Nitrogen constant-temperature and constant-pressure pressurized water energy storage system and pressure fixing method

Abstract

The invention relates to the technical field of compressed air heat storage, in particular to a nitrogen constant-temperature and constant-pressure pressurized water energy storage system and a constant-pressure method. The system comprises a heat storage module, a constant-temperature and constant-pressure module and a pressure relief module. The heat storage module comprises a cold water tank, a heat exchange unit and a hot water tank which are sequentially connected, the cold water tank is connected with a normal-pressure water tank, and the hot water tank is connected with a nitrogen source. The constant-temperature constant-pressure module comprises a first temperature measuring instrument and a first nitrogen heater which are arranged on the cold water tank, and a second temperature measuring instrument and a second nitrogen heater which are arranged on the hot water tank. The pressure relief module comprises a first pressure measuring instrument arranged on the cold water tank, a second pressure measuring instrument arranged on the hot water tank and a water drainage loop connected with the cold water tank and the normal-pressure water tank. The cold water tank and the hot water tank are subjected to temperature monitoring and heating, so that the temperature of nitrogen in the tanks is kept stable, the pressure fluctuation of the system is reduced, the reliability of the system is improved, and the cost of the pressurized water storage tank is effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of compressed air heat storage, and in particular to a nitrogen constant temperature and pressure pressurized water energy storage system and a constant pressure method. Background Art

[0002] The heat storage system has the ability to time-shift energy and respond quickly, which can effectively solve many problems brought by large-scale renewable energy access to the power system. The compressed air heat storage system has the advantages of large capacity, long life, low cost, flexible site selection, and high safety. It has attracted more and more attention from academia and industry and has broad application prospects.

[0003] In a compressed air energy storage system, the air temperature at the compressor outlet can reach over 300°C. In order to effectively utilize this compression heat, a compressed air energy storage system is usually equipped with a heat storage system to store this compression heat. In order to reduce the grade loss of compression heat, high-temperature and high-pressure hot water is generally used as the storage medium to store this compression heat, and the hot water temperature is generally 160°C~190°C. Therefore, in order to prevent the hot water in the storage tank from vaporizing, the storage tank needs to maintain a certain nitrogen pressure.

[0004] However, during the charging and discharging process of the pressurized water energy storage system, the pressurized water is constantly heated or cooled, which will cause the temperature of the nitrogen filled in the system to change due to the temperature of the pressurized water, thereby causing the system pressure to fluctuate. Therefore, in order to prevent the system from overpressure, the existing method is to reserve a certain margin for the design pressure of the storage tank. However, this method will cause the design pressure of the storage tank to increase significantly, significantly increasing the cost of the storage tank. Summary of the invention

[0005] The technical problem to be solved by the embodiments of the present invention is to provide a nitrogen constant temperature and pressure pressurized water energy storage system and a constant pressure method to solve the problem in the prior art that the method of preventing system overpressure by increasing the design pressure of the storage tank will significantly increase the cost of the storage tank.

[0006] The present invention discloses a nitrogen constant temperature and pressure pressurized water energy storage system, comprising: The heat storage module comprises a cold water tank, a heat exchange unit and a hot water tank connected in sequence, wherein the cold water tank is connected to a normal pressure water tank, the normal pressure water tank is pre-filled with a low temperature working medium, and the hot water tank is connected to a nitrogen source; A constant temperature and pressure module, comprising a temperature measuring unit and a heating unit, wherein the temperature measuring unit comprises a first temperature measuring instrument arranged on the cold water tank and a second temperature measuring instrument arranged on the hot water tank, and the heating unit comprises a first nitrogen heater arranged in the cold water tank and a second nitrogen heater arranged in the hot water tank; The pressure relief module includes an overpressure measuring unit and a first-level pressure relief unit. The overpressure measuring unit includes a first pressure measuring instrument arranged on the cold water tank and a second pressure measuring instrument arranged on the hot water tank. The first-level pressure relief unit includes a water relief circuit connecting the cold water tank and the normal pressure water tank.

[0007] Optionally, the pressure relief module further includes a secondary pressure relief unit, and the secondary pressure relief unit includes a first air release valve arranged on the cold water tank and a second air release valve arranged on the hot water tank.

[0008] Optionally, the heat exchange unit includes a common heat exchanger, and a medium flow channel and an air flow channel arranged in the common heat exchanger, the cold water tank is connected to one end of the medium flow channel, and the hot water tank is connected to the other end of the medium flow channel; The common heat exchanger is provided with a first air delivery pipe and a second air delivery pipe, wherein the first air delivery pipe is connected to one end of the air flow channel, and the second air delivery pipe is connected to the other end of the air flow channel.

