Energy recovery type supercritical compression carbon dioxide energy storage system and constant pressure energy release method

Abstract

The application provides an energy recovery type supercritical compression carbon dioxide energy storage system, which comprises a low-pressure gas storage tank, a high-pressure gas storage tank, a compressor, a cooler I, a cooler II, a low-grade heat recovery tank, a heat storage tank, a cold storage tank, a reheater and an expander; the gas outlet of the low-pressure gas storage tank is communicated with the gas inlet of the compressor; the gas outlet of the compressor is communicated with the gas inlet of the cooler I; the gas outlet of the cooler I is communicated with the gas inlet of the high-pressure gas storage tank; the gas outlet of the high-pressure gas storage tank is communicated with the gas inlet of the reheater; the gas outlet of the reheater is communicated with the gas inlet of the expander; the gas outlet of the expander is communicated with the gas inlet of the cooler II; and the gas outlet of the cooler II is communicated with the gas inlet of the low-pressure gas storage tank. Through the system, the low-grade energy in the cycle process can be recycled and utilized, and the cycle efficiency of the compressed carbon dioxide energy storage system is improved.

Description

Technical Field

[0001] This invention relates to a carbon dioxide energy storage system, and more particularly to an energy recovery type supercritical compressed carbon dioxide energy storage system and a constant pressure energy release method. Background Technology

[0002] Compressed carbon dioxide (CCCO) energy storage technology is a novel physical energy storage technology with advantages such as high energy density, long service life, and compact system equipment, showing promising development and application prospects. However, during the discharge process of a CCCO energy storage system, the pressure inside the high-pressure gas tank gradually decreases as high-pressure gas is continuously discharged, causing the operating conditions of key components such as the turbine to change constantly, and even leading to system instability and difficulty in improving cycle efficiency. Furthermore, the working fluid at the expander outlet and the cold storage tank inlet carries a large amount of low-grade heat, which is difficult to utilize directly by using natural cooling water or air cooling, significantly reducing system efficiency.

[0003] Therefore, in order to solve the above-mentioned technical problems, it is urgent to propose a new technical approach. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide an energy recovery type supercritical compressed carbon dioxide energy storage system and a constant pressure energy release method. On the one hand, it can solve the problem that the pressure in the high-pressure gas storage tank decreases as the gas is discharged during the cyclic discharge process of supercritical compressed carbon dioxide energy storage. On the other hand, it can realize the recovery and utilization of low-grade energy during the cycle.

[0005] The present invention provides an energy recovery type supercritical compressed carbon dioxide energy storage system, comprising a low-pressure gas storage tank, a high-pressure gas storage tank, a compressor, a cooler I, a cooler II, a low-grade heat recovery tank, a heat storage tank, a cold storage tank, a reheater, and an expander;

[0006] The outlet of the low-pressure gas storage tank is connected to the inlet of the compressor, and the low-pressure gas storage tank is used to store low-pressure carbon dioxide.

[0007] The compressor's outlet is connected to the cooler I's inlet, and the compressor is used to compress low-pressure carbon dioxide into high-pressure carbon dioxide.

[0008] The outlet of the cooler I is connected to the inlet of the high-pressure gas storage tank through an airflow channel, and the airflow channel between the outlet of the cooler I and the inlet of the high-pressure gas storage tank passes through the low-grade heat recovery tank. The cooler I is used to cool down the compressed carbon dioxide and absorb the compression heat generated by the compressor.

[0009] The outlet I of the low-grade heat recovery tank is connected to the inlet of the high-pressure gas storage tank through a liquid flow channel; the outlet I of the low-grade heat recovery tank is connected to the outlet of the high-pressure gas storage tank through a liquid flow channel; the low-grade heat recovery tank is used to absorb the low-grade heat carried by the carbon dioxide output by the cooler I, and to provide low-grade heat to the high-pressure gas storage tank through a heat exchange medium, heating the carbon dioxide in the high-pressure gas storage tank to a supercritical state, and keeping the pressure of the carbon dioxide in the high-pressure gas storage tank constant during the gas release process;

[0010] The outlet of the high-pressure gas storage tank is connected to the inlet of the reheater, and the high-pressure gas storage tank is used to store high-pressure carbon dioxide.

[0011] The outlet of the reheater is connected to the inlet of the expander. The reheater is used to heat supercritical carbon dioxide, so that the carbon dioxide in the reheater becomes a high temperature and high pressure state.

[0012] The outlet of the expander is connected to the inlet of the cooler II. The expander is used to expand carbon dioxide at constant pressure to do work.

[0013] The outlet of the cooler II is connected to the inlet of the low-pressure gas storage tank, and the cooler II is used to cool and lower the temperature of the expanded carbon dioxide.

[0014] The inlet of the cooler II is connected to the outlet II of the low-grade heat recovery tank through a liquid flow channel. The outlet of the cooler II is connected to the inlet II of the low-grade heat recovery tank through a liquid flow channel. The inlet and outlet of the cooler II are connected through a liquid flow channel. The cooler II is also used to absorb the low-grade heat carried by carbon dioxide in the cooler II.

[0015] The inlet of the heat storage tank is connected to the outlet of the cooler I through a liquid flow channel, and the outlet of the heat storage tank is connected to the inlet of the reheater through a liquid flow channel; the heat storage tank stores high-grade heat generated by the compressor through a heat exchange medium, and provides high-grade heat to the reheater through the heat exchange medium;

[0016] The inlet of the cold storage tank is connected to the outlet of the reheater through a liquid flow channel, and the connected liquid flow channel passes through the low-grade heat recovery tank. The outlet of the cold storage tank is connected to the inlet of the cooler I through a liquid flow channel. The cold storage tank is used to store the heat exchange medium cooled in the reheater and to provide the cooled heat exchange medium to the cooler I. The low-grade heat recovery tank is also used to absorb the low-grade heat in the heat exchange medium cooled in the reheater.

