Hot-water-supplementing-free hydraulic compressed carbon dioxide energy storage system and energy charging and discharging circulation method

Abstract

The invention provides a heat-supplementing-free hydraulic compression carbon dioxide energy storage system and an energy charging and discharging circulating method.The energy charging and discharging circulating method comprises the steps that in the energy storage process, gaseous carbon dioxide is firstly subjected to adiabatic compression and then subjected to isothermal compression to obtain saturated liquid carbon dioxide, and in the energy discharging process, the liquid carbon dioxide is firstly subjected to adiabatic expansion and then subjected to isothermal compression to obtain saturated liquid carbon dioxide; isothermal expansion pushes a water impact turbine to do work for power generation; according to the characteristics of hydraulic compression carbon dioxide energy storage, an adiabatic compression-isothermal compression-adiabatic expansion-isothermal expansion energy charging and releasing thermodynamic process is provided, waste heat released in the energy storage process is fully utilized, and the circulation efficiency of the system is improved; the invention provides a double-loop control system for controlling the circulating water flow through carbon dioxide temperature feedback and controlling the power of a water feeding pump / a water turbine through carbon dioxide pressure feedback, and it is guaranteed that the actual circulating process can be conducted according to a design curve; through thermodynamic optimization of the energy charging and releasing process, heat in the energy storage process can be fully recycled, and external heat compensation is not needed.

Description

Technical Field

[0001] This invention belongs to the field of compressed gas energy storage technology, specifically relating to a hydraulically compressed carbon dioxide energy storage system without hot water replenishment and a charging and discharging cycle method. Background Technology

[0002] Compressed air energy storage technology occupies an important position in power systems due to its large-scale energy storage capacity and flexible peak-shaving capabilities. However, its inherent low energy density and high dependence on specific geological conditions significantly limit its application scope. Further exploration has revealed that while liquefied air energy storage can significantly increase energy density through phase change, the large input work required for the liquefaction process leads to low system efficiency, and the complex configuration of heating and cooling networks significantly increases engineering costs.

[0003] In contrast, liquid carbon dioxide energy storage technology exhibits unique advantages: CO2 can be liquefied at room temperature and high pressure, without the need for extreme low-temperature environments, and the dual-phase liquid storage mode can avoid the uneven heat and mass transfer problems of traditional gas-liquid two-phase flow. The system's structural compactness is improved by about 30%-50% compared to conventional compressed air energy storage. However, existing technologies still face key challenges: the low-pressure side CO2 compression needs to be maintained below -20°C, and the forced refrigeration system consumes additional energy storage capacity; at the same time, the design of independent liquid storage tanks on the high and low pressure sides increases equipment redundancy, resulting in higher life-cycle costs than traditional solutions.

[0004] Patent CN120062847A discloses a marine constant-pressure compressed carbon dioxide energy storage system coupled with ocean temperature difference, including a constant-pressure working fluid storage device, a carbon dioxide energy storage loop, a carbon dioxide energy release loop, and a thermal storage loop. In the energy storage stage, deep-sea low-temperature seawater is used to condense gaseous carbon dioxide into liquid, and in the energy release stage, shallow-sea high-temperature seawater is used to evaporate liquid carbon dioxide into gas, fully utilizing marine renewable energy and ocean temperature difference to achieve gas-liquid conversion of carbon dioxide. A flexible constant-pressure working fluid storage device is used to store low-pressure gaseous and high-pressure liquid carbon dioxide, ensuring constant pressure during charging and discharging, achieving efficient and stable system operation. Power is generated by using the carbon dioxide expansion process to drive an expander, utilizing ocean temperature difference and seawater static pressure to achieve efficient liquefaction and high-density storage of high-pressure carbon dioxide, improving the efficiency and energy density of the energy storage system. Patent CN118934389A discloses a hydraulic compressed gas energy storage system and method with supplemental heating for carbon dioxide. The system includes a water storage container containing a flexible container. The water storage container is connected to a water pump and turbine via inlet and outlet pipes. The drive shaft of the water pump and turbine is connected to the rotating shaft of a generator motor via a transmission device. The flexible container is connected to a liquid carbon dioxide storage container via a first valve, both the first valve and the liquid carbon dioxide storage container being located outside the water storage container. The patent focuses on the composition of the compressed carbon dioxide energy storage system, the connection methods of its components, and its basic operating method, but does not mention how to improve the cycle efficiency of the energy storage system by optimizing the charge-discharge cycle strategy.

