CO2 storage and release method and system for energy storage low-pressure end

Abstract

The invention relates to the field of power engineering and engineering thermophysics, in particular to a CO2 storage and release method and system for an energy storage low-pressure end, and the method adopts a compressed CO2 energy storage cycle, a heat pump loop and a circulating water loop; an alcohol amine solution is used for absorbing CO2 on the low-pressure side, the heat pump loop and the circulating water loop are used for heating and cooling the solution, and then CO2 absorption and release are completed.

Description

Technical Field

[0001] The present invention relates to the fields of power engineering and engineering thermophysics, and in particular to a CO2 storage method and release system for a low-pressure end of compressed CO2 energy storage. Background Art

[0002] With the continuous growth of global energy demand and increasing awareness of environmental protection, energy storage technology has attracted widespread attention as a key means of balancing energy supply and demand and improving energy efficiency. Among the various energy storage technologies, compressed carbon dioxide (CO2) energy storage technology has gradually become a research hotspot due to its high energy storage density and environmental friendliness.

[0003] Currently, compressed CO2 energy storage technology can be divided into three types based on the storage phase of CO2: liquid-liquid compressed CO2 energy storage, gas-liquid compressed CO2 energy storage, and gas-gas compressed CO2 energy storage. When storing CO2, liquid-liquid compressed CO2 energy storage systems occupy relatively little space and have a higher energy storage density because the CO2 is in a liquid state. However, to prevent the liquid CO2 from forming dry ice at low temperatures, the system needs to maintain a low overall pressure, which to some extent limits its energy storage efficiency and the breadth of its application.

[0004] Gas-liquid-compressed CO2 energy storage and gas-gas-compressed CO2 energy storage systems usually use flexible gas storage devices or pressure tanks as CO2 containers on the low-pressure side. Although flexible gas storage devices have a simple structure and low cost, their pressure is at normal pressure, resulting in a large amount of space required to store the same amount of CO2, which is often unacceptable in practical applications. Pressure containers store CO2 through the density difference formed by the sliding pressure on the low-pressure side. Although the space they occupy is usually smaller than that of flexible gas storage devices, they will generate greater energy losses during the sliding pressure process, thereby reducing the energy storage efficiency.

[0005] Chinese patent CN115419484A discloses an energy storage and carbon fixation system for use in the test bench gas cooling process. This system uses a high-temperature gas cooling module to initially cool the gas emitted by the test bench, a cascade energy storage module for secondary cooling and thermal energy storage, a Rankine cycle power generation module to convert thermal energy into electrical energy for storage, and a low-grade gas storage module and a dry ice production module for further processing of the gas and conversion to CO2, respectively. This achieves efficient utilization of waste heat resources and reduction of carbon emissions in the high-altitude simulation test bench for aircraft engines. However, this system mainly focuses on waste heat utilization and CO2 carbon fixation in the test bench gas cooling process, and does not take into account the volume changes of CO2 storage gas. It is insufficient in solving the problem of how to optimize CO2 storage space and efficiency.

[0006] Chinese patent CN115680802A discloses a constant-pressure compressed CO2 energy storage system based on an adsorption method. The system utilizes the principle and characteristics of the material's adsorption and desorption of CO2 to achieve constant-pressure operation of the system, ensuring that the system always operates in a stable operating state during the energy storage and release stages. At the same time, it optimizes the use of adsorption heat, reduces system power consumption, and can be used in conjunction with unstable renewable energy sources such as solar energy and wind energy. It can also be used for peak shaving and valley filling, and no polluting gases are emitted during operation. However, the system mainly focuses on achieving constant-pressure operation, stable operating conditions, and the use of adsorption heat. Although its constant-pressure operation based on the adsorption method may have a certain impact on CO2 storage, it does not directly optimize the volume and energy storage efficiency of the CO2 gas storage reservoir.