[0017] Furthermore, the liquid outlet of the high-pressure gas storage tank is located on the side of the air inlet of the high-pressure gas storage tank; the liquid inlet of the high-pressure gas storage tank is located on the side of the air outlet of the high-pressure gas storage tank.

[0018] Furthermore, the inlet and outlet of the high-pressure gas storage tank are connected by a spiral liquid flow channel; the spiral liquid flow channel is used to enable the heat exchange medium in the spiral liquid flow channel to achieve countercurrent heat exchange with the carbon dioxide in the high-pressure gas storage tank.

[0019] Furthermore, the high-pressure gas storage tank is equipped with valves at its air inlet, air outlet, liquid inlet, and liquid outlet.

[0020] Furthermore, it also includes temperature sensors and pressure sensors;

[0021] The temperature sensor is installed inside the high-pressure gas storage tank and is used to measure the temperature inside the high-pressure gas storage tank and the temperature of the heat exchange medium in the spiral liquid flow channel.

[0022] The pressure sensor is installed inside the high-pressure gas storage tank and is used to measure the pressure inside the high-pressure gas storage tank.

[0023] Furthermore, it also includes the pump body, control box, and display screen;

[0024] The pump body's output port is connected to the liquid inlet of the high-pressure gas storage tank and the liquid inlet of the cooler II. The pump body is used to draw in the heat exchange medium in the low-grade heat recovery tank and input the heat exchange medium into the spiral liquid flow channel or the liquid flow channel of the cooler II.

[0025] The input terminal of the control box is connected to the output terminals of the temperature sensor and the pressure sensor. The output terminal of the control box is connected to the valve at the inlet of the high-pressure gas storage tank, the valve at the outlet of the high-pressure gas storage tank, and the output terminal of the pump body. The control box is used to control the pump body to extract the heat exchange medium from the low-grade heat recovery tank according to the temperature and pressure inside the high-pressure gas storage tank and the temperature of the heat exchange medium, and to control the flow rate of the heat exchange medium by controlling the opening of the valve at the inlet of the high-pressure gas storage tank.

[0026] The input terminal of the display screen is connected to the output terminals of the temperature sensor and the pressure sensor, and is used to display the temperature in the high-pressure gas storage tank, the temperature of the heat exchange medium in the spiral liquid flow channel, and the pressure in the high-pressure gas storage tank.

[0027] Furthermore, both the high-pressure gas storage tank and the low-pressure gas storage tank are provided with a drain port at their bottom; both the drain port of the high-pressure gas storage tank and the drain port of the low-pressure gas storage tank are equipped with valves, and the drain ports of the high-pressure gas storage tank and the low-pressure gas storage tank are used to discharge impurities from the tank.

[0028] Accordingly, the present invention also provides a constant-pressure energy release method based on the above-mentioned energy recovery type supercritical compressed carbon dioxide energy storage system, comprising the following steps:

[0029] S1. The low-pressure gas storage tank inputs low-pressure carbon dioxide into the compressor and compresses the low-pressure carbon dioxide to a high-temperature and high-pressure state;

[0030] S2. The compressor inputs high-temperature and high-pressure carbon dioxide into cooler I, and then from cooler I into the high-pressure storage tank; a low-grade heat recovery tank is used to heat the carbon dioxide in the high-pressure storage tank, so that the temperature of the carbon dioxide in the high-pressure storage tank is maintained within [AB, AC].

[0031] Where A represents the pseudo-critical point temperature of carbon dioxide in the high-pressure gas storage tank, [AB,AC] represents the temperature near the pseudo-critical point of carbon dioxide, AC represents the upper limit of the temperature near the pseudo-critical point of carbon dioxide, and AB represents the lower limit of the temperature near the pseudo-critical point of carbon dioxide.

[0032] S3. Open the valve at the outlet of the high-pressure gas storage tank to input the carbon dioxide in the high-pressure gas storage tank into the reheater. At the same time, the control box controls the flow rate Q of the heat exchange medium input spiral liquid flow channel of the low-grade heat recovery tank so that the real-time pressure of carbon dioxide in the high-pressure gas storage tank is equal to the preset pressure.

[0033] S4. The reheater receives carbon dioxide at a constant pressure and heats it, then inputs the heated carbon dioxide into the expander for constant-pressure energy release.

[0034] Furthermore, in step S3, the flow rate Q is calculated using the following formula:

[0035]

[0036] Where M represents the mass of carbon dioxide in the high-pressure gas storage tank, h d h represents the specific enthalpy of carbon dioxide in a high-pressure gas storage tank at a set pressure. r c represents the specific enthalpy of carbon dioxide in a high-pressure gas storage tank under real-time pressure. l t1 and t2 represent the specific heat capacity of the heat exchange medium, respectively, the start time and the time to heat carbon dioxide in the temperature range [AB, AC] of the low-grade heat recovery tank to the specified pressure, and dT represents the temperature change of the heat exchange medium in the spiral liquid flow channel in the high-pressure gas storage tank.

[0037] Furthermore, h d and h r Calculated using the following formula:

[0038] h r =refpropm('h', 'T', T) g，r,'P′,P r (CO2)

[0039] h d =refpropm('h', 'P', P) d ,'D′,ρ,'CO2')

[0040] Where refpropm represents a function, P d P represents the preset pressure of carbon dioxide in the high-pressure gas storage tank. r T represents the actual pressure of carbon dioxide in the high-pressure gas storage tank. g，r ρ represents the real-time temperature of carbon dioxide in the high-pressure storage tank, ρ represents the density of carbon dioxide in the high-pressure storage tank, 'h', 'T', 'P' and 'D' represent enthalpy, temperature, pressure and density respectively, and 'CO2' represents the working medium of carbon dioxide.