[0009] Optionally, the heat storage module further includes a pressure pump group, and the hot water tank is connected to the medium flow channel through the pressure pump group; The first air delivery pipeline is provided with a third temperature measuring instrument and a flow measuring instrument, the second air delivery pipeline is provided with a fourth temperature measuring instrument, and the rotation speed of the booster pump group is associated with the measurement values ​​of the third temperature measuring instrument, the flow measuring instrument and the fourth temperature measuring instrument.

[0010] Optionally, a nitrogen filling bypass is connected between the hot water tank and the medium flow channel, and a first solenoid valve is provided on the nitrogen filling bypass; A second solenoid valve is provided on the connecting pipeline between the booster pump group and the hot water tank, and a third solenoid valve is provided on the connecting pipeline between the booster pump group and the medium flow channel.

[0011] Optionally, the heat storage module further includes a working fluid pressure pump, the atmospheric pressure water tank, the working fluid pressure pump and the cold water tank are connected in sequence, a fourth solenoid valve is provided on the connecting pipeline between the working fluid pressure pump and the atmospheric pressure water tank, and a fifth solenoid valve is provided on the connecting pipeline between the working fluid pressure pump and the cold water tank; A sixth solenoid valve is provided on the water drain circuit, and a seventh solenoid valve is provided on the connecting pipeline between the cold water tank and the heat exchange unit.

[0012] Optionally, a first liquid level measuring instrument is provided on the cold water tank, and a second liquid level measuring instrument is provided on the hot water tank, so that the working fluid pressurizing pump controls the amount of water injected into the cold water tank according to the measurement values ​​of the first liquid level measuring instrument and the second liquid level measuring instrument, and the rotation speed of the working fluid pressurizing pump is associated with the measurement value of the first pressure measuring instrument.

[0013] Optionally, an air pressure balance pipeline is connected between the top of the cold water tank and the top of the hot water tank, an eighth solenoid valve is provided on the air pressure balance pipeline, a nitrogen filling interface is provided on the connecting pipeline between the eighth solenoid valve and the hot water tank, and the hot water tank is connected to the nitrogen source through the nitrogen filling interface.

[0014] The present invention also provides a pressure-constant method, using the above-mentioned pressurized water energy storage system, the pressure-constant method comprising: Controlling the nitrogen source to be pressurized and delivered to the hot water tank by an external compression device, and then delivered to the cold water tank through the heat exchange unit until the pressure in the cold water tank and the hot water tank is balanced; Control the first temperature measuring instrument to obtain the temperature value in the cold water tank in real time. If the obtained temperature value is lower than the preset nitrogen temperature, control the first nitrogen heater to start and heat the nitrogen temperature in the cold water tank until the preset nitrogen temperature is reached. At the same time, control the second temperature measuring instrument to obtain the temperature value in the hot water tank in real time. If the obtained temperature value is lower than the preset nitrogen temperature, control the second nitrogen heater to start and heat the nitrogen temperature in the hot water tank until the preset nitrogen temperature is reached. After the nitrogen filling is completed, the atmospheric pressure water tank is controlled to replenish the cold water tank with the initial working fluid; During the system's heat storage or release process, the first pressure measuring instrument is controlled to obtain the pressure value in the cold water tank in real time, and the second pressure measuring instrument is controlled to obtain the pressure value in the hot water tank in real time. If the obtained pressure value exceeds the first preset pressure value, the low-temperature working fluid in the cold water tank is controlled to be discharged into the normal pressure water tank.

[0015] Optionally, the constant pressure method further includes: A second preset pressure value is set whose pressure value is greater than the first preset pressure value. If the obtained pressure value exceeds the second preset pressure value, the nitrogen in the cold water tank and the hot water tank is controlled to be discharged to the outside of the environment.

[0016] Compared with the prior art, the nitrogen constant temperature and pressure pressurized water energy storage system and constant pressure method provided in the embodiments of the present invention have the following beneficial effects: By setting a heat storage module consisting of a cold water tank, a heat exchange unit and a hot water tank, and setting a constant temperature and pressure module, the first temperature measuring instrument can obtain the temperature value in the cold water tank in real time, and the second temperature measuring instrument can obtain the temperature value in the hot water tank in real time, and the nitrogen temperature in the cold water tank is heated by the first nitrogen heater, and the nitrogen temperature in the hot water tank is heated by the second nitrogen heater, so that the nitrogen temperature in the cold water tank and the hot water tank is always kept constant. Therefore, when the system is storing or releasing heat, since the nitrogen temperature remains stable, the pressure fluctuation of the system is only affected by the volume change of the pressurized water working medium between the cold water tank and the hot water tank. Therefore, a pressure relief module is set. When the pressure in the cold water tank and the hot water tank is measured to be overpressure, the low-temperature working medium in the cold water tank only needs to be discharged back to the normal pressure water tank to keep the pressure of the system stable. Then, by maintaining the nitrogen temperature in the cold water tank and the hot water tank, the nitrogen temperature is not affected by the heat charging and discharging of the pressurized water, and the pressure fluctuation of the system is reduced to improve the reliability of the system, without increasing the design pressure of the storage tank, and effectively reducing the cost of the pressurized water storage tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments, in which: Figure 1 A schematic block diagram of the overall structure of a pressurized water energy storage system provided in an embodiment of the present invention.

