Compressed carbon dioxide energy storage system for double-liquid storage

Abstract

The invention relates to the technical field of compressed carbon dioxide energy storage, and provides a double-liquid-state storage compressed carbon dioxide energy storage system, which comprises a heat pump loop, a first multi-stream heat regenerator, a compressor, a cooler and a first turbine, a second multi-stream heat regenerator, a second multi-stream heat regenerator, a second multi-stream heat regenerator, a second multi-stream heat regenerator, a second multi-stream heat regenerator, a second multi-stream heat regenerator and a second turbine, and the power generation loop comprises a high-pressure CO2 liquid storage tank, a high-pressure working medium pump, a second multi-stream heat regenerator, a heater, a second turbine, a precooler and a condenser. CO2 flows in the heat pump loop and the power generation loop to serve as a working medium, and low-pressure CO2 liquid and high-pressure CO2 liquid are stored in the low-pressure CO2 liquid storage tank and the high-pressure CO2 liquid storage tank and used for the heat pump loop and the power generation loop respectively. By using the CO2 liquid, the pressure in the tank can be maintained during release, the output flow is ensured, and the output of the system is stable. And meanwhile, CO2 liquid can be output through the high-pressure working medium pump, pressure loss caused by throttling is avoided, and the energy storage efficiency is improved. And through liquid storage tank storage, the storage tank volume can be reduced, and the energy storage cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of compressed carbon dioxide energy storage, and in particular to a compressed carbon dioxide energy storage system with dual liquid storage. Background Art

[0002] Energy storage technology is an important means to achieve a high proportion of renewable energy access to the power grid. It can improve the grid's ability to accept renewable energy, reduce peak loads, participate in frequency and voltage regulation, and thus improve the overall efficiency and economy of the power system. This not only helps to improve power quality, but also reduces operating costs. In general, in order to achieve a stable power grid and a high penetration rate of renewable energy, low-cost, high-efficiency, large-capacity and environmentally friendly energy storage technology is needed.

[0003] Compressed Carbon Dioxide Energy Storage (CCES) technology is a new energy storage technology developed based on the traditional compressed air energy storage (CAES) and Brayton cycle principles. It uses carbon dioxide (CO2) as the working medium to store and release energy through the process of compression, storage and expansion. This technology has the advantages of high energy density, long life, compact system equipment, etc., and has good development prospects, especially suitable for dealing with the intermittent and instability of renewable energy.

[0004] The CO2 storage tank of the traditional compressed carbon dioxide energy storage system is a gas storage tank, and a throttle valve is installed at the outlet of the storage tank. When the CO2 working fluid is needed, the throttle valve is opened to output CO2. This design has the following disadvantages: First, the pressure of CO2 decreases after passing through the throttle valve, and a part of the pressure energy is lost, which reduces the efficiency of the system; second, when the quality of CO2 in the storage tank decreases, the pressure decreases, the pressure difference before and after the throttle valve decreases, and the flow rate decreases accordingly, making the output of the energy storage system unstable; finally, the density of CO2 gas is lower than that of liquid, and the volume of the storage tank is large, which increases the cost of system construction. Summary of the invention

[0005] In response to the above problems, the present invention provides a dual-liquid storage compressed carbon dioxide energy storage system, which stores the CO2 working fluid used in the heat pump circuit and the power generation circuit in the form of low-pressure CO2 liquid and high-pressure CO2 liquid respectively. When the CO2 liquid is released, the pressure in the liquid storage tank can be maintained to ensure the stability of the output flow, so that the energy storage system can output stably. In addition, the high-pressure CO2 liquid in the high-pressure CO2 liquid storage tank can be output through a high-pressure working fluid pump to avoid the pressure loss caused by throttling, effectively improving the energy storage efficiency of the system. In addition, storage in liquid form can reduce the volume of the storage tank and reduce the energy storage cost.

[0006] The present invention provides a dual-liquid storage compressed carbon dioxide energy storage system, comprising:

[0007] The heat pump circuit includes a low-pressure CO2 liquid storage tank, a throttle valve, an evaporator, a first multi-stream heat regenerator, a compressor and a cooler which are connected in sequence, and the cooler is further connected to the first turbine through the first multi-stream heat regenerator;

[0008] The power generation circuit includes a high-pressure CO2 liquid storage tank connected to the first turbine, a high-pressure working fluid pump connected to the high-pressure CO2 liquid storage tank in sequence, a second multi-stream heat exchanger, a heater, and a second turbine, and the second turbine is connected to a precooler and a condenser in sequence through the second multi-stream heat exchanger, and the condenser is connected to the low-pressure CO2 liquid storage tank.

[0009] Among them, CO2 is circulated as a working fluid in the heat pump circuit and the power generation circuit, low-pressure CO2 liquid is stored in the low-pressure CO2 liquid storage tank, the low-pressure CO2 liquid forms high-pressure CO2 liquid after passing through the heat pump circuit and is stored in the high-pressure CO2 liquid storage tank, and the high-pressure CO2 liquid is restored to low-pressure CO2 liquid after passing through the power generation circuit and is stored in the low-pressure CO2 liquid storage tank.