[0041] The beneficial effects of this invention are as follows: This invention utilizes the characteristic that the density of carbon dioxide changes drastically with temperature near the quasi-critical point to recover low-grade heat from the compressed carbon dioxide energy storage system and use it to heat the high-pressure gas storage tank, thereby controlling the temperature and pressure of carbon dioxide in the high-pressure gas storage tank near the quasi-critical point. When the pressure inside the tank decreases, only a slight increase in heating temperature is needed to quickly compensate for the decrease in pressure, thus achieving a constant-pressure discharge process in the energy storage system. At the same time, the low-grade energy in the system can be used for the heating process of the high-pressure gas storage tank, thereby improving the energy utilization rate of the system. Attached Figure Description

[0042] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0043] Figure 1 This is a schematic diagram of the system structure of the present invention;

[0044] Figure 2 This is a schematic diagram of the high-pressure gas storage tank part of the present invention;

[0045] Figure 3 It has the physical properties of supercritical carbon dioxide;

[0046] Figure 4 This is a flowchart of the present invention;

[0047] Attached reference numerals: 1-Low-pressure gas storage tank; 2-Compressor; 3-Cooler I; 4-Low-grade heat recovery tank; 5-High-pressure gas storage tank; 6-Reheater; 7-Expander; 8-Cooler II; 9-Heat storage tank; 10-Cold storage tank; 11-High-pressure gas storage tank body; 12-High-pressure gas storage tank inlet; 13-High-pressure gas storage tank outlet; 14-High-pressure gas storage tank drain outlet; 15-Support base; 16-High-pressure gas storage tank liquid inlet; 17-High-pressure gas storage tank liquid outlet; 18-Spiral liquid flow channel; 19-Temperature sensor; 20-Pressure sensor; 21-Control box; 22-Display screen. Detailed Implementation

[0048] The present invention will be further described below with reference to the accompanying drawings:

[0049] This invention provides an energy recovery type supercritical compressed carbon dioxide energy storage system, such as... Figure 1 As shown, it includes a low-pressure gas storage tank 1, a high-pressure gas storage tank 5, a compressor 2, a cooler I 3, a cooler II 8, a low-grade heat recovery tank 4, a heat storage tank 9, a cold storage tank 10, a reheater 6, and an expander 7.

[0050] Figure 1 The thick solid line represents the carbon dioxide channel, the thin solid line represents the liquid flow channel, the broken line represents the heat exchange, and the thin dashed line represents the flow channel of the heat exchange medium inside the low-grade heat recovery tank 4.

[0051] The outlet of the low-pressure gas storage tank 1 is connected to the inlet of the compressor, and the low-pressure gas storage tank 1 is used to store low-pressure carbon dioxide.

[0052] The outlet of the compressor 2 is connected to the inlet of the cooler I 3. The compressor 2 is used to compress low-pressure carbon dioxide into high-pressure carbon dioxide. The compressor 2 uses surplus power from the power grid or electricity generated by the discharge of renewable energy to compress carbon dioxide. Essentially, it stores electrical energy through pressure potential energy and heat energy. The pressure potential energy and heat energy are stored in the high-pressure gas storage tank 5 and the heat storage tank 9 respectively with the output of the compressor.

[0053] The outlet of the cooler I3 is connected to the inlet of the high-pressure gas storage tank 5 through an airflow channel, and the airflow channel between the outlet of the cooler I3 and the inlet of the high-pressure gas storage tank 5 passes through the low-grade heat recovery tank 4. The cooler I3 is used to cool down the compressed carbon dioxide and absorb the compression heat generated by the compressor 2.

[0054] The outlet I of the low-grade heat recovery tank 4 is connected to the inlet of the high-pressure gas storage tank 5 through a liquid flow channel; the outlet I of the low-grade heat recovery tank 4 is connected to the outlet of the high-pressure gas storage tank 5 through a liquid flow channel; it is used to absorb the low-grade heat carried by the carbon dioxide output by the cooler I 3, and to provide low-grade heat to the high-pressure gas storage tank 5 through a heat exchange medium, heating the carbon dioxide in the high-pressure gas storage tank 5 to a supercritical state, and keeping the pressure of the carbon dioxide in the high-pressure gas storage tank 5 constant during the gas release process; the low-grade heat recovery technology is existing technology and will not be described in detail here;

[0055] The outlet of the high-pressure gas storage tank 5 is connected to the inlet of the reheater 6, and the high-pressure gas storage tank 5 is used to store high-pressure carbon dioxide.

[0056] The outlet of the reheater 6 is connected to the inlet of the expander 7. The reheater 6 is used to heat supercritical carbon dioxide, so that the carbon dioxide in the reheater 6 becomes a high temperature and high pressure state.

[0057] The outlet of the expander 7 is connected to the inlet of the cooler II 8. The expander 7 is used to expand carbon dioxide at constant pressure to do work.

[0058] The outlet of the cooler II 8 is connected to the inlet of the low-pressure gas storage tank 1. The cooler II 8 is used to cool and lower the temperature of the expanded carbon dioxide.

[0059] The inlet of the cooler II 8 is connected to the outlet II of the low-grade heat recovery tank 4 through a liquid flow channel. The outlet of the cooler II 8 is connected to the inlet II of the low-grade heat recovery tank 4 through a liquid flow channel. The inlet and outlet of the cooler II 8 are connected through a liquid flow channel. The low-grade heat recovery tank 4 is also used to absorb the low-grade heat carried by carbon dioxide in the cooler II 8.

[0060] The inlet of the heat storage tank 9 is connected to the outlet of the cooler I3 through a liquid flow channel, and the outlet of the heat storage tank 9 is connected to the inlet of the reheater 6 through a liquid flow channel; the heat storage tank 9 stores the high-grade heat generated by the compressor 2 through a heat exchange medium, and provides high-grade heat to the reheater 6 through the heat exchange medium.