[0018] The reference numerals in the figures are: 1. Heat storage module; 11. Cold water tank; 111. Seventh solenoid valve; 112. First liquid level measuring instrument; 12. Heat exchange unit; 121. Common heat exchanger; 122. First air delivery pipeline; 123. Second air delivery pipeline; 124. Third temperature measuring instrument; 125. Flow measuring instrument; 126. Fourth temperature measuring instrument; 13. Hot water tank; 131. Nitrogen filling bypass; 132. First solenoid valve; 133. Second liquid level measuring instrument; 14. Normal pressure water tank; 15. Pressure pump group; 151. Second solenoid valve; 152 , the third solenoid valve; 16, the working fluid booster pump; 161, the fourth solenoid valve; 162, the fifth solenoid valve; 2, the constant temperature and pressure module; 21, the first temperature measuring instrument; 22, the second temperature measuring instrument; 23, the first nitrogen heater; 24, the second nitrogen heater; 3, the pressure relief module; 31, the first pressure measuring instrument; 32, the second pressure measuring instrument; 33, the water discharge circuit; 331, the sixth solenoid valve; 34, the first air release valve; 35, the second air release valve; 4, the air pressure balance pipeline; 41, the eighth solenoid valve; 42, the nitrogen filling interface. DETAILED DESCRIPTION

[0019] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. Now, in conjunction with the accompanying drawings, a preferred embodiment of the present invention is described in detail.

[0020] The present invention discloses a nitrogen constant temperature and pressure pressurized water energy storage system, comprising a heat storage module 1, a constant temperature and pressure module 2 and a pressure relief module 3. The heat storage module 1 comprises a cold water tank 11, a heat exchange unit 12 and a hot water tank 13 connected in sequence, the cold water tank 11 is connected to a normal pressure water tank 14, the normal pressure water tank 14 is pre-filled with a low temperature working medium, and the hot water tank 13 is connected to a nitrogen source. The constant temperature and pressure module 2 comprises a temperature measuring unit and a heating unit, the temperature measuring unit comprises a first temperature measuring instrument 21 arranged on the cold water tank 11, and a second temperature measuring instrument 22 arranged on the hot water tank 13, and the heating unit comprises a first nitrogen heater 23 arranged in the cold water tank 11, and a second nitrogen heater 24 arranged in the hot water tank 13. The pressure relief module 3 includes an overpressure measuring unit and a primary pressure relief unit. The overpressure measuring unit includes a first pressure measuring instrument 31 arranged on the cold water tank 11 and a second pressure measuring instrument 32 arranged on the hot water tank 13. The primary pressure relief unit includes a water discharge circuit 33 connecting the cold water tank 11 and the normal pressure water tank 14.

[0021] Through the implementation of the above-mentioned pressurized water energy storage system embodiment, a heat storage module 1 consisting of a cold water tank 11, a heat exchange unit 12 and a hot water tank 13 is provided. When the nitrogen source is pressurized and transported to the hot water tank 13 by an external compression device, the nitrogen is also transported to the cold water tank 11 through the heat exchange unit 12 until the pressure in the cold water tank 11 and the hot water tank 13 is balanced. A constant temperature and pressure module 2 is provided, and the temperature value in the cold water tank 11 is obtained in real time by the first temperature measuring instrument 21, and the temperature value in the hot water tank 13 is obtained in real time by the second temperature measuring instrument 22. If the obtained temperature value is lower than the preset nitrogen temperature, the nitrogen temperature in the cold water tank 11 is heated by the first nitrogen heater 23, and / or the nitrogen temperature in the hot water tank 13 is heated by the second nitrogen heater 24, so that the nitrogen temperature in the cold water tank 11 and the hot water tank 13 are always kept constant. Therefore, when the system is storing or releasing heat, that is, the low-temperature working medium injected into the cold water tank 11 is stored in the hot water tank 13 after heat exchange with the compressed air flowing through the heat exchange unit 12, or the high-temperature working medium stored in the hot water tank 13 is returned to the cold water tank 11 after heat exchange with the compressed air flowing through the heat exchange unit 12, the temperature of the nitrogen in the cold water tank 11 and the hot water tank 13 will not be affected by the heat charging and releasing of the pressurized water working medium, that is, the pressure fluctuation of the system is reduced. Since the nitrogen temperature remains stable, the pressure fluctuation of the system at this time is only affected by the volume change of the pressurized water working medium between the cold water tank 11 and the hot water tank 13. Therefore, a pressure relief module 3 is set. When the pressure in the cold water tank 11 and the hot water tank 13 is measured to exceed the set first preset pressure value, it is only necessary to discharge the low-temperature working medium in the cold water tank 11 back to the normal pressure water tank 14 to keep the pressure of the system stable. Furthermore, by maintaining the temperature of the nitrogen in the cold water tank 11 and the hot water tank 13, the reliability of the system is improved without increasing the design pressure of the storage tank, thereby effectively reducing the cost of the pressurized water storage tank.

