation pump 142, a high temperature water circulation pump 143, a high temperature water circulation pump 144, a high temperature water circulation pump 145, a high temperature water circulation pump 146, a high temperature water circulation pump 146, a high temperature water circulation pump 146, a high temperature water circulation The return valve 171, at least one expansion side heat exchanger 151, the first regulating valve 181, the second shut-off valve 162, and the low temperature water tank water side shut-off valve 121 are connected to the bottom of the low temperature water tank 120, and the bottom of the low temperature water tank 120 is connected to the high temperature water tank 110 in sequence through the low temperature water tank water side shut-off valve 121, the third shut-off valve 163, the low temperature water circulation pump 142, the second check valve 172, at least one compression side heat exchanger 152, the second regulating valve 182, the fourth shut-off valve 164, and the high temperature water tank water side shut-off valve 111;

[0055] A high-temperature water tank gas-side shutoff valve 112 is provided at one end of the connecting pipe 130 close to the high-temperature water tank 110, and a low-temperature water tank gas-side shutoff valve 122 is provided at one end close to the low-temperature water tank 120;

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

[0057] The low-temperature water circulation pump 142 is used to pump the low-temperature water in the low-temperature water tank 120 into the compression side heat exchanger 152 during the compression energy storage stage of the power station. The low-temperature water absorbs heat and heats up to high-temperature water in the compression side heat exchanger 152, and then enters the high-temperature water tank 110 for storage; the high-temperature water circulation pump 141 is used to pump the high-temperature water in the high-temperature water tank 110 into the expansion side heat exchanger 151 during the expansion and power generation stage of the power station. The high-temperature water releases heat and cools down to low-temperature water in the expansion side heat exchanger 151, and then enters the low-temperature water tank 120 for storage; when the low-temperature water circulation pump 142 and the high-temperature water circulation pump 141 are separately arranged, at least two of each are arranged (one of which is a spare), and the low-temperature water circulation pump 142 and the high-temperature water circulation pump 141 can also be combined, 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 station 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 expander inlet and heats the low-temperature air at the expander inlet into high-temperature air; the compression side heat exchanger 152 and the expansion side heat exchanger 151 can select shell and tube heat exchangers, fin-tube heat exchangers, hairpin heat exchangers, plate-fin heat exchangers, etc. according to 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 the shut-off valve is to isolate the piping system, the function of the check valve is to prevent the medium from flowing back after the valve, and the function of the regulating valve is to adjust the medium flow 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 through the fifth shut-off valve 211, and the top of the high-pressure gas storage tank 220 is connected to the connecting pipe 130 through the 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 the 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 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 in sequence.

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

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

[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 further includes a condensate system 600, which includes a high-pressure gas storage tank drain system 610, a pressure-stabilizing gas cooler drain system 620, a gas-water separator drain system 630, a buffer tank inlet cooler drain system 640 and a condensate pump 650;

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

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

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

[0070] The pressure-stabilizing gas in the high-temperature water tank 110 and the low-temperature water tank 120 is preferably nitrogen.

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

[0072] The buffer tank 210 is used to store the pressure-stabilizing gas discharged when the gas side pressure in the high-temperature water tank 110 and the low-temperature water tank 120 increases when the power station is running. A spherical tank, a C-type horizontal tank or a vertical tank can be selected according to the heat storage temperature and design pressure of the high-temperature water tank 110 and the low-temperature water tank 120. 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 is also used as a condensate water chamber, which is 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 the high-pressure stabilizing gas that has been compressed and pressurized by the pressure-stabilizing gas compressor 310. The volume of the high-pressure gas storage tank 220 is reduced by increasing the storage pressure of the stabilizing gas, thereby reducing the cost. The high-pressure gas storage tank 220 can use a spherical tank or a C-type horizontal tank, preferably a spherical tank. A high-pressure gas storage tank drain system 610 is arranged at the bottom of the high-pressure gas storage tank 220, and the condensed water in the high-pressure gas storage tank 220 is transported to the buffer tank 210 through a pipeline.

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

[0075] The pressure-stabilizing gas cooler 320 is provided with a pressure-stabilizing gas cooler drain system 620 , and the gas-water separator 330 is provided with a gas-water separator drain system 630 , which transports condensed water to the buffer tank 210 through pipelines.