[0061] The inlet of the cold storage tank 10 is connected to the outlet of the reheater 6 through a liquid flow channel, and the connected liquid flow channel passes through the low-grade heat recovery tank 4. The outlet of the cold storage tank 10 is connected to the inlet of the cooler I3 through a liquid flow channel. The cold storage tank 10 is used to store the heat exchange medium cooled in the reheater 6 and to provide the cooled heat exchange medium to the cooler I3. The low-grade heat recovery tank 4 is also used to absorb the low-grade heat in the heat exchange medium cooled in the reheater 6.

[0062] The cooler I3 is provided with an airflow channel, which connects the air inlet and outlet of the cooler I3 for the flow of carbon dioxide. The cooler I3 also has a liquid flow channel, which connects the liquid inlet and outlet for the flow of heat exchange medium. The remaining structure of the cooler I3 adopts existing structures and will not be described in detail here. The cooler I3 contains a heat exchange medium. When carbon dioxide carrying compression heat enters the airflow channel of the cooler I3, it exchanges heat with the heat exchange medium in the cooler I3. The heat exchange medium in the cooler I3 then exchanges heat with the heat exchange medium in the liquid flow channel, causing the compression heat generated by the compressor to flow to the heat storage tank 9 along with the heat exchange medium in the liquid flow channel.

[0063] The reheater 6 is provided with an airflow channel, which connects the air inlet and outlet of the reheater 6. The reheater 6 is also provided with a liquid flow channel, which connects the liquid inlet and outlet of the reheater 6. The reheater 6 is filled with heat exchange medium. When the heat exchange medium in the heat storage tank 9 flows into the reheater through the liquid flow channel, heat exchange occurs between the heat exchange medium in the liquid flow channel and the heat exchange medium in the reheater 6. The heat exchange medium in the reheater 6 then exchanges heat with the carbon dioxide in the airflow channel, thereby heating the carbon dioxide. The heat exchange medium that has absorbed heat in the liquid flow channel passes through the low-grade heat recovery tank and enters the cold storage tank 10.

[0064] The cooler II 8 is provided with an airflow channel, which connects the air inlet and outlet of the cooler II 8. The cooler II 8 is also provided with a liquid flow channel, which connects the liquid inlet and outlet of the cooler II 8. The cooler II 8 contains a heat exchange medium. The remaining structure of the cooler II 8 adopts existing structures and will not be described in detail here. When the expanded carbon dioxide enters the airflow channel of the cooler II 8, the expanded carbon dioxide exchanges heat with the heat exchange medium in the cooler II 8. The heat exchange medium in the cooler II 8 then exchanges heat with the heat exchange medium in the liquid flow channel, thereby enabling the low-grade heat recovery tank to absorb the low-grade heat of the expanded carbon dioxide.

[0065] The low-grade heat in the low-grade heat recovery tank 4 has three sources. First, when the cooler I3 inputs carbon dioxide into the high-pressure gas storage tank 5, the low-grade heat carried in the carbon dioxide is absorbed by the low-grade heat recovery tank 4 as the airflow passage passes through it. Second, when the reheater 6 inputs heat exchange medium into the cold storage tank 10, the heat exchange medium output from the reheater 6 through the liquid flow passage carries low-grade heat, and this liquid flow passage passes through the low-grade heat recovery tank 4, where the low-grade heat is absorbed by the liquid flow passage. The flow channel passes through the low-grade heat recovery tank 4. The heat exchange medium in the liquid flow channel exchanges heat with the heat exchange medium in the low-grade heat recovery tank 4. At this time, the low-grade heat recovery tank 4 absorbs the low-grade heat in the liquid flow channel. The third is in the cooler II 8. The heat exchange medium in the liquid flow channel of the cooler II 8 exchanges heat with the carbon dioxide in the air flow channel of the cooler II 8. The heat exchange medium absorbs the low-grade heat carried by the carbon dioxide and recovers it to the low-grade heat recovery tank 4 through the liquid flow channel.

[0066] The above system enables the recovery and utilization of low-grade energy during the cycle, thereby improving the cycle efficiency of the compressed carbon dioxide energy storage system.

[0067] In this invention, the air inlet and outlet are for carbon dioxide flow, and the airflow channel is for carbon dioxide flow. Even after gaseous carbon dioxide is converted to liquid, it continues to flow within the airflow channel. The liquid inlet and outlet are for the heat exchange medium flow, and the liquid flow channel is for the heat exchange medium flow. Both the airflow channel and the liquid flow channel are made of materials with good thermal conductivity. The heat exchange medium used in this invention is water or oil. The low-pressure gas storage tank, high-pressure gas storage tank, cooler, reheater, cold storage tank, heat storage tank, compressor, and expander used in this invention are all existing devices and will not be described in detail here.

[0068] In this embodiment, the liquid outlet of the high-pressure gas storage tank 5 is located on the side of the air inlet of the high-pressure gas storage tank 5; the liquid inlet of the high-pressure gas storage tank 5 is located on the side of the air outlet of the high-pressure gas storage tank 5; as Figure 2 As shown, Figure 2 The support structure is used to support the tank body 11 of the high-pressure gas storage tank;

[0069] The inlet and outlet of the high-pressure gas storage tank 5 are connected by a spiral liquid flow channel 18; the upper and lower sides of the spiral liquid flow channel 18 are in contact with the inner wall of the high-pressure gas storage tank 5, such as... Figure 2 As shown, the spiral liquid flow channel 18 is used to achieve counter-current heat exchange between the heat exchange medium in the spiral liquid flow channel and the carbon dioxide in the high-pressure gas storage tank. Counter-current heat exchange refers to the high-temperature fluid and the low-temperature fluid flowing in opposite directions in the heat exchanger, allowing the high-temperature fluid to heat the low-temperature fluid, thereby achieving heat transfer from the high-temperature fluid to the low-temperature fluid. In other words, in this invention, the heat exchange medium in the spiral liquid flow channel flows in the opposite direction to the carbon dioxide in the high-pressure gas storage tank. Using a spiral liquid flow channel can improve heat exchange efficiency and save space; furthermore, counter-current heat exchange can enhance heat transfer and make the temperature difference distribution more uniform.