[0010] According to the above technical solution, high-pressure CO2 liquid and low-pressure CO2 liquid are stored in high-pressure CO2 liquid storage tanks and low-pressure CO2 liquid storage tanks respectively. When releasing CO2 liquid, part of the liquid CO2 in the corresponding liquid storage tank will evaporate into gas to maintain the pressure in the tank, thereby ensuring the stability of the CO2 working fluid output flow rate and further ensuring the stable output of the system. In addition, storing the working fluid in liquid form can effectively reduce the volume of the storage tank and reduce the energy storage cost. In addition, the high-pressure CO2 liquid in the high-pressure CO2 liquid storage tank can be output through a high-pressure working fluid pump to avoid pressure loss caused by throttling and improve the energy storage efficiency of the system.

[0011] In an optional technical solution of the present invention, a heat storage circuit is further provided between the cooler, the first multi-stream heat regenerator, the second multi-stream heat regenerator and the heater. The cooler and the first multi-stream heat regenerator absorb the thermal energy of the working fluid in the heat pump circuit and store it in the heat storage circuit, and release the thermal energy to the second multi-stream heat regenerator and the heater through the heat storage circuit to heat the working fluid in the power generation circuit. A heat storage medium hot tank and a heat storage medium cold tank are provided in the energy storage circuit. The inlet of the heat storage medium hot tank is connected to the medium outlet of the cooler and the first multi-stream heat regenerator, the outlet of the heat storage medium hot tank is connected to the medium inlet of the second multi-stream heat regenerator and the heater, the inlet of the heat storage medium cold tank is connected to the medium outlet of the second multi-stream heat regenerator and the heater, and the outlet of the heat storage medium cold tank is connected to the medium inlet of the cooler and the first multi-stream heat regenerator.

[0012] According to this technical solution, the heat energy generated by compression in the heat pump circuit is stored in the heat storage circuit, and is used to heat the working fluid in the power generation circuit, thereby making full use of the heat energy, reducing energy waste, improving the energy storage efficiency of the system, and providing a stable heat source, which can enable the system to operate stably.

[0013] In an optional technical solution of the present invention, a heat storage medium hot tank is provided with a first high-grade chamber and a first low-grade chamber which are separated from each other, a heat storage medium cold tank is provided with a second high-grade chamber and a second low-grade chamber which are separated from each other, high-grade heat storage medium flows through both the cooler and the heater, the high-grade heat storage medium absorbs high-grade thermal energy of the working fluid in the cooler, and releases high-grade thermal energy in the heater, and the cooler, the first high-grade chamber, the heater, and the second high-grade chamber are sequentially connected to circulate the high-grade heat storage medium.

[0014] According to the technical solution, the high-grade thermal energy can be collected, stored and used separately by the first high-grade chamber and the second high-grade chamber, which is convenient for independent use of the high-grade thermal energy absorbed in the heat pump circuit to heat the working fluid in the power generation circuit to a high-temperature state that can expand and do work, so that the stored and released thermal energy are matched, thereby reducing the heat exchange end difference and reducing damage.

[0015] In an optional technical solution of the present invention, a low-grade heat storage medium flows through both the first multi-stream heat regenerator and the second multi-stream heat regenerator, and the low-grade heat storage medium absorbs the low-grade thermal energy of the working fluid in the first multi-stream heat regenerator, and releases the low-grade thermal energy in the second multi-stream heat regenerator, and the first multi-stream heat regenerator, the first low-grade chamber, the second multi-stream heat regenerator, and the second low-grade chamber are sequentially connected to circulate the low-grade heat storage medium.

[0016] According to the technical solution, the low-grade thermal energy can be separately collected, stored and used by the separated first low-grade chamber and the second low-grade chamber, which is convenient for independently using the low-grade thermal energy to preheat the working fluid and fully utilize the thermal energy.

[0017] In an optional technical solution of the present invention, the first multi-stream heat regenerator comprises a first low-temperature working fluid flow channel, a first high-temperature working fluid flow channel and a second high-temperature working fluid flow channel, the inlet of the first low-temperature working fluid flow channel is connected to the working fluid outlet of the evaporator, the outlet of the first low-temperature working fluid flow channel is connected to the working fluid inlet of the compressor, the first low-temperature working fluid flow channel carries working fluid evaporated by the evaporator, the inlets of the first high-temperature working fluid flow channel and the second high-temperature working fluid flow channel are both connected to the working fluid outlet of the cooler, the outlets of the first high-temperature working fluid flow channel and the second high-temperature working fluid flow channel are both connected to the working fluid inlet of the first turbine, the first high-temperature working fluid flow channel and the second high-temperature working fluid flow channel carry working fluid after high-grade thermal energy is absorbed, the low-grade heat storage medium absorbs low-grade thermal energy by heat exchange with the first high-temperature working fluid flow channel, and the working fluid in the first low-temperature working fluid flow channel is reheated by heat exchange with the second high-temperature working fluid flow channel.