[0022] Furthermore, the pressure relief module 3 also includes a secondary pressure relief unit, which includes a first air release valve 34 provided on the cold water tank 11 and a second air release valve 35 provided on the hot water tank 13 .

[0023] Through the implementation of the above-mentioned pressurized water energy storage system embodiment, by using the setting of the secondary pressure relief unit, after controlling the low-temperature working fluid in the cold water tank 11 to be released back to the normal pressure water tank 14, when the pressure in the cold water tank 11 and the hot water tank 13 is still overpressured, the cold water tank 11 and the hot water tank 13 can automatically release nitrogen to the outside of the environment when the pressure is too high through the first air release valve 34 and the second air release valve 35, that is, the cold water tank 11 and the hot water tank 13 provide additional constant pressure protection when the internal pressure exceeds the set second preset pressure value, so as to ensure that the pressure of the system always remains stable. At this time, the second preset pressure value is greater than the first preset pressure value.

[0024] Further, the heat exchange unit 12 includes a common heat exchanger 121, and a medium flow channel and an air flow channel arranged in the common heat exchanger 121, the cold water tank 11 is connected to one end of the medium flow channel, and the hot water tank 13 is connected to the other end of the medium flow channel; The common heat exchanger 121 is provided with a first air delivery pipe 122 and a second air delivery pipe 123 . The first air delivery pipe 122 is connected to one end of the air flow channel, and the second air delivery pipe 123 is connected to the other end of the air flow channel.

[0025] Through the implementation of the above-mentioned pressurized water energy storage system embodiment, the shared heat exchange form can be applied to the multi-stage compression heat storage system, that is, the first air delivery pipeline 122 on the shared heat exchanger 121 is connected to the upper compressor and the lower expander, and the second air delivery pipeline 123 on the shared heat exchanger 121 is connected to the lower compressor and the upper expander. When the compressed air at the outlet of the upper compressor passes through the air flow channel in the shared heat exchanger 121, it exchanges heat with the low-temperature pressurized water working medium passing through the medium flow channel, and then enters the lower compressor to complete the system heat storage. Or when the released air at the outlet of the upper expander passes through the air flow channel in the shared heat exchanger 121, it exchanges heat with the high-temperature pressurized water working medium passing through the medium flow channel, and then enters the lower expander to complete the system heat release. In this way, the shared heat exchange of heat storage and heat release is realized, and then the effective transfer and utilization of thermal energy is realized, the energy conversion efficiency is improved, and the area of ​​the heat exchanger required to be configured in the conventional heat storage system can be greatly reduced.

[0026] Furthermore, the heat storage module 1 further includes a pressure pump group 15, and the hot water tank 13 is connected to the medium flow channel via the pressure pump group 15; A third temperature measuring instrument 124 and a flow measuring instrument 125 are provided on the first air delivery pipeline 122, and a fourth temperature measuring instrument 126 is provided on the second air delivery pipeline 123. The rotation speed of the booster pump group 15 is associated with the measurement values ​​of the third temperature measuring instrument 124, the flow measuring instrument 125 and the fourth temperature measuring instrument 126.