[0076] The recirculation pipeline 340 is used to ensure the minimum inlet flow rate of the pressure-stabilizing gas compressor 310, and at the same time ensure 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 deliver the discharged pressure stabilizing gas into the buffer tank 210 when the gas side pressure of the high temperature water tank 110 and the low temperature water tank 120 increases; the buffer tank inlet cooler 410 is to cool 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 condense 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 reduce the amount of water, optimize the air intake conditions of the pressure stabilizing gas compressor 310, and reduce 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 gas storage tank 220 back into the high-temperature water tank 110 and the low-temperature water tank 120 after reducing the pressure on the gas side of the high-temperature water tank 110 and the low-temperature water tank 120 through the gas injection and pressure stabilization pressure reducing 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 is basically constant.

[0079] The condensate system 600 collects the condensate from each system in the buffer tank 210 (a separate condensate storage tank may also be provided) and pumps it back to the low-temperature water tank 120 after the condensate is pressurized by the condensate pump 650, so as to ensure the water balance of the whole system and avoid excessive water replenishment, which would cause waste of water resources. The function of the steam trap is to allow only condensate to pass through but not gas.

[0080] The function of the pressure-stabilizing gas replenishment system 700 is to provide the system with pressure-stabilizing gas before the first operation and to replenish the pressure-stabilizing gas loss caused by leakage during the operation of the heat storage system, so as to ensure the stability of the pressure-stabilizing gas volume in the entire system.

[0081] The compressed air energy storage power station generally operates in the following operation mode: the compression energy storage system is started during the off-peak period of electricity consumption, and the compressed air is compressed and stored in the gas storage reservoir by absorbing the excess electricity of the power grid; after the compression energy storage stage, the compression energy storage system is stopped, and the system enters the static stage; the expansion power generation system is started during the peak period of electricity consumption, and the high-pressure air in the gas storage reservoir is released into the expander to generate power; after the expansion power generation stage, the expansion power generation system is stopped, and the system enters the static stage; according to the different peak and valley characteristics of the power grid, some power stations may have multiple peak and valley periods in a day, and their operation mode is basically the same as the above, that is, the compression energy storage system or the expansion power generation system is started according to different peak and valley periods; the present invention takes one peak period and one valley period of electricity consumption per day as an example to illustrate the operation mode of the system:

[0082] An operating method of a nearly constant pressure hot water storage system, characterized in that it comprises the following steps:

[0083] Step 1, compression energy storage stage:

[0084] The low-temperature water tank 120 stores low-temperature water at the highest liquid level, and the high-temperature water tank 110 stores high-temperature water at the lowest liquid level. The gas-side pressures in the high-temperature water tank 110 and the low-temperature water tank 120 are both stable within a set range above the saturation pressure corresponding to the heat storage temperature (considered as saturation pressure + 0.1-0.15MPa range); the high- and low-temperature water tank air discharge and pressure stabilization system 400 is closed, and the pressure in the buffer tank 210 is the same as the gas-side pressures in the low-temperature water tank 120 and the high-temperature water tank 110; the high- and low-temperature water tank air injection and pressure stabilization system 500 is closed, and the high-pressure gas storage tank 220 is filled with high-pressure stabilization gas;

[0085] The low-temperature water circulation pump 142 is started to pump the low-temperature water in the low-temperature water tank 120 into the compression side heat exchanger 152 to heat the low-temperature water into high-temperature water, and then the high-temperature water is sent to the high-temperature water tank 110 for storage; as the low-temperature water circulation pump 142 is running, the liquid level of the low-temperature water in the low-temperature water tank 120 continues to decrease, and the liquid level of the high-temperature water in the high-temperature water tank 110 continues to increase, and 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, and the high-temperature pressure-stabilizing gas is cooled 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 is reduced;

[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, and the high pressure stabilization gas in the high pressure gas storage tank 220 is decompressed by the gas injection and pressure stabilization pressure reducing valve 510 and then injected back into the connecting pipe 130. The flow rate of the reinjected stabilization gas matches the rate of pressure reduction on the gas side, ensuring that the gas side pressures of the high temperature water tank 110 and the low temperature water tank 120 are basically constant (saturation pressure + 0.1-0.15 MPa range is considered);

[0087] After the compression energy storage stage is completed, the low-temperature water circulation pump 142 is stopped, the low-temperature water at the lowest liquid level is stored in the low-temperature water tank 120, and the high-temperature water at the highest liquid level is stored in the high-temperature water tank 110; the high- and low-temperature water tank air release and pressure stabilization 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 air injection and pressure stabilization system 500 is closed, and the pressure of the high-pressure gas storage tank 220 is reduced, but the pressure is still higher than the pressure in the high-temperature water tank 110, the low-temperature water tank 120, and the buffer tank 210;