[0018] According to the technical solution, the working fluid after high-grade thermal energy is absorbed is divided into two parts through the first high-temperature working fluid flow channel and the second high-temperature working fluid flow channel. The first high-temperature working fluid flow channel exchanges heat with the low-grade heat storage medium to enable the medium to store low-grade thermal energy. At the same time, the second high-temperature working fluid flow channel directly utilizes the low-grade thermal energy to recover the working fluid in the first low-temperature working fluid flow channel, which can make full use of the low-grade thermal energy and effectively reduce the heat in the heat pump circuit. damage.

[0019] In an optional technical solution of the present invention, a second multi-stream heat exchanger is provided with a second low-temperature working fluid flow channel and a third high-temperature working fluid flow channel, the inlet of the second low-temperature working fluid flow channel is connected to the working fluid outlet of the high-pressure working fluid pump, the outlet of the second low-temperature working fluid flow channel is connected to the working fluid inlet of the heater, the second low-temperature working fluid flow channel has working fluid pressurized by the high-pressure working fluid pump flowing through it, the inlet of the third high-temperature working fluid flow channel is connected to the working fluid outlet of the second turbine, the outlet of the third high-temperature working fluid flow channel is connected to the working fluid inlet of the precooler, the third high-temperature working fluid flow channel has working fluid with residual heat after expansion and work done by the second turbine, and the working fluid in the second low-temperature working fluid flow channel is preheated by the low-grade thermal energy of the low-grade energy storage medium and the residual heat of the working fluid in the third high-temperature working fluid flow channel.

[0020] According to this technical solution, while using low-grade thermal energy to preheat the working fluid in the power generation circuit, the third high-temperature working fluid flow channel also uses the waste heat of the working fluid after expansion to preheat the working fluid, thereby achieving full utilization of thermal energy.

[0021] In an optional technical solution of the present invention, a cold storage circuit is further provided between the evaporator and the condenser, through which the cold storage circuit stores the cold energy released by the working fluid in the heat pump circuit, and the working fluid in the power generation circuit is cooled by the stored cold energy, a cold storage medium cold tank and a cold storage medium hot tank are provided in the cold storage circuit, and cold storage medium flows through both the evaporator and the condenser, the cold storage medium absorbs cold energy in the evaporator, and releases cold energy in the condenser, and the evaporator, the cold storage medium cold tank, the condenser, and the cold storage medium hot tank are connected in sequence to circulate the cold storage medium.

[0022] According to this technical solution, the cold energy generated by the evaporation of low-pressure CO2 liquid can be stored through a cold storage circuit, and the condenser released into the power generation circuit can further cool the CO2 working fluid into low-pressure CO2 liquid for storage, thereby making full use of the cold energy.

[0023] In the optional technical solution of the present invention, the storage pressures of the low-pressure CO2 liquid storage tank and the high-pressure CO2 liquid storage tank are both 1MPa-7.38MPa, the storage temperature of the low-pressure CO2 liquid storage tank is -40℃-5℃, the storage temperature of the high-pressure CO2 liquid storage tank is 30℃, and the low-pressure CO2 liquid in the low-pressure CO2 liquid storage tank and the high-pressure CO2 liquid in the high-pressure CO2 liquid storage tank are both in a saturated liquid state.

[0024] According to this technical solution, low-pressure CO2 liquid and high-pressure CO2 liquid can be stably stored at corresponding storage pressure and temperature, and the liquid in the tank is in a saturated liquid state of gas-liquid equilibrium. When the liquid is released, part of the liquid in the tank will evaporate into gas to maintain the pressure in the tank, thereby ensuring the stability of the output flow and further ensuring the stability of the system output. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural diagram of a compressed carbon dioxide energy storage system with dual liquid storage in an embodiment of the present invention.

[0026] Figure numerals: low-pressure CO2 liquid storage tank 1, throttle valve 2, evaporator 3, first multi-stream heat regenerator 4, first low-temperature working fluid flow channel 41, compressor 5, cooler 6, first turbine 7, high-pressure CO2 liquid storage tank 8, high-pressure working fluid pump 9, second multi-stream heat regenerator 10, second low-temperature working fluid flow channel 101, third high-temperature working fluid flow channel 102, heater 11, second turbine 12, precooler 13, condenser 14, heat storage medium hot tank 15, heat storage medium cold tank 16, cold storage medium cold tank 17, cold storage medium hot tank 18. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] Figure 1 It is a structural diagram of a compressed carbon dioxide energy storage system with dual liquid storage in an embodiment of the present invention.

[0029] like Figure 1 As shown, the compressed carbon dioxide energy storage system with dual liquid storage in this embodiment includes a heat pump circuit, a power generation circuit, a heat storage circuit and a cold storage circuit.

[0030] The heat pump circuit includes a low-pressure CO2 liquid storage tank 1, a throttle valve 2, an evaporator 3, a first multi-stream heat regenerator 4, a compressor 5 and a cooler 6 which are connected in sequence, and the cooler 6 is further connected to the first turbine 7 through the first multi-stream heat regenerator 4.