[0027] Through the implementation of the above-mentioned pressurized water energy storage system embodiment, the booster pump group 15 is used, and the booster pump group 15 preferably includes two working fluid pumps, one of which is used for energy storage and the other is used for energy release, so that the two working fluid pumps can quickly respond to pressure changes. That is, when the system is storing heat, only one of the working fluid pumps is started, and the low-temperature pressurized water working fluid injected into the cold water tank 11 is pumped into the common heat exchanger 121 for heat exchange, and the high-temperature pressurized water working fluid after heat exchange is pumped into the hot water tank 13 for storage. Or when the system is releasing heat, only the other working fluid pump is started, and the high-temperature pressurized water working fluid stored in the hot water tank 13 is pumped into the common heat exchanger 121 for heat exchange, and the low-temperature pressurized water working fluid after heat exchange is pumped back to the cold water tank 11. At the same time, during the heat exchange process, the third temperature measuring instrument 124 and the flow measuring instrument 125 are used to monitor the air temperature and air flow through the first air delivery pipeline 122 in real time, and the fourth temperature measuring instrument 126 is used to monitor the air temperature through the second air delivery pipeline 123 in real time. By associating the speed of the booster pump group 15 with the measured values ​​of the third temperature measuring instrument 124, the flow measuring instrument 125 and the fourth temperature measuring instrument 126, that is, when the system stores heat, when the air temperature entering the common heat exchanger 121 is higher and the flow rate is larger, the speed of the booster pump group 15 is controlled to increase. When the system releases heat, when the air temperature entering the common heat exchanger 121 is lower and the flow rate is larger, the speed of the booster pump group 15 is controlled to increase. The heat storage system can automatically adjust the speed of the booster pump group 15 according to the actual heat exchange temperature and flow conditions of the air, thereby realizing adaptive regulation, so as to meet the heat exchange requirements while reducing unnecessary energy consumption and avoiding system instability caused by temperature fluctuations or flow changes.

[0028] Furthermore, a nitrogen filling bypass 131 is connected between the hot water tank 13 and the medium flow channel, and a first solenoid valve 132 is provided on the nitrogen filling bypass 131; A second solenoid valve 151 is provided on the connecting pipeline between the booster pump group 15 and the hot water tank 13 , and a third solenoid valve 152 is provided on the connecting pipeline between the booster pump group 15 and the medium flow channel.

[0029] By implementing the above-mentioned pressurized water energy storage system embodiment and utilizing the setting of the nitrogen filling bypass 131, when the nitrogen is initially filled, the second solenoid valve 151 and the third solenoid valve 152 are closed, and the first solenoid valve 132 is opened, so that when the nitrogen source is pressurized and delivered to the hot water tank 13 by the external compression equipment, the nitrogen is also directly delivered to the cold water tank 11 through the nitrogen filling bypass 131, until the pressure in the cold water tank 11 and the hot water tank 13 is balanced, the nitrogen filling is stopped, and the first solenoid valve 132 is closed. The booster pump group 15 is only used for the delivery of the pressurized water working medium, and nitrogen is prevented from directly entering the booster pump group 15, so as to reduce the problems that the booster pump group 15 may encounter due to the characteristics of nitrogen (such as low viscosity and low density), thereby improving the reliability of the system.

[0030] Furthermore, the heat storage module 1 further includes a working fluid pressure pump 16, the atmospheric pressure water tank 14, the working fluid pressure pump 16 and the cold water tank 11 are connected in sequence, a fourth solenoid valve 161 is provided on the connecting pipeline between the working fluid pressure pump 16 and the atmospheric pressure water tank 14, and a fifth solenoid valve 162 is provided on the connecting pipeline between the working fluid pressure pump 16 and the cold water tank 11; A sixth solenoid valve 331 is provided on the drain circuit 33 , and a seventh solenoid valve 111 is provided on the connecting pipeline between the cold water tank 11 and the heat exchange unit 12 .

[0031] Through the implementation of the above-mentioned pressurized water energy storage system embodiment, after nitrogen is filled to balance the pressure in the cold water tank 11 and the hot water tank 13, the sixth solenoid valve 331 and the seventh solenoid valve 111 are closed, the fourth solenoid valve 161 and the fifth solenoid valve 162 are opened, and the low-temperature pressurized water working medium in the atmospheric pressure water tank 14 is injected into the cold water tank 11 through the working medium pressure pump 16 until the preset injection amount is met, and then the fourth solenoid valve 161 and the fifth solenoid valve 162 are closed, and the seventh solenoid valve 111 is opened to facilitate heat storage and heat exchange. When the pressure in the cold water tank 11 and the hot water tank 13 is measured to be overpressure, the sixth solenoid valve 331 is opened to allow the low-temperature pressurized water working medium in the cold water tank 11 to be discharged back to the atmospheric pressure water tank 14 to achieve pressure relief when the system is overpressured, thereby ensuring the pressure stability of the system.