[0088] Step 2, static stage:

[0089] Closely monitor the gas side pressure of the high temperature water tank 110 and the low temperature water tank 120; the pressure-stabilizing gas in the upper space of the low temperature water tank 120 is cooled by the low temperature water, and the pressure will be slightly reduced; the pressure-stabilizing gas in the upper space of the high temperature water tank 110 is heated by the high temperature water, and the pressure will be slightly increased;

[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, and the high pressure stabilization gas in the high pressure gas storage tank 220 is decompressed by the high pressure stabilization gas through the gas injection and pressure stabilization pressure reducing valve 510 and then injected back into the connecting pipe 130. The flow rate of the reinjected stabilization gas matches the rate of pressure reduction on the gas side, ensuring that the gas side pressures of the high temperature water tank 110 and the low temperature water tank 120 are basically constant (considered in the range of saturation pressure + 0.1-0.15 MPa);

[0092] Step 3, expansion power generation stage:

[0093] 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 pressures in the high-temperature water tank 110 and the low-temperature water tank 120 are stabilized within a set range above the saturation pressure corresponding to the heat storage temperature (considered as saturation pressure + 0.1-0.15MPa range); the high- and low-temperature water tank air release and pressure stabilization system 400 is turned on, and the pressure in the buffer tank 210 is the same as the gas-side pressures in the low-temperature water tank 120 and the high-temperature water tank 110; the high- and low-temperature water tank air injection and pressure stabilization system 500 is turned off, and the high-pressure gas storage tank 220 is filled with high-pressure stabilization gas;

[0094] Start the high-temperature water circulation pump 141, pump the high-temperature water in the high-temperature water tank 110 into the expansion-side heat exchanger 151 to cool it down into low-temperature water, and then send it to the low-temperature water tank 120 for storage; with the operation of the high-temperature water circulation pump 141, the liquid level of the high-temperature water tank 110 continues to decrease, and the liquid level of the low-temperature water tank 120 continues to increase, and 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, and the low-temperature pressure-stabilizing gas is heated and 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-temperature and 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;

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

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

[0097] During operation, the pressure in the high-pressure gas storage tank 220 increases continuously, and the power of the pressure-stabilizing gas compressor 310 is adjusted by frequency conversion to meet the outlet pressure to match the pressure in the high-pressure gas storage tank 220; at the same time, the condensed water of the buffer tank inlet cooler 410, the condensed water of the pressure-stabilizing gas cooler 320, and the condensed water of the gas-water separator 330 enter the buffer tank 210 (or an independently set condensed water storage tank) through their respective steam traps; when the condensed water level in the buffer tank 210 (or an independently set condensed water storage tank) reaches the set value, the condensed water pump 650 is started to pump the condensed water 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 with the highest liquid level is stored in the low-temperature water tank 120, and the high-temperature water with the lowest liquid level is stored in the high-temperature water tank 110; the high- and low-temperature water tank air release and pressure stabilization system 400 is closed, and the pressure in the buffer tank 210 is stable; the high- and low-temperature water tank air injection and pressure stabilization system 500 is closed, and the pressure in the high-pressure gas storage tank 220 increases;

[0099] Step 4, static stage: closely monitor the gas side pressure of the high temperature water tank 110 and the low temperature water tank 120; the pressure-stabilizing gas in the upper space of the low temperature water tank 120 is cooled by the low temperature water, and the pressure will decrease; the pressure-stabilizing gas in the upper space of the high temperature water tank 110 is heated by the high temperature water, and the pressure will increase;

[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, and the high pressure stabilization gas in the high pressure gas storage tank 220 is decompressed by the high pressure stabilization gas through the gas injection and pressure stabilization pressure reducing valve 510 and then injected back into the connecting pipe 130. The flow rate of the reinjected stabilization gas matches the rate of pressure reduction on the gas side, ensuring that the gas side pressures of the high temperature water tank 110 and the low temperature water tank 120 are basically constant (considered in 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, start the pressure-stabilizing gas boosting system 300 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 is basically constant (considered in the range of saturation pressure + 0.1-0.15MPa).

[0103] The first cycle of the heat storage system is completed through the above steps 1-4, and the subsequent cycles of the heat storage system can be carried out by repeating steps 1-4.