[0070] In this embodiment, valves are provided at the air inlet, air outlet, liquid inlet, and liquid outlet of the high-pressure gas storage tank 5; valves may also be provided at the remaining air outlet, air inlet, liquid outlet, and liquid inlet, depending on the requirements. In this invention, except for the valves at the liquid inlet and liquid outlet of the high-pressure gas storage tank which are controlled by the control box 21, the other valves can be controlled manually or automatically. Automatic control uses existing automatic control valves.

[0071] In this embodiment, a temperature sensor 19 and a pressure sensor 20 are also included;

[0072] The temperature sensor 19 is installed inside the high-pressure gas storage tank 5 and is used to measure the temperature inside the high-pressure gas storage tank 5 and the temperature of the heat exchange medium inside the spiral liquid flow channel 18.

[0073] The pressure sensor 20 is installed inside the high-pressure gas storage tank 5 and is used to measure the pressure inside the high-pressure gas storage tank 5.

[0074] In this embodiment, a pump body (not shown in the figure), a control box 21, and a display screen 22 are also included;

[0075] The pump body's output port is connected to the liquid inlet of the high-pressure gas storage tank 5 and the liquid inlet of the cooler II 8. The pump body is used to draw in the heat exchange medium from the low-grade heat recovery tank 4 and input the heat exchange medium into the spiral liquid flow channel 18 or the liquid flow channel of the cooler II 8. The pump body is configured according to the heat exchange medium. When the heat exchange medium is water, an existing water pump is used; when the heat exchange medium is oil, an existing oil pump is used.

[0076] The input terminal of the control box 21 is connected to the output terminal of the temperature sensor 19 and the output terminal of the pressure sensor 20. The output terminal of the control box 21 is connected to the valve at the inlet of the high-pressure gas storage tank 5, the valve at the outlet of the high-pressure gas storage tank 5, and the output terminal of the pump body. The control box 21 is used to control the pump body to extract the heat exchange medium from the low-grade heat recovery tank 4 according to the temperature and pressure inside the high-pressure gas storage tank 5 and the temperature of the heat exchange medium, and to control the flow rate of the heat exchange medium by controlling the opening of the valve at the inlet of the high-pressure gas storage tank 5.

[0077] The input terminal of the display screen 22 is connected to the output terminal of the temperature sensor 19 and the output terminal of the pressure sensor 20, and is used to display the temperature in the high-pressure gas storage tank 5, the temperature of the heat exchange medium in the spiral liquid flow channel 18, and the pressure in the high-pressure gas storage tank 5.

[0078] In this invention, the control box calculates the required flow rate of the heat exchange medium based on the pressure in the high-pressure gas storage tank, the critical pressure to be reached, the temperature inside the tank, and the temperature in the heat exchange medium, thereby enabling the pressure in the high-pressure gas storage tank to reach the critical value. The calculation of the required flow rate of the heat exchange medium based on the existing pressure, the critical pressure to be reached, the temperature inside the tank, and the temperature in the heat exchange medium is existing technology and will not be elaborated upon here.

[0079] In this embodiment, both the high-pressure gas storage tank 5 and the low-pressure gas storage tank 1 are provided with drain ports at their bottoms; the bottoms with drain ports in this invention are in relative positions, and the position of the drain ports is related to the placement position of the gas storage tanks, such as... Figure 2 As shown, when the high-pressure gas tank is placed upside down, the drain outlet is located in the position shown in the figure. When the low-pressure gas tank is placed vertically, the drain outlet is located next to the gas outlet I of the low-pressure gas tank.

[0080] Valves are installed at the drain port 14 of the high-pressure gas storage tank 5 and the drain port (not shown in the figure) of the low-pressure gas storage tank 1. These drain ports are used to discharge impurities from the tanks, including impurities carried by carbon dioxide or oil stains. When carbon dioxide gas flows into the high-pressure gas storage tank 5, both the inlet and outlet valves are closed. At this time, there is no carbon dioxide gas in the low-pressure gas storage tank 1, and the drain valve can be opened to discharge the impurities. The same applies to the high-pressure gas storage tank 5. The drainage cycle is determined according to actual usage requirements. Discharging impurities from the gas storage tanks keeps them clean, extends equipment lifespan, and improves gas quality.

[0081] The carbon dioxide energy storage system provided by this invention comprises three processes:

[0082] Energy storage process: The low-pressure gas storage tank inputs carbon dioxide into the compressor, and the compressor converts electrical energy into pressure potential energy and heat energy, which are stored in the high-pressure gas storage tank and the heat storage tank respectively.

[0083] Energy release process: The high-pressure gas storage tank inputs the stored carbon dioxide into the reheater, and the reheater inputs the carbon dioxide into the expander to do work;

[0084] Recovery process: The expander inputs the carbon dioxide that has been released into cooler II, and cooler II inputs the cooled carbon dioxide into a low-pressure storage tank for storage.

[0085] Accordingly, the present invention also provides a constant-pressure energy release method based on the above-mentioned energy recovery type supercritical compressed carbon dioxide energy storage system, comprising the following steps:

[0086] S1. The low-pressure gas storage tank inputs low-pressure carbon dioxide into the compressor and compresses the low-pressure carbon dioxide to a high-temperature and high-pressure state;

[0087] S2. The compressor inputs high-temperature and high-pressure carbon dioxide into cooler I, and then from cooler I into the high-pressure storage tank; a low-grade heat recovery tank is used to heat the carbon dioxide in the high-pressure storage tank, so that the temperature of the carbon dioxide in the high-pressure storage tank is maintained within [AB, AC].