[0032] Furthermore, a first liquid level measuring instrument 112 is provided on the cold water tank 11, and a second liquid level measuring instrument 133 is provided on the hot water tank 13, so that the working fluid pressure pump 16 controls the amount of water injected into the cold water tank 11 according to the measurement values ​​of the first liquid level measuring instrument 112 and the second liquid level measuring instrument 133, and the rotation speed of the working fluid pressure pump 16 is associated with the measurement value of the first pressure measuring instrument 31.

[0033] Through the implementation of the above-mentioned pressurized water energy storage system embodiment, during the initial water replenishment, the liquid level information of the cold water tank 11 is monitored in real time according to the first liquid level measuring instrument 112, and the water replenishment into the cold water tank 11 is stopped when the liquid level of the cold water tank 11 reaches the preset liquid level. During the heat storage and heat exchange process, considering that a small part of the pressurized water working medium will still be vaporized after heat exchange, the second liquid level measuring instrument 133 can monitor the liquid level information of the hot water tank 13 in real time, and timely control the atmospheric pressure water tank 14 to replenish water to the cold water tank 11, so as to ensure that the high-temperature pressurized water working medium stored in the hot water tank 13 after heat exchange reaches the preset liquid level. In addition, the working medium booster pump 16 is responsible for injecting the low-temperature pressurized water working medium in the atmospheric pressure water tank 14 into the cold water tank 11 to maintain or adjust the pressure in the cold water tank 11. Therefore, when the first pressure measuring instrument 31 detects that the pressure in the cold water tank 11 is lower than the set value, the rotation speed can be increased to increase the injection speed and pressure of the low-temperature pressurized water working medium; conversely, if the pressure in the cold water tank 11 is higher than the set value, the rotation speed can be reduced.

[0034] Furthermore, an air pressure balance pipeline 4 is connected between the top of the cold water tank 11 and the top of the hot water tank 13, an eighth solenoid valve 41 is provided on the air pressure balance pipeline 4, a nitrogen filling interface 42 is provided on the connecting pipeline between the eighth solenoid valve 41 and the hot water tank 13, and the hot water tank 13 is connected to the nitrogen source through the nitrogen filling interface 42.

[0035] Through the implementation of the above-mentioned pressurized water energy storage system embodiment, by using the setting of the air pressure balance pipeline 4, the system opens the eighth solenoid valve 41 during the process of heat storage, heat exchange or heat release, so that the pressure between the cold water tank 11 and the hot water tank 13 can be balanced with each other, that is, when the pressure of one tank changes, the pressure of the other tank will also change accordingly, thereby maintaining the pressure stability of the entire system and further reducing the pressure fluctuation of the system. When nitrogen is initially injected, the eighth solenoid valve 41, the second solenoid valve 151 and the third solenoid valve 152 are closed, and the first solenoid valve 132 is opened, so that the nitrogen source is pressurized and transported to the hot water tank 13 by the external compression equipment, and directly transported into the cold water tank 11 through the nitrogen filling bypass 131, until the pressure in the cold water tank 11 and the hot water tank 13 is balanced, then the nitrogen filling is stopped, and the nitrogen source and the first solenoid valve 132 are closed.

[0036] The present invention also provides a pressure setting method, using the above-mentioned pressurized water energy storage system, the pressure setting method comprises: The nitrogen source is controlled to be pressurized and delivered to the hot water tank 13 by an external compression device, and then delivered to the cold water tank 11 through the heat exchange unit 12 until the pressure in the cold water tank 11 and the hot water tank 13 is balanced; Control the first temperature measuring instrument 21 to obtain the temperature value in the cold water tank 11 in real time. If the obtained temperature value is lower than the preset nitrogen temperature, control the first nitrogen heater 23 to start and heat the nitrogen temperature in the cold water tank 11 until the preset nitrogen temperature is reached. At the same time, control the second temperature measuring instrument 22 to obtain the temperature value in the hot water tank 13 in real time. If the obtained temperature value is lower than the preset nitrogen temperature, control the second nitrogen heater 24 to start and heat the nitrogen temperature in the hot water tank 13 until the preset nitrogen temperature is reached; After the nitrogen filling is completed, the atmospheric pressure water tank 14 is controlled to replenish the cold water tank 11 with the initial working fluid; During the system's heat storage or heat release process, the first pressure measuring instrument 31 is controlled to obtain the pressure value in the cold water tank 11 in real time, and the second pressure measuring instrument 32 is controlled to obtain the pressure value in the hot water tank 13 in real time. If the obtained pressure value exceeds the first preset pressure value, the low-temperature working fluid in the cold water tank 11 is controlled to be discharged into the normal pressure water tank 14.

[0037] Furthermore, the constant pressure method also includes: A second preset pressure value is set whose pressure value is greater than the first preset pressure value. If the obtained pressure value exceeds the second preset pressure value, the nitrogen in the cold water tank 11 and the hot water tank 13 is controlled to be released to the outside of the environment.