[0007] In summary, a method and system for storing and releasing CO2 at the low-pressure end of energy storage is designed, which takes into account storage space volume, system efficiency and economic performance. Summary of the Invention

[0008] The purpose of the present invention is to provide a method and system for storing and releasing CO2 at the low-pressure end of energy storage. This method uses a liquid regulating unit, a CO2 regulating unit and a thermal energy management unit; uses an amine solution to absorb the CO2 on the low-pressure side, and uses the thermal energy management unit and the liquid regulating unit to heat and cool the solution, thereby completing the absorption and release of CO2.

[0009] In order to achieve the above object, the present invention provides the following technical solutions:

[0010] A system for storing and releasing CO2 at the low-pressure end of energy storage, including: a liquid regulating unit, a CO2 regulating unit, and a thermal energy management unit;

[0011] The liquid regulating unit includes a low-temperature storage tank and a high-temperature storage tank. During the energy storage process, the rich liquid enters the high-temperature storage tank, where it is heated to release CO2 and the rich liquid is converted into lean liquid. During the energy release process, the lean liquid enters the low-temperature storage tank, where it is cooled and absorbs CO2 to form rich liquid.

[0012] The CO2 conditioning unit includes a compression-cooling module, a high-pressure storage module, and a heating-expansion module. During energy storage, the compression-cooling module compresses and cools the released CO2, which is then stored in the high-pressure storage module. During energy release, the CO2 in the high-pressure storage module is heated by the heating-expansion module, which then drives the turbine to expand and produce work, and then the CO2 is introduced into the cold water tank of the liquid conditioning unit.

[0013] The thermal energy management unit includes at least one heat source and one cold source, and provides cold energy and heat energy for the energy storage and release processes.

[0014] Furthermore, the absorption liquid in the rich solution and the lean solution is an alcoholamine solution, specifically an ethanolamine (MEA) aqueous solution;

[0015] Furthermore, the mass fraction of the ethanolamine aqueous solution is 10-20%;

[0016] Preferably, the mass fraction of the ethanolamine aqueous solution is 15%.

[0017] Furthermore, in the thermal energy management unit, the heat source includes a hot water tank, a heat pump condenser and a heater, and the cold source includes a cold water tank and a heat exchanger.

[0018] Furthermore, during the energy storage process, when the rich liquid enters the high-temperature storage tank, it exchanges heat with the hot water in the hot water tank. After entering the high-temperature storage tank, the rich liquid is heated by the heat pump condenser and the heater. The hot water is converted into cold water and enters the cold water tank. The cold water provides cold energy for the compression-cooling module, and the cold water is converted into hot water and enters the hot water tank.

[0019] During the energy release process, the hot water in the hot water tank provides thermal energy for the heating-expansion module, which is composed of a multi-stage heater and a turbine in series. The hot water is converted into cold water and enters the cold water tank. The cold water provides cold energy for cooling the lean liquid, and the cold water is converted into hot water and enters the hot water tank.

[0020] Furthermore, the hot water tank is provided with a stirrer for stirring the rich liquid.

[0021] Furthermore, the compression-cooling module in the CO2 regulation unit includes at least one primary compressor and at least one primary cooler, and the compressor and cooler are connected by a pipeline to form a continuous compression-cooling process.

[0022] Furthermore, the high-pressure storage module is equipped with a safety valve and a pressure sensor for monitoring and regulating the storage pressure.

[0023] Furthermore, the multi-stage heater in the heating-expansion module heats the CO2 released from the high-pressure storage module in a gradual heating manner to increase its temperature and pressure, thereby driving the turbine to expand and perform work; the output shaft of the turbine is connected to a generator to convert mechanical energy into electrical energy.

[0024] Furthermore, the heat pump condenser in the thermal energy management unit absorbs ambient heat in the evaporator through the refrigerant and releases heat in the condenser, providing a heat source for heating the rich liquid in the high-temperature storage tank; at the same time, the heat pump condenser is equipped with an expansion valve and a compressor for adjusting the flow and pressure of the refrigerant.