[0088] Where A represents the pseudo-critical point temperature of carbon dioxide in the high-pressure gas storage tank, [AB,AC] represents the temperature near the pseudo-critical point of carbon dioxide, AC represents the upper limit of the temperature near the pseudo-critical point of carbon dioxide, and AB represents the lower limit of the temperature near the pseudo-critical point of carbon dioxide.

[0089] S3. Open the valve at the outlet of the high-pressure gas storage tank to input the carbon dioxide in the high-pressure gas storage tank into the reheater. At the same time, the control box controls the flow rate Q of the heat exchange medium input spiral liquid flow channel of the low-grade heat recovery tank so that the real-time pressure of carbon dioxide in the high-pressure gas storage tank is equal to the preset pressure.

[0090] S4. The reheater receives carbon dioxide at a constant pressure and heats it, then inputs the heated carbon dioxide into the expander for constant-pressure energy release;

[0091] The constant-pressure energy release in this invention refers to the constant-pressure work done by carbon dioxide in the expander. Constant-pressure work means doing work on the external environment under constant system pressure. In this invention, the high-pressure gas storage tank receives carbon dioxide at a constant pressure, and the expander receives the carbon dioxide at a constant pressure and performs work on the external environment. Through the above steps, the temperature-sensitive characteristics of carbon dioxide near its quasi-critical point can be used to heat the carbon dioxide in the high-pressure gas storage tank, ensuring constant-pressure gas release, thereby achieving constant-pressure energy release.

[0092] In this embodiment, in step S1, the low-pressure gas storage tank inputs low-pressure carbon dioxide into the compressor and compresses the low-pressure carbon dioxide to a high temperature and high pressure state; the compressor uses surplus power from the power grid or electricity generated by the discharge of renewable energy to compress the carbon dioxide.

[0093] Among them, the high temperature and high pressure state refers to the temperature and pressure of carbon dioxide exceeding the critical temperature and critical pressure of carbon dioxide in the supercritical state. Supercritical is an existing concept and will not be elaborated here.

[0094] Low pressure refers to pressure much lower than the critical pressure of carbon dioxide (7.38 MPa); for example, 0.1 MPa. The specific low pressure standard is determined according to the requirements, but it must be below the critical pressure.

[0095] High pressure refers to pressure exceeding the critical pressure of carbon dioxide; high temperature refers to temperature exceeding 200 degrees Celsius.

[0096] In this embodiment, in step S2, the compressor inputs high-temperature and high-pressure carbon dioxide into cooler I, and then cooler I inputs it into high-pressure storage tank; a low-grade heat recovery tank is used to heat the carbon dioxide in the high-pressure storage tank, so that the temperature of the carbon dioxide in the high-pressure storage tank is maintained within [AB, AC].

[0097] Where A represents the pseudo-critical point temperature of carbon dioxide in the high-pressure gas storage tank, [AB, AC] represents the temperature near the pseudo-critical point of carbon dioxide, AC represents the upper limit of the temperature near the pseudo-critical point of carbon dioxide, and AB represents the lower limit of the temperature near the pseudo-critical point of carbon dioxide; C is 4, B is 8, and the unit is K (Kelvin). Taking 8MPa as an example, the pseudo-critical point temperature of carbon dioxide at 8MPa is approximately 308K, so the temperature near the pseudo-critical point of carbon dioxide is [300K, 304K]. The pseudo-critical state region refers to the region near the pseudo-critical point where the physical properties change drastically with temperature. The pseudo-critical point refers to the point where the specific heat capacity of a supercritical fluid reaches a peak during isobaric heating, and the point where the peak value appears is the pseudo-critical point.

[0098] Because carbon dioxide undergoes drastic changes in its physical properties when it is in the quasi-critical state region, its physical parameters are particularly sensitive to temperature changes. For example... Figure 3 As shown, taking a pressure of 8 MPa as an example, the pseudocritical temperature of carbon dioxide is 308 K. Its density decreases sharply with a slight increase in temperature around 308 K, and it has a large expansion coefficient around 308 K. This means that only a slight increase in temperature is needed to obtain a significant increase in pressure. Based on this characteristic, this invention uses the recovered low-grade heat to heat the high-pressure gas storage tank, thereby controlling the temperature inside the tank near the pseudocritical temperature. When the pressure inside the tank decreases, only a slight increase in heating temperature is needed to quickly compensate for the decrease in pressure inside the gas storage tank, thereby realizing the constant pressure discharge process of the energy storage system.

[0099] In this embodiment, in step S3, the valve of the outlet of the high-pressure gas storage tank is opened to input the carbon dioxide in the high-pressure gas storage tank into the reheater. At the same time, the control box controls the flow rate Q of the heat exchange medium input spiral liquid flow channel of the low-grade heat recovery tank so that the real-time pressure of carbon dioxide in the high-pressure gas storage tank is equal to the preset pressure.

[0100] The flow rate Q is calculated using the following formula:

[0101]

[0102] Where M represents the mass of carbon dioxide in the high-pressure gas storage tank, h d h represents the specific enthalpy of carbon dioxide in a high-pressure gas storage tank at a set pressure. r c represents the specific enthalpy of carbon dioxide in a high-pressure gas storage tank under real-time pressure. l t1 and t2 represent the specific heat capacity of the heat exchange medium, respectively, the start time and the time to heat carbon dioxide in the temperature range [AB, AC] of the low-grade heat recovery tank to the specified pressure, and dT represents the temperature change of the heat exchange medium in the spiral liquid flow channel in the high-pressure gas storage tank.