[0038] By implementing the above-mentioned constant pressure method embodiment and using the above-mentioned pressurized water energy storage system, the working process of the present invention is as follows: S1. Initial working fluid replenishment: The second solenoid valve 151, the third solenoid valve 152, the fourth solenoid valve 161, the fifth solenoid valve 162, the sixth solenoid valve 331, and the eighth solenoid valve 41 are closed, the first solenoid valve 132 and the seventh solenoid valve 111 are opened, and nitrogen enters the system through the nitrogen filling interface 42, and is pressurized by the external compressor and sequentially transported to the hot water tank 13 and the cold water tank 11. After the nitrogen filling is completed, the seventh solenoid valve 111 is closed, the fourth solenoid valve 161 and the fifth solenoid valve 162 are opened, and the low-temperature pressurized water working medium in the atmospheric water tank 14 is pressurized and transported to the cold water tank 11 by the working medium pressure pump 16. After the water replenishment is completed, the initial working medium replenishment process of the system ends.

[0039] S2, system heat storage: The first solenoid valve 132, the fourth solenoid valve 161, and the fifth solenoid valve 162 are closed, and the second solenoid valve 151, the third solenoid valve 152, the seventh solenoid valve 111, and the eighth solenoid valve 41 are opened, and the low-temperature pressurized water medium flows out of the cold water tank 11, is heated by the compressed air passing through the common heat exchanger 121, and enters the hot water tank 13 after being pressurized by the booster pump group 15. Since the nitrogen temperature is kept stable by the heating unit, the pressure fluctuation is only caused by the change in the volume of the pressurized water.

[0040] S3, system heat release: The high-temperature pressurized water flows out of the hot water tank 13, is pressurized by the booster pump group 15, and enters the common heat exchanger 121. It is cooled by the compressed air passing through the common heat exchanger 121 and enters the cold water tank 11. Since the nitrogen temperature is kept stable by the heating unit, the pressure fluctuation is only caused by the volume change of the pressurized water.

[0041] S4, overpressure relief: When the pressure in the cold water tank 11 or the hot water tank 13 exceeds the first preset pressure value, the sixth solenoid valve 331 opens, and the low-temperature pressurized water working medium in the cold water tank 11 is discharged into the normal pressure water tank 14 .

[0042] When the pressure in the cold water tank 11 or the hot water tank 13 exceeds the second preset pressure value, the first air release valve 34 or the second air release valve 35 opens to release the nitrogen in the cold water tank 11 or the hot water tank 13 into the atmosphere to protect the safety of the cold water tank 11 and the hot water tank 13 equipment.

[0043] As described above, the constant pressure method of the present invention is suitable for nitrogen constant pressure in a pressurized water energy storage system. It can stably maintain the nitrogen temperature in the pressurized water energy storage system and keep the nitrogen expansion degree unaffected by the system operation, thereby reducing the pressure fluctuation in the cold water tank 11 or the hot water tank 13.

[0044] It should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. For those skilled in the art, the technical solutions described in the above embodiments can be modified, or some of the technical features therein can be replaced by equivalents; and all these modifications and replacements should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A nitrogen constant temperature and pressure pressurized water energy storage system, characterized in that: The pressurized water energy storage system comprises: The heat storage module comprises a cold water tank, a heat exchange unit and a hot water tank connected in sequence, wherein the cold water tank is connected to a normal pressure water tank, the normal pressure water tank is pre-filled with a low temperature working medium, and the hot water tank is connected to a nitrogen source; A constant temperature and pressure module, comprising a temperature measuring unit and a heating unit, wherein the temperature measuring unit comprises a first temperature measuring instrument arranged on the cold water tank and a second temperature measuring instrument arranged on the hot water tank, and the heating unit comprises a first nitrogen heater arranged in the cold water tank and a second nitrogen heater arranged in the hot water tank; The pressure relief module includes an overpressure measuring unit and a first-level pressure relief unit. The overpressure measuring unit includes a first pressure measuring instrument arranged on the cold water tank and a second pressure measuring instrument arranged on the hot water tank. The first-level pressure relief unit includes a water relief circuit connecting the cold water tank and the normal pressure water tank.

2. The nitrogen constant temperature and pressure pressurized water energy storage system according to claim 1 is characterized in that: The pressure relief module further includes a secondary pressure relief unit, which includes a first air release valve arranged on the cold water tank and a second air release valve arranged on the hot water tank.