[0031] The power generation circuit includes a high-pressure CO2 liquid storage tank 8 connected to the first turbine 7, a high-pressure working fluid pump 9 connected to the high-pressure CO2 liquid storage tank 8 in sequence, a second multi-stream heat regenerator 10, a heater 11 and a second turbine 12, and the second turbine 12 is connected to a precooler 13 and a condenser 14 in sequence through the second multi-stream heat regenerator 10, and the condenser 14 is connected to the low-pressure CO2 liquid storage tank 1.

[0032] CO2 is circulated as a working fluid in the heat pump circuit and the power generation circuit. Low-pressure liquid CO2 is stored in the low-pressure CO2 liquid storage tank 1. The low-pressure liquid CO2 forms high-pressure liquid CO2 after passing through the heat pump circuit and is stored in the high-pressure CO2 liquid storage tank 8. The high-pressure liquid CO2 is restored to low-pressure liquid CO2 after passing through the power generation circuit and is stored in the low-pressure CO2 liquid storage tank 1.

[0033] Specifically, the low-pressure CO2 liquid in the low-pressure CO2 liquid storage tank 1 is released and evaporated, and the CO2 working fluid is compressed into a high-pressure working fluid through a heat pump circuit. After heat exchange and expansion work, high-pressure CO2 liquid is formed and stored in the high-pressure CO2 liquid storage tank 8, and the compression heat of CO2 is transferred into the heat storage circuit.

[0034] The power generation circuit utilizes the high-pressure CO2 liquid in the high-pressure CO2 liquid storage tank 8 and the heat energy stored in the heat storage circuit to expand and generate electricity. After the expansion and work, the CO2 working fluid releases waste heat, is pre-cooled and further condensed to form low-pressure CO2 liquid that is stored in the low-pressure CO2 liquid storage tank 1.

[0035] At the same time, the heat storage circuit is used to store the heat energy released in the heat pump circuit and transfer the heat energy to the power generation circuit when generating electricity; the cold storage circuit is used to store the cold energy released by the low-temperature CO2 working fluid in the heat pump circuit, and use the stored cold energy to condense the CO2 working fluid after expansion and work in the power generation circuit.

[0036] In this embodiment, high-pressure CO2 liquid and low-pressure CO2 liquid are stored respectively by using a high-pressure CO2 liquid storage tank 8 and a low-pressure CO2 liquid storage tank 1. When the CO2 liquid is released, the pressure in the tank decreases, and part of the liquid CO2 in the corresponding liquid storage tank will evaporate into gas to maintain the pressure in the tank, thereby ensuring the stability of the CO2 working fluid output flow rate, and further ensuring the stable output of the system. In addition, storing the working fluid in liquid form can effectively reduce the volume of the storage tank and reduce the energy storage cost. In addition, the high-pressure CO2 liquid in the high-pressure CO2 liquid storage tank 8 can also be output through the high-pressure working fluid pump 9 to avoid the pressure loss caused by throttling and improve the energy storage efficiency of the system.

[0037] Furthermore, the storage pressures of the low-pressure CO2 liquid storage tank 1 and the high-pressure CO2 liquid storage tank 8 are both 1MPa-7.38MPa, the storage temperature of the low-pressure CO2 liquid storage tank 1 is -40℃-5℃, the storage temperature of the high-pressure CO2 liquid storage tank 8 is 30℃, and the low-pressure CO2 liquid in the low-pressure CO2 liquid storage tank 1 and the high-pressure CO2 liquid in the high-pressure CO2 liquid storage tank 8 are both in a saturated liquid state.

[0038] In this embodiment, the storage pressure and temperature of the low-pressure CO2 liquid storage tank 1 and the high-pressure CO2 liquid storage tank 8 are set accordingly, so that the low-pressure CO2 liquid and the high-pressure CO2 liquid are stably stored at the corresponding storage pressure and temperature. In addition, the liquid in the tank is in a saturated liquid state of gas-liquid equilibrium. When the liquid is released, part of the liquid in the tank will evaporate into gas to maintain the pressure in the tank, thereby ensuring the output flow stability to further ensure the stability of the system output.

[0039] In this embodiment, the maximum pressure in the heat pump circuit is higher than the critical pressure.

[0040] Furthermore, the heat pump circuit is not limited to a single-stage compression mode, but also includes a multi-stage compression mode; the power generation circuit is not limited to a single-stage expansion mode, but also includes a multi-stage expansion mode, and the cooling medium of the precooler 13 in the power generation circuit includes air, water, seawater, etc.

[0041] The heat storage circuit is arranged between the cooler 6, the first multi-stream heat regenerator 4, the second multi-stream heat regenerator 10, and the heater 11. The cooler 6 and the first multi-stream heat regenerator 4 absorb the thermal energy of the working fluid in the heat pump circuit and store it in the heat storage circuit, and release the thermal energy to the second multi-stream heat regenerator 10 and the heater 11 through the heat storage circuit to heat the working fluid in the power generation circuit.