[0103] In this embodiment, hd and h r Calculated using the following formula:

[0104] hr = refpropm('h', 'T', T) g，r , 'P', P r (CO2)

[0105] h d =refpropm('h', 'P', P) d ,'D', ρ,'CO2')

[0106] Where refpropm represents a function, which is existing technology and will not be elaborated upon here; P d P represents the preset pressure of carbon dioxide in the high-pressure gas storage tank. r T represents the actual pressure of carbon dioxide in the high-pressure gas storage tank. g，r ρ represents the real-time temperature of carbon dioxide in the high-pressure storage tank, ρ represents the density of carbon dioxide in the high-pressure storage tank, 'h', 'T', 'P' and 'D' represent enthalpy, temperature, pressure and density respectively, and 'CO2' represents the working medium of carbon dioxide.

[0107] In this embodiment, in step S4, the reheater receives carbon dioxide at a constant pressure and heats it, and then inputs the heated carbon dioxide into the expander for constant-pressure energy release. Although the heat storage tank reheats the carbon dioxide at a constant pressure in the reheater, which changes the pressure of the output carbon dioxide to some extent, and there is pressure loss along the way during the output process, the change in pressure value is small and can be ignored.

[0108] Through the above steps, it is possible to ensure that carbon dioxide performs stable work on the expander, thereby achieving constant pressure energy release.

[0109] The invention also includes: connecting a generator to the output end of the expander, wherein when carbon dioxide does work at constant pressure in the expander, the expander drives the generator to work and generate stable electrical energy.

[0110] The invention also includes: inputting the carbon dioxide produced after the expander has completed its work into cooler II, cooling the carbon dioxide using the heat exchange medium in a low-grade heat recovery tank, and then inputting the cooled carbon dioxide into a low-pressure storage tank to complete one cycle. This method can save resources and protect the environment.

[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An energy recovery type supercritical compressed carbon dioxide energy storage system, characterized in that: It includes a low-pressure gas storage tank (1), a high-pressure gas storage tank (5), a compressor (2), a cooler I (3), a cooler II (8), a low-grade heat recovery tank (4), a heat storage tank (9), a cold storage tank (10), a reheater (6), and an expander (7). The outlet of the low-pressure gas storage tank (1) is connected to the inlet of the compressor (2), and the low-pressure gas storage tank (1) is used to store low-pressure carbon dioxide. The outlet of the compressor (2) is connected to the inlet of the cooler I (3), and the compressor (2) is used to compress low-pressure carbon dioxide into high-pressure carbon dioxide. The outlet of the cooler I (3) is connected to the inlet of the high-pressure gas storage tank (5) through an airflow channel, and the airflow channel between the outlet of the cooler I (3) and the inlet of the high-pressure gas storage tank (5) passes through the low-grade heat recovery tank (4). The cooler I (3) is used to cool down the compressed carbon dioxide and absorb the compression heat generated by the compressor (2). The outlet I of the low-grade heat recovery tank (4) is connected to the inlet of the high-pressure gas storage tank (5) through a liquid flow channel; the inlet I of the low-grade heat recovery tank (4) is connected to the outlet of the high-pressure gas storage tank (5) through a liquid flow channel; the low-grade heat recovery tank (4) is used to absorb the low-grade heat carried by the carbon dioxide output by the cooler I (3), and to provide low-grade heat to the high-pressure gas storage tank (5) through a heat exchange medium, so as to heat the carbon dioxide in the high-pressure gas storage tank (5) to a supercritical state, and keep the pressure of the carbon dioxide in the high-pressure gas storage tank (5) constant during the gas release process; The outlet of the high-pressure gas storage tank (5) is connected to the inlet of the reheater (6), and the high-pressure gas storage tank (5) is used to store high-pressure carbon dioxide. The outlet of the reheater (6) is connected to the inlet of the expander (7). The reheater (6) is used to heat supercritical carbon dioxide, so that the carbon dioxide in the reheater (6) becomes a high temperature and high pressure state. The outlet of the expander (7) is connected to the inlet of the cooler II (8), and the expander (7) is used to expand carbon dioxide at constant pressure to do work. The outlet of the cooler II (8) is connected to the inlet of the low-pressure gas storage tank (1), and the cooler II (8) is used to cool and reduce the temperature of the expanded carbon dioxide. The inlet of the cooler II (8) is connected to the outlet II of the low-grade heat recovery tank (4) through a liquid flow channel. The outlet of the cooler II (8) is connected to the inlet II of the low-grade heat recovery tank (4) through a liquid flow channel. The inlet of the cooler II (8) and the outlet of the cooler II (8) are connected through a liquid flow channel. The low-grade heat recovery tank (4) is also used to absorb the low-grade heat carried by carbon dioxide in the cooler II (8). The inlet of the heat storage tank (9) is connected to the outlet of the cooler I (3) through a liquid flow channel, and the outlet of the heat storage tank (9) is connected to the inlet of the reheater (6) through a liquid flow channel; the heat storage tank (9) stores the high-grade heat generated by the compressor (2) through a heat exchange medium, and provides high-grade heat to the reheater (6) through a heat exchange medium; The inlet of the cold storage tank (10) is connected to the outlet of the reheater (6) through a liquid flow channel, and the connected liquid flow channel passes through the low-grade heat recovery tank (4). The outlet of the cold storage tank (10) is connected to the inlet of the cooler I (3) through a liquid flow channel. The cold storage tank (10) is used to store the heat exchange medium cooled in the reheater (6) and to provide the cooled heat exchange medium to the cooler I (3). The low-grade heat recovery tank (4) is also used to absorb the low-grade heat in the heat exchange medium cooled in the reheater (6).

2. The energy recovery type supercritical compressed carbon dioxide energy storage system according to claim 1, characterized in that: The liquid outlet of the high-pressure gas storage tank (5) is located on the side of the air inlet of the high-pressure gas storage tank (5); the liquid inlet of the high-pressure gas storage tank (5) is located on the side of the air outlet of the high-pressure gas storage tank (5).