[0025] A method for storing and releasing CO2 at a low-pressure end of an energy storage system comprises the following steps:

[0026] During the energy storage process, the rich liquid in the low-temperature storage tank is transferred to the high-temperature storage tank through a rich liquid pump. The rich liquid is heated, causing CO2 to precipitate from the rich liquid and convert it into lean liquid. The precipitated CO2 is compressed and cooled by the compression-cooling module and then stored in the high-pressure storage module.

[0027] During the energy release process, the CO2 in the high-pressure storage module is heated and expanded by the heating-expansion module, driving the turbine to generate electricity; at the same time, the lean liquid in the high-temperature storage tank is transferred to the low-temperature storage tank through the lean liquid pump. The lean liquid absorbs the expanded CO2 and is converted into rich liquid, completing the energy storage cycle.

[0028] Furthermore, during the energy storage process, the hot water in the hot water tank and the heat pump condenser are used to heat the rich liquid, and the cold water in the cold water tank is used to provide cold energy for compression and cooling;

[0029] and / or;

[0030] During the energy release process, the hot water in the hot water tank is used to provide thermal energy for heating and expansion, and the cold water in the cold water tank is used to provide cold energy for cooling the lean liquid. The cold water is converted into hot water and enters the hot water tank.

[0031] Furthermore, when the hot water in the hot water tank and the heat pump condenser are used to heat the rich liquid, the hot water in the hot water tank is first transported to the heating pipe of the high-temperature storage tank through a water pump to preliminarily preheat the rich liquid before entering the high-temperature storage tank. The rich liquid then enters the high-temperature storage tank and is further heated by the heat pump condenser.

[0032] The present invention also provides a method for storing and releasing CO2 at the low-pressure end of energy storage. The method includes a compressed CO2 energy storage cycle, a heat pump circuit, and a circulating water circuit. The system absorbs the CO2 at the low-pressure end using an amine solution, which is then heated and cooled using the heat pump circuit and circulating water circuit to achieve CO2 absorption and release. The amine solution is an aqueous solution of ethanolamine (MEA) with a mass fraction of 15%.

[0033] During charging, the rich liquid pump draws the rich liquid from the low-temperature alcoholamine storage tank and sprays it into the high-temperature alcoholamine storage tank from above. During the spraying, the rich liquid is heated by hot water from the hot water tank. The hot water provides heat and turns into cold water, which is stored in the cold water tank. The heat pump circuit then continues to heat the rich liquid in the high-temperature alcoholamine storage tank. The agitator at the bottom of the tank stirs the solution to promote heat transfer, thereby precipitating CO2 and converting the rich liquid into lean liquid. During this process, the heat pump circuit stores the resulting cold in the cold water tank. The precipitated CO2 then flows through the compression-cooling module for pressurization before being stored in the high-pressure storage module.

[0034] During discharge, the CO2 in the high-pressure storage module flows into the heating-expansion module, driving the turbine to produce work. Simultaneously, the lean liquid pump draws the lean liquid from the high-temperature amine storage tank. The lean liquid is cooled by cold water in a heat exchanger before entering the low-temperature amine storage tank. The expanded CO2 flows into the low-temperature amine storage tank, where it is absorbed by the lean liquid, converting it into rich liquid. During the absorption process, the reaction heat generated is absorbed by the cold water circulating in the heat pump. A stirrer installed at the bottom of the tank stirs the solution during absorption to promote heat transfer.

[0035] The present invention has the following beneficial effects:

[0036] By utilizing an alcoholamine solution to efficiently absorb and release atmospheric-pressure CO2, this invention effectively reduces the volume of the CO2 storage tank on the low-pressure side of the energy storage system. This improvement addresses the existing problem of low-pressure CO2 storage as atmospheric-pressure gas or in a sliding-pressure manner, requiring significant space, thereby improving the system's space utilization.

[0037] The present invention uses off-peak electricity to drive a heat pump to provide heat for CO2 release during the charging phase, while storing cold energy to provide cold energy for CO2 absorption during the discharge phase. This energy recovery and reuse method reduces energy loss and improves the overall energy storage efficiency of the system.