[0042] A heat storage medium hot tank 15 and a heat storage medium cold tank 16 are provided in the heat storage circuit. The inlet of the heat storage medium hot tank 15 is connected to the medium outlet of the cooler 6 and the first multi-stream regenerator 4, and the outlet of the heat storage medium hot tank 15 is connected to the medium inlet of the second multi-stream regenerator 10 and the heater 11. The inlet of the heat storage medium cold tank 16 is connected to the medium outlet of the second multi-stream regenerator 10 and the heater 11, and the outlet of the heat storage medium cold tank 16 is connected to the medium inlet of the cooler 6 and the first multi-stream regenerator 4.

[0043] Furthermore, the heat storage medium hot tank 15 has a first high-grade chamber (not shown in the figure) and a first low-grade chamber (not shown in the figure) which are separated from each other, and the heat storage medium cold tank 16 has a second high-grade chamber (not shown in the figure) and a second low-grade chamber (not shown in the figure) which are separated from each other.

[0044] High-grade heat storage medium flows through both the cooler 6 and the heater 11. The high-grade heat storage medium absorbs the high-grade thermal energy of the working fluid in the cooler 6 and releases the high-grade thermal energy in the heater 11. The cooler 6, the first high-grade chamber, the heater 11, and the second high-grade chamber are connected in sequence to circulate the high-grade heat storage medium.

[0045] A low-grade heat storage medium flows through both the first multi-stream heat regenerator 4 and the second multi-stream heat regenerator 10. The low-grade heat storage medium absorbs the low-grade heat energy of the working medium in the first multi-stream heat regenerator 4 and releases the low-grade heat energy in the second multi-stream heat regenerator 10. The first multi-stream heat regenerator 4, the first low-grade chamber, the second multi-stream heat regenerator 10, and the second low-grade chamber are sequentially connected to circulate the low-grade heat storage medium.

[0046] In this embodiment, high-grade heat storage medium and low-grade heat storage medium are used to collect, store and circulate high-grade heat energy and low-grade heat energy respectively, so that the heat energy stored in the heat pump circuit and the heat energy released in the power generation circuit can be matched, effectively reducing the heat exchange end difference and reducing loss, further improving the working efficiency of the entire system.

[0047] Furthermore, the heat storage medium is not limited to common sensible heat storage fluids such as high-pressure water and molten salt, but also includes latent heat storage fluids such as paraffin, salts (such as sodium nitrate, sodium acetate), organic compounds, etc., as well as thermochemical heat storage fluids.

[0048] In this embodiment, the sealing performance must be ensured between the first high-grade chamber and the first low-grade chamber, and between the second high-grade chamber and the second low-grade chamber, so that high-grade thermal energy and low-grade thermal energy can be stored separately.

[0049] In some embodiments, high / low grade energy storage media can be stored separately by setting up multiple heat storage medium hot tanks 15 and heat storage medium cold tanks 16. Specifically, the multiple heat storage medium hot tanks 15 include high-grade hot tanks and low-grade hot tanks, and the multiple heat storage medium cold tanks 16 include high-grade cold tanks and low-grade cold tanks. The cooler 6, the high-grade hot tank, the heater 11, and the high-grade cold tank are connected in sequence to circulate the high-grade heat storage medium; the first multi-stream heat exchanger 4, the low-grade hot tank, the second multi-stream heat exchanger 10, and the low-grade cold tank are connected in sequence to circulate the low-grade heat storage medium. By setting up heat storage medium hot tanks 15 and heat storage medium cold tanks 16 for storing high / low grade energy storage media separately, it is also possible to achieve separate collection, storage, circulation and use of high-grade thermal energy and low-grade thermal energy.

[0050] Furthermore, the first multi-stream heat exchanger 4 has a first low-temperature working fluid flow channel 41, a first high-temperature working fluid flow channel (not shown in the figure), and a second high-temperature working fluid flow channel (not shown in the figure). The inlet of the first low-temperature working fluid flow channel 41 is connected to the working fluid outlet of the evaporator 3, and the outlet of the first low-temperature working fluid flow channel 41 is connected to the working fluid inlet of the compressor 5. The first low-temperature working fluid flow channel 41 is circulated with the working fluid evaporated by the evaporator 3. The inlets of the first high-temperature working fluid flow channel and the second high-temperature working fluid flow channel are both connected to the working fluid outlet of the cooler 6, and the outlets of the first high-temperature working fluid flow channel and the second high-temperature working fluid flow channel are both connected to the working fluid inlet of the first turbine, and the first high-temperature working fluid flow channel and the second high-temperature working fluid flow channel are circulated with the working fluid after high-grade thermal energy is absorbed. The low-grade heat storage medium absorbs low-grade thermal energy by heat exchange with the first high-temperature working fluid flow channel, and the working fluid in the first low-temperature working fluid flow channel 41 is reheated by heat exchange with the second high-temperature working fluid flow channel.