[0104] Taking the heat storage medium temperature of 180℃, the operation mode is as follows: 8h of compression energy storage stage, 6h of static stage, 5h of expansion power generation stage, and 5h of static stage, in a single cycle, the theoretical calculation fluctuation of the gas side pressure of the high and low temperature water tanks of the present invention is as follows: Figure 2 As shown in the figure, the theoretical calculation fluctuation of the gas side pressure of the high and low temperature water tanks of the existing high temperature and high pressure hot water thermal storage system is as follows Figure 3 shown by Figure 2 and Figure 3 It can be seen that the gas side pressure fluctuation of the high and low temperature water tanks of the present invention is 0.05MPa, which is only one tenth of the gas side pressure fluctuation of 0.5MPa of the high and low temperature water tanks of the existing high temperature and high pressure hot water thermal storage system. The pressure fluctuation is greatly reduced, which greatly reduces the stress fatigue of the storage tank and increases the service life of the storage tank.

[0105] With a heat storage medium temperature of 180°C and a single storage tank volume of 3500m 3 For example, the comparison table of design parameters of high and low temperature water tanks of the present invention and the existing high temperature and high pressure hot water thermal storage system is as follows:

[0106] project unit Solution of the present invention Existing solutions Tank design temperature ℃ 190 190 Tank capacity <![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] It can be seen from the above table that the weight of a single spherical tank of the present invention is reduced by 100t and the cost is reduced by 2.1 million yuan compared with a single spherical tank of the existing high-temperature and high-pressure heat storage system. Taking the heat storage system of a 300MW compressed air energy storage power station demonstration project as an example, the whole station has a total of 8 3500m 3 The spherical tank of the present invention can save 16.8 million yuan in construction cost, and the economic benefit is obvious.

[0108] In summary, compared with the high-pressure, high-temperature hot water thermal storage system in the prior art, the present invention can effectively reduce the gas-side pressure fluctuation range of high and low temperature water tanks, effectively alleviate the stress fatigue of high and low temperature water tanks, and improve the service life and safety of high and low temperature water tanks, and the pressure fluctuation range is small, which does not belong to the category of fatigue equipment, and can further reduce the design difficulty and measures taken, and reduce the cost of storage tanks; because the pressure fluctuation range of high and low temperature water tanks is small, the present invention can effectively reduce the design pressure of high and low temperature water tanks, thereby reducing the wall thickness of high and low temperature water tanks, reducing the steel consumption per unit volume of high and low temperature water tanks, reducing the cost of heat storage systems, and improving the economic indicators of power stations; because the pressure fluctuation range of high and low temperature water tanks is small, the present 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] Other parts not described belong to the prior art.

Claims

1. A nearly constant pressure hot water heat storage system, comprising a hot water heat storage system (A), wherein the hot water heat 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 via a connecting pipe (130), the high temperature water tank (110) is connected to the low temperature water tank (120) via 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) via a low temperature water circulation pump (142) and at least one stage of compression side heat exchanger (152); Features: It also includes a pressure stabilization system (B), wherein the pressure stabilization system (B) 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) comprises 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-stabilizing gas compressor (310), a pressure-stabilizing gas cooler (320) and a gas-water separator (330).

2. The approximately constant pressure hot water heat storage system according to claim 1, Features: The pressure stabilization system (B) further comprises a high and low temperature water tank air venting and pressure stabilization system (400), wherein the high and low temperature water tank air venting and pressure stabilization system (400) comprises a buffer tank inlet cooler (410), and the connecting pipe (130) is connected to the buffer tank (210) via the buffer tank inlet cooler (410).

3. The approximately constant pressure hot water heat storage system according to claim 2, Features: The pressure stabilization system (B) further comprises a high and low temperature water tank gas injection and pressure stabilization system (500), wherein the high and low temperature water tank gas injection and pressure stabilization system (500) comprises a gas injection and pressure stabilization and pressure reducing valve (510), and the high pressure gas storage tank (220) is connected to the connecting pipe (130) via the gas injection and pressure stabilization and pressure reducing valve (510).

4. The approximately constant pressure hot water heat storage system according to claim 3, Features: The pressure-stabilizing gas boosting system (300) further comprises a recirculation pipeline (340), on which a recirculation valve (341) is arranged; the pressure-stabilizing gas cooler (320) is connected to the gas-water separator (330) and then connected to the buffer tank (210) through the recirculation pipeline (340). 、 The other path is connected to the high-pressure gas storage tank (220).