[0038] By selecting the alcohol amine solution and designing the circulation system, the present invention achieves efficient absorption and release of CO2, reduces the impact of frequent pressure fluctuations on power machinery, and improves the stability and reliability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without inventive work.

[0040] Figure 1 : Compressed CO2 energy storage system based on the coexistence of CO2 reaction heat and compression heat of amine;

[0041] Figure 2 : Compressed CO2 energy storage system based on independent storage of amine CO2 reaction heat and compression heat;

[0042] In the picture:

[0043] 11- low-temperature alcohol amine storage tank, 12- first plug valve, 13- rich liquid pump, 14- second plug valve, 15- high-temperature alcohol amine storage tank, 16- nozzle, 17- first heating pipe, 18- second heating pipe, 19- first motor, 110- first agitator, 111- third plug valve, 112- compression-cooling module, 113- fourth plug valve, 114- high-pressure storage module, 115- fifth plug valve, 116- heating-expansion module, 117- sixth plug valve, 118- seventh plug valve, 119- lean liquid pump, 120- eighth plug valve, 121- heat exchanger, 122- ninth plug valve, 123- cooling pipe, 124- second motor, 125- second agitator;

[0044] 21 - first hot water tank, 22 - tenth stopcock, 23 - first water pump, 24 - eleventh stopcock, 25 - twelfth stopcock, 26 - thirteenth stopcock, 27 - fourteenth stopcock, 28 - first cold water tank, 29 - fifteenth stopcock, 210 - second water pump, 211 - sixteenth stopcock, 212 - cooler, 213 - seventeenth stopcock, 214 - eighteenth stopcock, 215 - nineteenth stopcock, 216 - twentieth stopcock;

[0045] 31-21st plug valve, 32-throttle valve, 33-22nd plug valve, 34-heat pump evaporator, 35-23rd plug valve, 36-compressor, 37-24th plug valve;

[0046] 41 - second hot water tank, 42 - 25th stopcock, 43 - third water pump, 44 - 26th stopcock, 45 - 27th stopcock, 46 - second cold water tank, 47 - 28th stopcock, 48 - fourth water pump, 49 - 29th stopcock, 410 - 30th stopcock;

[0047] 51-the third hot water tank, 52-the third cold water tank. DETAILED DESCRIPTION

[0048] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings 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 making creative efforts shall fall within the scope of protection of the present invention.

[0049] In actual applications, the CO2 storage and release at the low-pressure end of energy storage is composed of a liquid regulating unit, a CO2 regulating unit and a thermal energy management unit. Each unit works together to achieve efficient energy storage and release.

[0050] The liquid conditioning unit includes a low-temperature alcoholamine storage tank and a high-temperature alcoholamine storage tank, which are used to store rich liquid and lean liquid, respectively. During the energy storage process, the rich liquid pump extracts the rich liquid from the low-temperature alcoholamine storage tank and transports it to the high-temperature alcoholamine storage tank through a pipeline. During the transportation process, the rich liquid is first preheated with hot water provided by the hot water tank to improve the heating efficiency after entering the high-temperature alcoholamine storage tank. In the high-temperature alcoholamine storage tank, the rich liquid is further heated by the heat pump condenser and heater, allowing CO2 to be efficiently precipitated from the rich liquid and converted into lean liquid. The precipitated CO2 then enters the compression-cooling module of the CO2 conditioning unit. After multi-stage compression and cooling, it is safely stored in the high-pressure storage module.

[0051] During the energy release process, the high-pressure CO2 in the high-pressure storage module is introduced into the heating-expansion module. After multiple stages of heating and expansion, it drives the turbine to generate power. Simultaneously, a lean liquid pump transfers the lean liquid from the high-temperature amine storage tank to the low-temperature amine storage tank. During this transfer, the lean liquid is cooled by cold water in a heat exchanger to lower its temperature and prepare it for CO2 absorption. The expanded low-pressure CO2 enters the low-temperature amine storage tank, where it is rapidly absorbed by the lean liquid, converting it into rich liquid, completing the CO2 storage process. The heat generated during the absorption process is absorbed by the cold water in the cold water tank, enabling efficient heat recovery and reuse.