[0051] In this embodiment, the working fluid after high-grade thermal energy is absorbed is divided into two parts through the first high-temperature working fluid flow channel and the second high-temperature working fluid flow channel. The first high-temperature working fluid flow channel exchanges heat with the low-grade heat storage medium to enable the medium to store low-grade thermal energy. At the same time, the second high-temperature working fluid flow channel directly utilizes the low-grade thermal energy to recover the working fluid in the first low-temperature working fluid flow channel 41, which can make full use of the low-grade thermal energy and effectively reduce the heat in the heat pump circuit. damage.

[0052] Further, the second multi-stream regenerator 10 has a second low-temperature working fluid flow channel 101 and a third high-temperature working fluid flow channel 102. The inlet of the second low-temperature working fluid flow channel 101 is connected to the working fluid outlet of the high-pressure working fluid pump 9, and the outlet of the second low-temperature working fluid flow channel 101 is connected to the working fluid inlet of the heater 11. The second low-temperature working fluid flow channel 101 has working fluid pressurized by the high-pressure working fluid pump 9 flowing therein. The inlet of the third high-temperature working fluid flow channel 102 is connected to the working fluid outlet of the second turbine 12, and the outlet of the third high-temperature working fluid flow channel 102 is connected to the working fluid inlet of the precooler 13. The third high-temperature working fluid flow channel 102 has working fluid with residual heat after expansion and work by the second turbine 12. The working fluid in the second low-temperature working fluid flow channel 101 is preheated by the low-grade heat energy of the low-grade energy storage medium and the residual heat of the working fluid in the third high-temperature working fluid flow channel 102.

[0053] Through the second multi-stream heat regenerator 10, this embodiment uses low-grade thermal energy to preheat the working fluid in the power generation circuit, and also uses the waste heat of the working fluid after expansion and work to preheat through the third high-temperature working fluid flow channel 102, thereby achieving full utilization of thermal energy.

[0054] In addition, in this embodiment Figure 1 The shapes and positions of the various flow channels illustrated are for illustrative purposes only and should not constitute a limitation on the flow channel structure. Technicians can adjust the shapes and positions of the flow channels as needed to achieve sufficient heat exchange.

[0055] The cold storage circuit is arranged between the evaporator 3 and the condenser 14. The cold storage circuit stores the cold energy released by the working fluid in the heat pump circuit, and cools the working fluid in the power generation circuit by the stored cold energy. The cold storage circuit is provided with a cold storage medium cold tank 17 and a cold storage medium hot tank 18. The cold storage medium flows through both the evaporator 3 and the condenser 14. The cold storage medium absorbs cold energy in the evaporator 3 and releases cold energy in the condenser 14. The evaporator 3, the cold storage medium cold tank 17, the condenser 14, and the cold storage medium hot tank 18 are connected in sequence to circulate the cold storage medium.

[0056] In this embodiment, the cold energy generated by the evaporation of the low-pressure CO2 liquid can be stored through the cold storage circuit, and the condenser 14 released to the power generation circuit can further cool the pre-cooled CO2 working fluid into a low-pressure CO2 liquid for storage, thereby making full use of the cold energy and providing a stable cold source.

[0057] Furthermore, the cold storage process is not limited to the common water storage, but also includes ice storage, hydrate storage, eutectic salt storage and other cold storage methods.

[0058] The working process of the dual liquid storage compressed carbon dioxide energy storage system in this embodiment is as follows:

[0059] In the heat pump circuit, the low-pressure CO2 liquid in the low-pressure CO2 liquid storage tank 1 is released and passes through the throttle valve 2. At the outlet of the throttle valve 2, the low-pressure CO2 liquid expands into a two-phase flow fluid and enters the evaporator 3 to absorb heat and evaporate into CO2 gas. The cold storage medium in the evaporator 3 absorbs cold energy and enters the cold storage circuit. The CO2 gas at the outlet of the evaporator 3 enters the first low-temperature working fluid flow channel 41 of the first multi-stream regenerator 4 and absorbs the heat from the CO2 fluid in the second high-temperature working fluid flow channel to heat up, and then enters the compressor 5 to be compressed into a high-temperature supercritical fluid. The high-temperature fluid at the outlet of the compressor 5 first enters the cooler 6 to transfer the high-grade heat energy to the high-grade energy storage medium, and the high-grade energy storage medium enters the heat storage circuit. The CO2 fluid after high-grade heat energy is absorbed enters the first high-temperature working fluid flow channel and the second high-temperature working fluid flow channel of the first multi-stream heat regenerator 4 respectively, and the low-grade heat energy is transferred to the low-grade heat storage medium through the first high-temperature working fluid flow channel. The low-grade energy storage medium enters the heat storage loop, and at the same time, the CO2 fluid after high-grade heat energy is absorbed preheats the CO2 fluid in the first low-temperature working fluid flow channel 41 through the second high-temperature working fluid flow channel. The CO2 fluid after heat exchange cooling finally enters the first turbine 7 to recover part of the expansion work, and forms high-pressure CO2 liquid to be stored in the high-pressure CO2 liquid storage tank 8.