3. The nitrogen constant temperature and pressure pressurized water energy storage system according to claim 1 is characterized in that: The heat exchange unit includes a common heat exchanger, and a medium flow channel and an air flow channel arranged in the common heat exchanger, the cold water tank is connected to one end of the medium flow channel, and the hot water tank is connected to the other end of the medium flow channel; The common heat exchanger is provided with a first air delivery pipe and a second air delivery pipe, wherein the first air delivery pipe is connected to one end of the air flow channel, and the second air delivery pipe is connected to the other end of the air flow channel.

4. The nitrogen constant temperature and pressure pressurized water energy storage system according to claim 3 is characterized in that: The heat storage module further includes a pressure pump group, and the hot water tank is connected to the medium flow channel through the pressure pump group; The first air delivery pipeline is provided with a third temperature measuring instrument and a flow measuring instrument, the second air delivery pipeline is provided with a fourth temperature measuring instrument, and the rotation speed of the booster pump group is associated with the measurement values ​​of the third temperature measuring instrument, the flow measuring instrument and the fourth temperature measuring instrument.

5. The nitrogen constant temperature and pressure pressurized water energy storage system according to claim 4 is characterized in that: A nitrogen filling bypass is connected between the hot water tank and the medium flow channel, and a first solenoid valve is provided on the nitrogen filling bypass; A second solenoid valve is provided on the connecting pipeline between the booster pump group and the hot water tank, and a third solenoid valve is provided on the connecting pipeline between the booster pump group and the medium flow channel.

6. The nitrogen constant temperature and pressure pressurized water energy storage system according to claim 1 is characterized in that: The heat storage module further includes a working fluid pressure pump, the atmospheric pressure water tank, the working fluid pressure pump and the cold water tank are connected in sequence, a fourth solenoid valve is provided on the connecting pipeline between the working fluid pressure pump and the atmospheric pressure water tank, and a fifth solenoid valve is provided on the connecting pipeline between the working fluid pressure pump and the cold water tank; A sixth solenoid valve is provided on the water drain circuit, and a seventh solenoid valve is provided on the connecting pipeline between the cold water tank and the heat exchange unit.

7. The nitrogen constant temperature and pressure pressurized water energy storage system according to claim 6 is characterized in that: A first liquid level measuring instrument is provided on the cold water tank, and a second liquid level measuring instrument is provided on the hot water tank, so that the working fluid pressurizing pump controls the amount of water injected into the cold water tank according to the measurement values ​​of the first liquid level measuring instrument and the second liquid level measuring instrument, and the rotation speed of the working fluid pressurizing pump is associated with the measurement value of the first pressure measuring instrument.

8. The nitrogen constant temperature and pressure pressurized water energy storage system according to claim 1 is characterized in that: An air pressure balance pipeline is connected between the top of the cold water tank and the top of the hot water tank, an eighth solenoid valve is arranged on the air pressure balance pipeline, a nitrogen filling interface is arranged on the connecting pipeline between the eighth solenoid valve and the hot water tank, and the hot water tank is connected to the nitrogen source through the nitrogen filling interface.

9. A constant pressure method, characterized in that: The nitrogen constant temperature and pressure pressurized water energy storage system according to any one of claims 1 to 8 is adopted, and the constant pressure method comprises: Controlling the nitrogen source to be pressurized and delivered to the hot water tank by an external compression device, and then delivered to the cold water tank through the heat exchange unit until the pressure in the cold water tank and the hot water tank is balanced; Control the first temperature measuring instrument to obtain the temperature value in the cold water tank in real time. If the obtained temperature value is lower than the preset nitrogen temperature, control the first nitrogen heater to start and heat the nitrogen temperature in the cold water tank until the preset nitrogen temperature is reached. At the same time, control the second temperature measuring instrument to obtain the temperature value in the hot water tank in real time. If the obtained temperature value is lower than the preset nitrogen temperature, control the second nitrogen heater to start and heat the nitrogen temperature in the hot water tank until the preset nitrogen temperature is reached. After the nitrogen filling is completed, the atmospheric pressure water tank is controlled to replenish the cold water tank with the initial working fluid; During the system's heat storage or release process, the first pressure measuring instrument is controlled to obtain the pressure value in the cold water tank in real time, and the second pressure measuring instrument is controlled to obtain the pressure value in the hot water tank in real time. If the obtained pressure value exceeds the first preset pressure value, the low-temperature working fluid in the cold water tank is controlled to be discharged into the normal pressure water tank.

10. The constant pressure method according to claim 9, characterized in that: The constant pressure method further comprises: A second preset pressure value is set whose pressure value is greater than the first preset pressure value. If the obtained pressure value exceeds the second preset pressure value, the nitrogen in the cold water tank and the hot water tank is controlled to be discharged to the outside of the environment.

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