3. The energy recovery type supercritical compressed carbon dioxide energy storage system according to claim 2, characterized in that: The inlet of the high-pressure gas storage tank (5) and the outlet of the high-pressure gas storage tank (5) are connected by a spiral liquid flow channel; the spiral liquid flow channel is used to enable the heat exchange medium in the spiral liquid flow channel to achieve countercurrent heat exchange with the carbon dioxide in the high-pressure gas storage tank (5).

4. The energy recovery type supercritical compressed carbon dioxide energy storage system according to claim 3, characterized in that: The high-pressure gas storage tank (5) is equipped with valves at its air inlet, air outlet, liquid inlet, and liquid outlet.

5. The energy recovery type supercritical compressed carbon dioxide energy storage system according to claim 4, characterized in that: It also includes temperature sensors and pressure sensors; The temperature sensor is installed inside the high-pressure gas storage tank (5) and is used to measure the temperature inside the high-pressure gas storage tank (5) and the temperature of the heat exchange medium in the spiral liquid flow channel. The pressure sensor is installed inside the high-pressure gas storage tank (5) and is used to measure the pressure inside the high-pressure gas storage tank (5).

6. The energy recovery type supercritical compressed carbon dioxide energy storage system according to claim 5, characterized in that: It also includes the pump body, control box, and display screen; The pump body's output port is connected to the liquid inlet of the high-pressure gas storage tank (5) and the liquid inlet of the cooler II (8). The pump body is used to draw in the heat exchange medium in the low-grade heat recovery tank (4) and input the heat exchange medium into the spiral liquid flow channel (18) or the liquid flow channel of the cooler II (8). The input end of the control box is connected to the output end of the temperature sensor and the output end of the pressure sensor. The output end of the control box is connected to the valve at the inlet of the high-pressure gas storage tank (5), the valve at the outlet of the high-pressure gas storage tank (5), and the output end of the pump body. The control box is used to control the pump body to extract the heat exchange medium in the low-grade heat recovery tank (4) according to the temperature and pressure inside the high-pressure gas storage tank (5) and the temperature of the heat exchange medium. The control box also controls the flow rate of the heat exchange medium by controlling the opening degree of the valve at the inlet of the high-pressure gas storage tank (5). The input terminal of the display screen is connected to the output terminal of the temperature sensor and the output terminal of the pressure sensor, and is used to display the temperature in the high-pressure gas storage tank (5), the temperature of the heat exchange medium in the spiral liquid flow channel, and the pressure in the high-pressure gas storage tank (5).

7. The energy recovery type supercritical compressed carbon dioxide energy storage system according to claim 1, characterized in that: Both the high-pressure gas storage tank (5) and the low-pressure gas storage tank (1) are provided with drain ports at their bottoms; valves are provided at the drain ports of both the high-pressure gas storage tank (5) and the low-pressure gas storage tank (1), and the drain ports of both the high-pressure gas storage tank (5) and the low-pressure gas storage tank (1) are used to discharge the impurities inside the tanks.

8. A constant-pressure energy release method based on the energy recovery type supercritical compressed carbon dioxide energy storage system according to any one of claims 1-7, characterized in that: Includes the following steps: S1. The low-pressure gas storage tank inputs low-pressure carbon dioxide into the compressor and compresses the low-pressure carbon dioxide to a high-temperature and high-pressure state; S2. The compressor inputs high-temperature and high-pressure carbon dioxide into cooler I, and then from cooler I into the high-pressure storage tank; a low-grade heat recovery tank is used to heat the carbon dioxide in the high-pressure storage tank, so that the temperature of the carbon dioxide in the high-pressure storage tank is maintained within [AB, AC]. Where A represents the pseudo-critical point temperature of carbon dioxide in the high-pressure gas storage tank, [AB,AC] represents the temperature near the pseudo-critical point of carbon dioxide, AC represents the upper limit of the temperature near the pseudo-critical point of carbon dioxide, and AB represents the lower limit of the temperature near the pseudo-critical point of carbon dioxide. S3. Open the valve at the outlet of the high-pressure gas storage tank to input the carbon dioxide in the high-pressure gas storage tank into the reheater. At the same time, the control box controls the flow rate Q of the heat exchange medium input spiral liquid channel of the low-grade heat recovery tank so that the real-time pressure of carbon dioxide in the high-pressure gas storage tank is equal to the preset pressure. S4. The reheater receives carbon dioxide at a constant pressure and heats it, then inputs the heated carbon dioxide into the expander for constant-pressure energy release.

9. The constant-pressure energy release method according to claim 8, characterized in that: In step S3, the flow rate Q is calculated using the following formula: Where M represents the mass of carbon dioxide in the high-pressure gas storage tank. This indicates the specific enthalpy of carbon dioxide in a high-pressure gas storage tank at a set pressure. This represents the specific enthalpy of carbon dioxide in a high-pressure gas storage tank under real-time pressure. This indicates the specific heat capacity of the heat exchange medium. and dT represents the start time and time to reach a specified pressure for heating carbon dioxide within the temperature range [AB, AC] in the low-grade heat recovery tank, respectively, and dT represents the temperature change of the heat exchange medium in the spiral liquid flow channel within the high-pressure gas storage tank.

10. The constant-pressure energy release method according to claim 9, characterized in that: and Calculated using the following formula: in, Represents a function, This indicates the preset pressure of carbon dioxide in the high-pressure gas storage tank. This indicates the actual pressure of carbon dioxide in the high-pressure gas storage tank. This indicates the real-time temperature of carbon dioxide in the high-pressure gas storage tank. This indicates the density of carbon dioxide in the high-pressure gas storage tank. , , and These represent enthalpy, temperature, pressure, and density, respectively. The working medium representing carbon dioxide.

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