[0060] In the power generation circuit, after the high-pressure CO2 liquid in the high-pressure CO2 liquid storage tank 8 is released and compressed to a higher pressure by the high-pressure working fluid pump 9, it enters the second low-temperature working fluid flow channel 101 of the second multi-stream heat exchanger 10, and is preheated by absorbing the low-grade heat energy in the low-grade heat storage medium and the waste heat of the CO2 fluid after expansion and work in the third high-temperature working fluid flow channel 102. Then it enters the heater 11 to absorb the high-grade heat energy in the high-grade heat storage medium to reach the specified temperature to form a high-temperature and high-pressure CO2 fluid, and enters the second turbine 12 to expand and generate electricity. After the expansion and work, the CO2 fluid first enters the third high-temperature working fluid flow channel 102 to release part of the waste heat and then enters the precooler 13 for further cooling. Finally, the CO2 working fluid enters the condenser 14 to absorb the cold energy stored in the cold storage medium. After the CO2 working fluid is condensed to a liquid state, it forms a low-pressure CO2 liquid, which is transported to the low-pressure CO2 liquid storage tank 1 for storage, completing the cycle.

[0061] The high-grade heat storage medium is stored in the first high-grade chamber of the heat storage medium hot tank 15 and the second high-grade chamber of the heat storage medium cold tank 16 before and after absorbing heat, and the high-grade heat storage medium circulates among the cooler 6, the first high-grade chamber, the heater 11, and the second high-grade chamber. In the heat pump circuit, the high-grade heat storage medium absorbs the high-grade heat energy of the high-temperature CO2 fluid in the cooler 6 and is stored in the first high-grade chamber; in the power generation circuit, the high-grade heat storage medium releases high-grade heat energy in the heater 11, heats the CO2 fluid to a high-temperature state where it can expand and do work, and is then stored in the second high-grade chamber.

[0062] The low-grade heat storage medium is stored in the first low-grade chamber of the heat storage medium hot tank 15 and the second low-grade chamber of the heat storage medium cold tank 16 before and after absorbing heat, and the low-grade heat storage medium circulates among the first multi-stream heat exchanger 4, the first low-grade chamber, the second multi-stream heat exchanger 10, and the second low-grade chamber. In the heat pump circuit, the low-grade heat storage medium absorbs the low-grade heat energy of the CO2 fluid in the first multi-stream heat exchanger 4 and is stored in the first low-grade chamber; in the power generation circuit, the low-grade heat storage medium releases the low-grade heat energy in the second multi-stream heat exchanger 10 to preheat the CO2 fluid and is stored in the second low-grade chamber.

[0063] The cold storage medium is stored in the cold storage medium hot tank 18 and the cold storage medium cold tank 17 before and after absorbing cold energy, and the cold storage medium circulates in the evaporator 3, the cold storage medium cold tank 17, the condenser 14, and the cold storage medium hot tank 18. In the heat pump circuit, the CO2 working medium absorbs heat and evaporates into gas, and the cold storage medium absorbs cold energy and stores it in the cold storage medium cold tank 17; in the power generation circuit, the cold storage medium releases cold energy to cool the CO2 working medium into liquid and then stores it in the cold storage medium hot tank 18.

[0064] In this embodiment, high grade, low grade, high temperature, low temperature, high pressure and low pressure are all relative concepts.

[0065] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A dual liquid storage compressed carbon dioxide energy storage system, characterized in that: include: A heat pump circuit, comprising a low-pressure CO2 liquid storage tank, a throttle valve, an evaporator, a first multi-stream heat regenerator, a compressor and a cooler which are connected in sequence, and the cooler is further connected to a first turbine through the first multi-stream heat regenerator; The power generation circuit includes a high-pressure CO2 liquid storage tank connected to the first turbine, a high-pressure working fluid pump connected to the high-pressure CO2 liquid storage tank in sequence, a second multi-stream heat exchanger, a heater, and a second turbine, and the second turbine is connected to a precooler and a condenser in sequence through the second multi-stream heat exchanger, and the condenser is connected to the low-pressure CO2 liquid storage tank. Among them, CO2 is circulated as a working fluid in the heat pump circuit and the power generation circuit, and low-pressure CO2 liquid is stored in the low-pressure CO2 liquid storage tank. The low-pressure CO2 liquid forms high-pressure CO2 liquid after passing through the heat pump circuit and is stored in the high-pressure CO2 liquid storage tank. The high-pressure CO2 liquid is restored to the low-pressure CO2 liquid after passing through the power generation circuit and is stored in the low-pressure CO2 liquid storage tank.

2. The dual liquid storage compressed carbon dioxide energy storage system according to claim 1, characterized in that: A heat storage circuit is further provided between the cooler, the first multi-stream heat regenerator, the second multi-stream heat regenerator, and the heater. The cooler and the first multi-stream heat regenerator absorb the heat energy of the working fluid in the heat pump circuit and store it in the heat storage circuit, and release the heat energy to the second multi-stream heat regenerator and the heater through the heat storage circuit to heat the working fluid in the power generation circuit. A heat storage medium hot tank and a heat storage medium cold tank are provided in the heat storage circuit, the inlet of the heat storage medium hot tank is communicated with the medium outlet of the cooler and the first multi-stream heat regenerator, the outlet of the heat storage medium hot tank is communicated with the medium inlet of the second multi-stream heat regenerator and the heater, the inlet of the heat storage medium cold tank is communicated with the medium outlet of the second multi-stream heat regenerator and the heater, and the outlet of the heat storage medium cold tank is communicated with the medium inlet of the cooler and the first multi-stream heat regenerator.