5. The approximately constant pressure hot water heat storage system according to claim 4, Features: The pressure stabilization system (B) further comprises a condensate water system (600), wherein the condensate water system (600) comprises a high-pressure gas storage tank drain system (610), a pressure stabilization gas cooler drain system (620), a gas-water separator drain system (630), a buffer tank inlet cooler drain system (640) and a condensate water pump (650); The high-pressure gas storage tank drain system (610) comprises a first drain trap (611), and the high-pressure gas storage tank (220) is connected to the buffer tank (210) via the first drain trap (611); the pressure-stabilizing gas cooler drain system (620) comprises a second drain trap (621), and the pressure-stabilizing gas cooler (320) is connected to the buffer tank (210) via the second drain trap (621); the gas-water separator drain system (630) comprises a third drain trap (631), and the gas-water separator (330) is connected to the buffer tank (210) via the third drain trap (631); the buffer tank inlet cooler drain system (640) comprises a fourth drain trap (641), and the buffer tank inlet cooler (410) is connected to the buffer tank (210) via the fourth drain trap (641); The buffer tank (210) is connected to the low-temperature water tank (120) via a condensate pump (650).

6. The approximately constant pressure hot water heat storage system according to claim 5, Features: The pressure stabilization system (B) further comprises a pressure stabilizing gas replenishing system (700), wherein the pressure stabilizing gas replenishing system (700) comprises a pressure stabilizing gas bottle group (710), and the pressure stabilizing gas bottle group (710) is connected to the high-pressure gas storage tank (220).