[0052] The thermal energy management unit plays a crucial role in the system. It includes a hot water tank, a cold water tank, a heat pump condenser, and a heat exchanger. The hot water tank and cold water tank store hot water and cold water, respectively, providing the necessary heat and cold energy for the energy storage and release processes. The heat pump condenser utilizes the reverse Carnot cycle principle. The refrigerant absorbs ambient heat in the evaporator and releases heat in the condenser, providing an additional heat source for heating the rich liquid in the high-temperature amine storage tank. The heat exchanger cools the lean liquid and recovers heat during the absorption process.

[0053] The system is also equipped with a control unit for real-time monitoring and control of the operating status of each unit. Based on system requirements and external conditions (such as power demand and ambient temperature), the control unit automatically adjusts the flow rates of the rich and lean liquid pumps, the operating parameters of the heat pump condenser and heater, and the working status of the compression-cooling module and heating-expansion module, ensuring stable system operation and efficient energy storage. The control unit also features fault self-detection and alarm functions. Upon detecting an abnormality, it immediately initiates appropriate protective measures to ensure system safety and reliability.

[0054] Through the above specific implementation methods, the CO2 storage and release system for the low-pressure end of energy storage of the present application can significantly reduce the storage volume, improve energy storage efficiency, enhance system stability, and has good economic performance and environmental benefits.

[0055] During the energy storage process, the rich liquid in the low-temperature alcoholamine storage tank 11 flows sequentially through the first stopcock 12, the rich liquid pump 13, and the second stopcock 14 before entering the high-temperature alcoholamine storage tank 15. Upon entering the tank, it is sprayed down from the nozzle 16 above the tank. During the spraying process, it is heated by the first heating tube 17 and then further heated by the second heating tube 18, thereby precipitating CO2 and turning the solution into a lean solution. Simultaneously, the first motor 19 drives the first agitator 110 to stir the solution to ensure sufficient heat transfer. The precipitated CO2 flows through the third stopcock 111 into the compression-cooling module 112. After pressurization, the high-pressure CO2 flows through the fourth stopcock 113 and is stored in the high-pressure storage module 114. In the above process, the heat for heating pipe 17 comes from hot water. The hot water in first hot water tank 21 (or third hot water tank 51) flows through tenth stopcock 22, first water pump 23, eleventh stopcock 24, and twelfth stopcock 25, heating the amine solution in heating pipe 17 before becoming cold water and flowing through thirteenth stopcock 26 into first cold water tank 28. The heat for heating pipe 18 comes from the heat pump circuit. The heat pump working fluid flows through twenty-first stopcock 31, where its pressure is reduced in throttle valve 32. It then flows through twenty-second stopcock 33 and enters heat pump evaporator 34, where it is heated. It then passes through twenty-third stopcock 35, is compressed by compressor 36, and flows through twenty-fourth stopcock 35 into heating pipe 18 to heat the solution. The heat provided by heat pump evaporator 34 comes from second hot water tank 41. The hot water in the second hot water tank 41 flows through the twenty-fifth stopcock 42, the third water pump 43, and the twenty-sixth stopcock 44 to enter the heat pump evaporator 34 to provide heat. It then becomes cold water and passes through the twenty-seventh stopcock 44 to be stored in the second cold water tank 46. Furthermore, after the CO2 is compressed, the cold water in the first cold water tank 28 flows through the fifteenth stopcock 29, the second water pump 210, the sixteenth stopcock 211, the cooler 212, and the seventeenth stopcock 213 before entering the compression cooling module to cool the CO2. It then becomes hot water and flows through the eighteenth stopcock 214 into the first hot water tank 21.