3. The dual liquid storage compressed carbon dioxide energy storage system according to claim 2, characterized in that: The heat storage medium hot tank has a first high-grade chamber and a first low-grade chamber which are separated and arranged, and the heat storage medium cold tank has a second high-grade chamber and a second low-grade chamber which are separated and arranged, A high-grade heat storage medium flows through both the cooler and the heater. The high-grade heat storage medium absorbs high-grade thermal energy of the working fluid in the cooler and releases high-grade thermal energy in the heater. The cooler, the first high-grade chamber, the heater, and the second high-grade chamber are sequentially connected to circulate the high-grade heat storage medium.

4. The dual liquid storage compressed carbon dioxide energy storage system according to claim 3, characterized in that: A low-grade heat storage medium flows through both the first multi-stream heat regenerator and the second multi-stream heat regenerator. The low-grade heat storage medium absorbs low-grade heat energy of the working medium in the first multi-stream heat regenerator and releases the low-grade heat energy in the second multi-stream heat regenerator. The first multi-stream heat regenerator, the first low-grade chamber, the second multi-stream heat regenerator, and the second low-grade chamber are sequentially connected to circulate the low-grade heat storage medium.

5. The dual liquid storage compressed carbon dioxide energy storage system according to claim 4, characterized in that: The first multi-stream heat regenerator comprises a first low-temperature working medium flow channel, a first high-temperature working medium flow channel and a second high-temperature working medium flow channel. The inlet of the first low-temperature working medium flow channel is connected to the working medium outlet of the evaporator, the outlet of the first low-temperature working medium flow channel is connected to the working medium inlet of the compressor, and the working medium evaporated by the evaporator flows in the first low-temperature working medium flow channel. The inlets of the first high-temperature working fluid flow channel and the second high-temperature working fluid flow channel are both connected to the working fluid outlet of the cooler, and the outlets of the first high-temperature working fluid flow channel and the second high-temperature working fluid flow channel are both connected to the working fluid inlet of the first turbine. The first high-temperature working fluid flow channel and the second high-temperature working fluid flow channel are both filled with working fluids after high-grade thermal energy has been absorbed. The low-grade heat storage medium absorbs low-grade thermal energy by heat exchange with the first high-temperature working fluid flow channel, and the working fluid in the first low-temperature working fluid flow channel is heat recovered by heat exchange with the second high-temperature working fluid flow channel.

6. The dual liquid storage compressed carbon dioxide energy storage system according to claim 4, characterized in that: The second multi-stream regenerator has a second low-temperature working fluid flow channel and a third high-temperature working fluid flow channel, the inlet of the second low-temperature working fluid flow channel is connected to the working fluid outlet of the high-pressure working fluid pump, the outlet of the second low-temperature working fluid flow channel is connected to the working fluid inlet of the heater, and the working fluid pressurized by the high-pressure working fluid pump flows in the second low-temperature working fluid flow channel. The inlet of the third high-temperature working medium flow passage is communicated with the working medium outlet of the second turbine, and the outlet of the third high-temperature working medium flow passage is communicated with the working medium inlet of the precooler. The working medium with residual heat after expansion and work by the second turbine flows in the third high-temperature working medium flow passage. The working fluid in the second low-temperature working fluid flow channel is preheated by the low-grade thermal energy of the low-grade energy storage medium and the waste heat of the working fluid in the third high-temperature working fluid flow channel.

7. The compressed carbon dioxide energy storage system with dual liquid storage according to claim 1, characterized in that: A cold storage circuit is also provided between the evaporator and the condenser, and the cold energy released by the working fluid in the heat pump circuit is stored in the cold storage circuit, and the working fluid in the power generation circuit is cooled by the stored cold energy. A cold storage medium tank and a hot storage medium tank are provided in the cold storage circuit. Cold storage medium flows through both the evaporator and the condenser. The cold storage medium absorbs cold energy in the evaporator and releases cold energy in the condenser. The evaporator, the cold storage medium tank, the condenser and the hot storage medium tank are connected in sequence to circulate the cold storage medium.

8. The dual liquid storage compressed carbon dioxide energy storage system according to claim 1, characterized in that: The storage pressures of the low-pressure CO2 liquid storage tank and the high-pressure CO2 liquid storage tank are both 1MPa-7.38MPa, the storage temperature of the low-pressure CO2 liquid storage tank is -40℃-5℃, the storage temperature of the high-pressure CO2 liquid storage tank is 30℃, and the low-pressure CO2 liquid in the low-pressure CO2 liquid storage tank and the high-pressure CO2 liquid in the high-pressure CO2 liquid storage tank are both in saturated liquid state.

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