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

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

9. The method for operating a nearly constant pressure hot water storage system according to claim 6, It is characterized in that The following steps are involved: Step 1, compression energy storage stage: The low-temperature water tank (120) stores low-temperature water at the highest liquid level, and the high-temperature water tank (110) stores high-temperature water at the lowest liquid level. The gas-side pressures in the high-temperature water tank (110) and the low-temperature water tank (120) are both stabilized within a set range above the saturation pressure corresponding to the heat storage temperature; the high- and low-temperature water tank air discharge and pressure stabilization system (400) is closed, and the pressure in the buffer tank (210) is the same as the gas-side pressures in the low-temperature water tank (120) and the high-temperature water tank (110); the high- and low-temperature water tank air injection and pressure stabilization system (500) is closed, and the high-pressure gas storage tank (220) is filled with high-pressure stabilization gas; The low-temperature water circulation pump (142) is started to pump the low-temperature water in the low-temperature water tank (120) into the compression side heat exchanger (152) to heat the low-temperature water to high-temperature water and then send the high-temperature water into the high-temperature water tank (110) for storage; as the low-temperature water circulation pump (142) operates, the liquid level of the low-temperature water in the low-temperature water tank (120) continuously decreases, while the liquid level of the high-temperature water in the high-temperature water tank (110) continuously increases, and the high-temperature pressure-stabilizing gas in the high-temperature water tank (110) is expelled into the low-temperature water tank (120) through the connecting pipe (130), and the high-temperature pressure-stabilizing gas is cooled by the low-temperature water in the low-temperature water tank (120), and the pressure on the gas side of the high-temperature water tank (110) and the low-temperature water tank (120) is reduced; When the pressure drops to the lower limit, the high and low temperature water tank gas injection and pressure stabilization system (500) is opened, and the high pressure stabilization gas in the high pressure gas storage tank (220) is depressurized through the gas injection and pressure stabilization pressure reducing valve (510) and then injected back into the connecting pipe (130), and the flow rate of the injected stabilization gas is matched with the rate of pressure reduction on the gas side, so as to ensure that the gas side pressures of the high temperature water tank (110) and the low temperature water tank (120) are substantially constant; After the compression energy storage stage is completed, the low-temperature water circulation pump (142) is stopped, the low-temperature water at the lowest liquid level is stored in the low-temperature water tank (120), and the high-temperature water at the highest liquid level is stored in the high-temperature water tank (110); the high- and low-temperature water tank air release and pressure stabilization 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 air injection and pressure stabilization system (500) is closed, and the pressure in the high-pressure gas storage tank (220) is reduced, but the pressure is still higher than the pressure in the high-temperature water tank (110), the low-temperature water tank (120), and the buffer tank (210); Step 2, static stage: Closely monitor the gas side pressure of the high temperature water tank (110) and the low temperature water tank (120); the pressure-stabilizing gas in the upper space of the low temperature water tank (120) is cooled by the low temperature water, and the pressure will decrease; the pressure-stabilizing gas in the upper space of the high temperature water tank (110) is heated by the high temperature water, and the pressure will increase; The high-temperature water tank (110) and the low-temperature water tank (120) are pressure-equalized through the connecting pipe (130), and the pressure gradually decreases; When the pressure drops to the lower limit, the high and low temperature water tank gas injection and pressure stabilization system (500) is opened, and the high pressure stabilization gas in the high pressure gas storage tank (220) is depressurized through the gas injection and pressure stabilization pressure reducing valve (510) and then injected back into the connecting pipe (130), and the flow rate of the injected stabilization gas is matched with the rate of pressure reduction on the gas side, so as to ensure that the gas side pressures of the high temperature water tank (110) and the low temperature water tank (120) are substantially 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 pressures in the high-temperature water tank (110) and the low-temperature water tank (120) are stabilized within a set range above the saturation pressure corresponding to the heat storage temperature. The high- and low-temperature water tank air discharge and pressure stabilization system (400) is turned on, and the pressure in the buffer tank (210) is the same as the gas-side pressures in the low-temperature water tank (120) and the high-temperature water tank (110). The high- and low-temperature water tank air injection and pressure stabilization system (500) is turned off, and the high-pressure gas storage tank (220) is filled with high-pressure stabilization gas. The high-temperature water circulation pump (141) is started to pump the high-temperature water in the high-temperature water tank (110) into the expansion-side heat exchanger (151) to cool the high-temperature water into low-temperature water and then send the water into 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), and the gas side pressures of the high-temperature water tank (110) and the low-temperature water tank (120) increase. The pressure-stabilizing gas in the high-temperature water tank (110) and the low-temperature water tank (120) enter the high-temperature and 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 of the buffer tank (210) rises to a set value, the pressure-stabilizing gas boosting system (300) is started; the pressure-stabilizing gas expelled 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 liquid water is separated by the gas-water separator (330) before entering the high-pressure gas storage tank (220) for storage, thereby ensuring that the pressures on the gas sides of the high-temperature water tank (110), the low-temperature water tank (120) and the buffer tank (210) are substantially constant; When the flow rate of the pressure-stabilizing gas expelled into the buffer tank (210) is small, the recirculation pipeline (340) is started, and part of the high-pressure pressure-stabilizing gas at the outlet of the pressure-stabilizing gas compressor (310) is decompressed through the recirculation valve (341) and then returned to the buffer tank (210), thereby ensuring that the intake flow rate of the pressure-stabilizing 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 at the highest liquid level is stored in the low-temperature water tank (120), and the high-temperature water at the lowest liquid level is stored in the high-temperature water tank (110); the high- and low-temperature water tank air release and pressure stabilization 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 air injection and pressure stabilization system (500) is closed, and the pressure of the high-pressure gas storage tank (220) increases; Step 4, static stage: closely monitor the gas side pressure of the high temperature water tank (110) and the low temperature water tank (120); the pressure-stabilizing gas in the upper space of the low temperature water tank (120) is cooled by the low temperature water, and the pressure will decrease; the pressure-stabilizing gas in the upper space of the high temperature water tank (110) is heated by the high temperature water, and the pressure will increase; The high-temperature water tank (110) and the low-temperature water tank (120) are pressure-equalized through the connecting pipe (130), and the pressure gradually decreases; When the pressure drops to the lower limit, the high and low temperature water tank gas injection and pressure stabilization system (500) is opened, and the high pressure stabilization gas in the high pressure gas storage tank (220) is depressurized through the gas injection and pressure stabilization pressure reducing valve (510) and then injected back into the connecting pipe (130), and the flow rate of the injected stabilization gas is matched with the rate of pressure reduction on the gas side, so as to ensure that the gas side pressures of the high temperature water tank (110) and the low temperature water tank (120) are substantially constant; During the static process of step 2 and step 4, 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) is substantially constant; The first cycle of the heat storage system is completed through the above steps 1-4, and the subsequent cycles of the heat storage system can be carried out by repeating steps 1-4.

10. The method for operating the approximately constant pressure hot water storage system according to claim 9, It is characterized in that In step 3, during operation, the pressure in the high-pressure gas storage tank (220) increases continuously, and the output of the pressure-stabilizing gas compressor (310) is adjusted by frequency conversion to meet the outlet pressure to match the pressure in the high-pressure gas storage tank (220); at the same time, 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) enter the buffer tank (210) through their respective steam traps; 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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