[0056] During the energy release process, the high-pressure CO₂ in the high-pressure storage module 114 flows through the fifth rotary valve 115, drives the turbine in the heating-expansion module 116 to generate electricity, and then flows through the sixth rotary valve 117 to enter the low-temperature amine storage tank 11. Simultaneously, the lean liquid in the high-temperature amine storage tank 15 passes through the seventh rotary valve 118, pump 119, and eighth rotary valve 120, is cooled in the heat exchanger 121, and then flows through the ninth rotary valve 122 into the low-temperature amine storage tank 11. The lean liquid in the tank begins to absorb the CO₂, and the heat released is removed by the cooling pipe 123. Simultaneously, the second motor 124 drives the stirrer 125 to stir the solution to ensure efficient heat transfer. During this process, the cold water in the heat exchanger 121 comes from the first cold water tank 28. The cold water in the first cold water tank 28 passes through the 15th stopcock 29, the second water pump 210, the 16th stopcock 211, the cooler 212, the 17th stopcock 213, and the 19th stopcock 215, then enters the heat exchanger 121. After cooling, the cold water becomes hot water and flows through the 20th stopcock 216 into the first hot water tank 21. Furthermore, the heat required for the CO2 in the heating-expansion module is provided by the first hot water tank 21. Hot water flows from the first hot water tank 21, passes through the 10th stopcock 22, the first water pump 23, and the 11th stopcock 24, and then enters the heating-expansion module 116 to heat the CO2. After heating, the hot water becomes cold water and flows through the 14th stopcock 27, where it is stored in the first cold water tank 28. Meanwhile, the heat generated by the mixing of the amine solution and CO2 is absorbed by the cold water from the second cold water tank 46. The cold water in the second cold water tank 46 flows through the twenty-eighth stopcock 47, the fourth water pump 48, the twenty-ninth stopcock 49 in sequence, and then flows into the cooling pipe 123. After cooling, it becomes hot water, flows through the thirtieth stopcock 410 and is stored in the second hot water tank 41.

[0057] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the systems shown in the accompanying drawings.

[0058] Example 1:

[0059] The connection diagram of the circulation system in this example is as follows: Figure 1 shown.

[0060] The present invention provides a method for storing and releasing CO2 at the low-pressure end of an energy storage system, including the following two operating modes:

[0061] Mode 1: Energy storage process, low-pressure CO2 is precipitated from the amine solution and completes the compression and cooling process.

[0062] Mode 2: Energy release process, high-pressure CO2 is absorbed by the amine solution after completing the heating and expansion process.

[0063] Mode 1

[0064] In mode one, the rich liquid in the low-temperature alcoholamine storage tank 11 is pumped out by the rich liquid pump 13 and flows into the high-temperature alcoholamine storage tank 15. The rich liquid is sprayed into the tank through the nozzle 16 and is heated by the heating pipe 17 during spraying. The heat of the heating pipe 17 comes from the first hot water tank 21. After providing heat, the hot water becomes cold water and is stored in the first cold water tank 28. The solution entering the tank is continuously heated by the heating pipe 18, CO2 is precipitated and becomes a lean liquid. During this process, the first motor 19 drives the first agitator 110 to stir the solution and promote heat transfer. The heat of the heat pipe 18 comes from the heat pump circuit. The heat pump solution drops pressure through the throttle valve 32, absorbs heat in the heat pump evaporator 34, and is pressurized in the compressor 36. It then enters the high-temperature alcoholamine storage tank 11 to heat the solution. The heat provided by the heat pump evaporator 34 comes from the second hot water tank 41. The hot water in the second hot water tank 41 is pumped by the third water pump 43 and then enters the heat pump evaporator 34 to heat the heat pump working fluid. It is then converted into cold water and stored in the cold water tank 40. The CO2 separated from the high-temperature amine storage tank 11 flows into the compression-cooling module 112 for pressurization. The high-pressure CO2 is then stored in the high-pressure storage module 114. The cold water required by the compression-cooling module 114 is provided by the first cold water tank 28. After cooling the CO2, the cold water is converted into hot water and stored in the first hot water tank 21.