[0005] In recent years, hydraulic compression carbon dioxide energy storage systems have innovatively coupled hydraulic potential energy with the CO2 compression process, simplifying core equipment configuration and significantly improving theoretical energy efficiency. However, their thermal management mechanism has fundamental flaws: waste heat generated during compression is not effectively recovered, and heat absorption during expansion exacerbates energy loss, resulting in actual cycle efficiency often lower than theoretical values. Furthermore, existing heat exchangers struggle to achieve efficient cross-medium heat exchange between CO2 and water, further hindering system performance optimization. Therefore, constructing a multi-energy-flow-coordinated heat storage and release system has become a key bottleneck in the engineering of this technology. This application is proposed to address the problem of efficient energy charging and releasing in hydraulic compression carbon dioxide energy storage systems. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a non-compensated hot water hydraulic compression carbon dioxide energy storage system and a charge-release cycle method. Under conditions of no external heat replenishment, by optimizing the thermodynamics of the charge-release process, the heat of the energy storage process can be fully recovered and utilized without external heat replenishment, making it suitable for scenarios where there is no external residual heat. At the same time, it maximizes the system's cycle efficiency, with a theoretical thermodynamic cycle efficiency of over 90%.

[0007] To achieve the above objectives, on the one hand, the present invention provides a hydraulically compressed carbon dioxide energy storage system without hot water supply, including a heat exchanger, a gas storage tank, an electric motor, a generator, a water pump, a water turbine, and a water storage tank; a compressible expansion space is provided in the gas storage tank, and carbon dioxide is filled between the gas storage tank and the compressible expansion space; the compressible expansion space is connected to the water storage tank via the water pump or the water turbine; a heat exchange space is provided on the outside of the gas storage tank, and the heat exchange space is connected to the first heat exchange side of the heat exchanger; the second heat exchange side of the heat exchanger is connected to a water source; and the water turbine is connected to the generator.

[0008] Furthermore, the water pump and turbine are water pump turbines, and the generator and motor are electric generators.

[0009] Furthermore, a heat insulation layer is installed on the outside of the heat exchange space on the gas storage tank, and pressure and temperature sensors are installed inside the gas storage tank.

[0010] Furthermore, a water storage tank is connected to the second heat exchange side of the heat exchanger, a variable frequency pump is used for the water supply pump, and a circulation pump is installed on both pipelines of the heat exchanger.

[0011] Furthermore, a shell is provided on the outer side of the upper part of the gas storage tank and is sealed relative to the tank wall to form a heat exchange space, and enhanced heat exchange fins are provided in the heat exchange space.

[0012] On the other hand, the present invention provides a charging and releasing cycle method for a hydraulically compressed carbon dioxide energy storage system without replenishment water. During the energy storage process, gaseous carbon dioxide is first adiabatically compressed and then isothermally compressed to saturated liquid carbon dioxide. During the energy release process, liquid carbon dioxide is first adiabatically expanded and then isothermally expanded to drive water to impact a water turbine to generate electricity.

[0013] Furthermore, during the energy storage process, in the initial state, the temperature of gaseous carbon dioxide is 20~25℃ and the pressure is 5.0~5.2MPa. After adiabatic compression, the temperature of carbon dioxide is 30~35℃ and the pressure is 5.5~5.7MPa. It is then isothermally compressed to a liquid state with a temperature of 30~35℃ and a pressure of 6.5~6.7MPa.

[0014] Furthermore, during the energy release process, carbon dioxide first expands adiabatically from a temperature of 30~35℃ and a pressure of 6.5~6.7MPa to a temperature of 20~25℃ and a pressure of 5.6~5.8MPa, and then expands isothermally to a temperature of 20~25℃ and a pressure of 5.0~5.2MPa.