[0065] Mode 2

[0066] In mode 2, the lean liquid from the high-temperature amine solution storage tank 15 is pumped out by pump 119 and then cooled in heat exchanger 121 by cold water from the outlet of cooler 212 before entering the low-temperature amine storage tank 11. After cooling the lean liquid, the cold water becomes hot water, which is stored in the third hot water tank 51. Simultaneously, high-pressure CO₂ flows from the high-pressure storage module 114 and enters the heating-expansion module 116. The hot water required for the heating-expansion module 116 is provided by the third hot water tank 51. After heating the CO₂, the hot water becomes cold water, which is stored in the first cold water tank 28. After the expansion process is complete, the low-pressure CO₂ flows into the low-temperature amine storage tank 11 and is absorbed by the lean liquid. After absorbing the CO₂, the lean liquid in the low-temperature amine storage tank 11 becomes rich liquid and releases heat. During the absorption process, the second motor 124 drives the stirrer 125 to stir the solution, promoting heat exchange. The heat generated during the absorption process is absorbed by the cold water in the second cold water tank 46. After absorbing the heat, the cold water becomes hot water, which is stored in the second hot water tank 41.

[0067] Example 2:

[0068] The connection diagram of the circulation system in this example is as follows: Figure 2 As shown, the difference between Example 2 and Example 1 is that the reaction heat and the compression heat do not need to coexist.

[0069] Mode 1: Energy storage process, low-pressure CO2 is precipitated from the amine solution and completes the compression and cooling process.

[0070] Mode 2: Energy release process, high-pressure CO2 is absorbed by the amine solution after completing the heating and expansion process.

[0071] Mode 1

[0072] In mode one, the rich liquid in the low-temperature alcoholamine storage tank 11 is pumped out by the rich liquid pump 13 and flows into the high-temperature alcoholamine storage tank 15. The rich liquid is sprayed into the tank through the nozzle 16 and is heated by the heating pipe 17 during the spraying. The heat of the heating pipe 17 comes from the third hot water tank 51. After providing heat, the hot water becomes cold water and is stored in the third cold water tank 52. The solution entering the tank is continuously heated by the heating pipe 18, CO2 is precipitated and becomes a lean liquid. During this process, the first motor 19 drives the first agitator 110 to stir the solution and promote heat transfer. The heat of the heat pipe 18 comes from the heat pump circuit. The heat pump solution drops pressure through the throttle valve 32, absorbs heat in the heat pump evaporator 34, and is pressurized in the compressor 36. It then enters the high-temperature alcoholamine storage tank 11 to heat the solution. The heat provided by the heat pump evaporator 34 comes from the second hot water tank 41. The hot water in the second hot water tank 41 is pumped by the third water pump 43 and then enters the heat pump evaporator 34 to heat the heat pump working fluid. It is then converted into cold water and stored in the cold water tank 40. The CO2 separated from the high-temperature amine storage tank 11 flows into the compression-cooling module 112 for pressurization. The high-pressure CO2 is then stored in the high-pressure storage module 114. The cold water required by the compression-cooling module 114 is provided by the third cold water tank 52. After cooling the CO2, the cold water is converted into hot water and stored in the third hot water tank 51.

[0073] Mode 2

[0074] In mode 2, the lean liquid from the high-temperature amine solution storage tank 15 is pumped out by pump 119 and then cooled in heat exchanger 121 by cold water from the outlet of cooler 212 before entering the low-temperature amine storage tank 11. The cold water cools the lean liquid and turns into hot water, which is stored in the third hot water tank 51. Simultaneously, high-pressure CO₂ flows from the high-pressure storage module 114 and enters the heating-expansion module 116. The hot water required for the heating-expansion module 116 is provided by the third hot water tank 51. After heating the CO₂, the hot water turns into cold water, which is stored in the third cold water tank 52. After the expansion process is complete, the low-pressure CO₂ flows into the low-temperature amine storage tank 11 and is absorbed by the lean liquid. After absorbing the CO₂, the lean liquid in the low-temperature amine storage tank 11 becomes rich liquid and releases heat. During the absorption process, the second motor 124 drives the stirrer 125 to stir the solution, promoting heat exchange. The heat generated during the absorption process is absorbed by the cold water in the second cold water tank 46. After absorbing the heat, the cold water turns into hot water, which is stored in the second hot water tank 41.

Claims

1. A system for storing and releasing CO2 at the low-pressure end of energy storage, characterized in that: The system includes: a liquid regulating unit, a CO2 regulating unit and a thermal energy management unit; Liquid conditioning unit, including low-temperature storage tank and high-temperature storage tank; The CO2 regulation unit includes a compression-cooling module, a high-pressure storage module, and a heating-expansion module. During the energy storage process, the compression-cooling module compresses and cools the precipitated CO2 and stores it in the high-pressure storage module. During the energy release process, the CO2 in the high-pressure storage module is heated by the heating-expansion module, which drives the turbine to expand and perform work, and then the CO2 is introduced into the liquid regulation unit. The thermal energy management unit includes at least one heat source and at least one cold source.

2. The system according to claim 1, wherein: In the thermal energy management unit, the heat source includes a hot water tank, a heat pump condenser and a heater, and the cold source includes a cold water tank and a heat exchanger.

3. The system according to claim 2, characterized in that The heating-expansion module is composed of a multi-stage heater and a turbine connected in series.

4. The system according to claim 2, wherein: The hot water tank is provided with a stirrer.

5. The system according to claim 1, wherein: The compression-cooling module in the CO2 regulation unit includes at least one primary compressor and at least one primary cooler. The compressor and the cooler are connected by a pipeline to form a continuous compression-cooling process.

6. The system according to claim 1, wherein: The high-pressure storage module is equipped with a safety valve and a pressure sensor for monitoring and regulating the storage pressure.

7. The system according to claim 1, wherein: The multi-stage heater in the heating-expansion module heats the CO2 released from the high-pressure storage module in a gradual heating manner to increase its temperature and pressure, thereby driving the turbine to expand and perform work; the output shaft of the turbine is connected to a generator to convert mechanical energy into electrical energy.

8. The system according to claim 1, wherein: The heat pump condenser in the thermal energy management unit absorbs ambient heat in the evaporator through the refrigerant and releases heat in the condenser, providing a heat source for heating the rich liquid in the high-temperature storage tank; at the same time, the heat pump condenser is equipped with an expansion valve and a compressor for adjusting the flow and pressure of the refrigerant.

9. A method for storing and releasing CO2 at a low-pressure end of energy storage, characterized in that: The method is implemented using the system according to any one of claims 1 to 8, comprising the following steps: During the energy storage process, the rich liquid in the low-temperature storage tank is transferred to the high-temperature storage tank through a rich liquid pump. The rich liquid is heated, causing CO2 to precipitate from the rich liquid and convert it into lean liquid. The precipitated CO2 is compressed and cooled by the compression-cooling module and then stored in the high-pressure storage module. During the energy release process, the CO2 in the high-pressure storage module is heated and expanded by the heating-expansion module, driving the turbine to generate electricity; at the same time, the lean liquid in the high-temperature storage tank is transferred to the low-temperature storage tank through the lean liquid pump. The lean liquid absorbs the expanded CO2 and is converted into rich liquid, completing the energy storage cycle.

10. The method according to claim 9, characterized in that During the energy storage process, the hot water in the hot water tank and the heat pump condenser are used to heat the rich liquid, and the cold water in the cold water tank is used to provide cold energy for compression and cooling; and / or; During the energy release process, the hot water in the hot water tank is used to provide thermal energy for heating and expansion, and the cold water in the cold water tank is used to provide cold energy for cooling the lean liquid. The cold water is converted into hot water and enters the hot water tank.

11. The method according to claim 10, characterized in that When the hot water in the hot water tank and the heat pump condenser are used to heat the rich liquid, the hot water in the hot water tank is first transported to the heating pipe of the high-temperature storage tank through a water pump to preliminarily preheat the rich liquid before entering the high-temperature storage tank. The rich liquid then enters the high-temperature storage tank and is further heated by the heat pump condenser.

12. The method according to claim 9, characterized in that The absorption liquid in the rich solution and the lean solution is an alcoholamine solution.

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