[0015] Furthermore, during the energy storage process, water is used to exchange heat with carbon dioxide, raising the water temperature from 25°C to 35°C, and the heated water is stored in a storage tank; during the energy release process, the water exchanges heat with carbon dioxide, lowering the temperature from 35°C to 25°C, and is then stored.

[0016] Furthermore, the temperature and pressure of carbon dioxide are monitored, the temperature signal of carbon dioxide is obtained and the difference between the temperature and the target temperature is obtained, and the water flow rate for heat exchange with carbon dioxide is adjusted by PID control. The pressure of carbon dioxide is obtained and the pressure difference between the pressure and the target pressure is obtained, and the power of the pressurization device is adjusted by PID control.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects: This invention addresses the characteristics of hydrodynamic compression carbon dioxide energy storage by proposing a thermodynamic process of energy release involving adiabatic compression-isothermal compression-adiabatic expansion-isothermal expansion. This process fully utilizes the waste heat released during the energy storage process and improves the system's cycle efficiency. This invention proposes a dual-loop control system that uses carbon dioxide temperature feedback to control the circulating water flow rate and carbon dioxide pressure feedback to control the power of the feedwater pump / turbine, ensuring that the actual circulation process can proceed according to the design curve. Under conditions of no external heat replenishment, by optimizing the thermodynamics of the energy charging and releasing process, the heat of the energy storage process can be fully recovered and utilized without external heat replenishment, making it suitable for scenarios where there is no external residual heat; at the same time, the system's cycle efficiency is maximized, with a theoretical thermodynamic cycle efficiency of over 90%.

[0018] Furthermore, the system described in this application achieves a cycle of carbon dioxide compression energy storage and expansion energy release through the synergistic action of a heat exchanger, a gas storage tank, a feedwater pump, a water turbine, and a water storage tank, without the need for external heat replenishment. During the energy charging stage, the electric motor drives the feedwater pump to pressurize water into the compressible expansion space, compressing the carbon dioxide for energy storage. At the same time, the heat of compression is transferred to the second heat exchange side through the heat exchanger, reducing heat loss. During the energy release stage, the high-pressure carbon dioxide expands to drive the water turbine to generate electricity. The heat exchanger absorbs heat from the water source to maintain the operating temperature of the carbon dioxide, avoiding efficiency reduction caused by low temperature.

[0019] Furthermore, the compressible expansion space inside the gas storage tank comes into direct contact with carbon dioxide, simplifying the structure and improving the response speed.

[0020] Furthermore, the water pump turbine and electric generator reduce the investment in large equipment, reduce the footprint and initial investment, and reduce energy loss and equipment complexity; the integrated design reduces the number of components, improves system reliability, and is suitable for frequent charging and discharging scenarios.

[0021] Furthermore, the insulation layer reduces heat exchange between the gas storage tank and the outside environment, maintains the stability of the carbon dioxide operating temperature, and avoids the impact of ambient temperature fluctuations on system efficiency; pressure / temperature sensors monitor the status of the gas storage tank in real time, providing data support for system regulation and ensuring safe operation.

[0022] Furthermore, the water storage tank serves as a heat buffer unit on the second heat exchange side, balancing fluctuations in the water source temperature and improving the efficiency of the heat exchanger.

[0023] Furthermore, the variable frequency pump adjusts the water flow rate according to the load demand, optimizes energy consumption, and improves the feasibility of fine control of the overall system. At the same time, the circulating pump enhances the fluid circulation in the heat exchange pipeline, avoids local overheating / overcooling, and improves the uniformity of heat exchange.

[0024] Furthermore, the sealed heat exchange space is formed by the shell and the upper part of the gas storage tank, which allows for precise management of the heat exchange process and reduces heat leakage.

[0025] Furthermore, strengthening the fins increases the heat exchange area, accelerates the heat transfer efficiency between carbon dioxide and water, and shortens the charging and discharging cycle. Attached Figure Description

[0026] Figure 1 This is a temperature-entropy diagram of the energy release process.

[0027] Figure 2 The temperature change curve of the working fluid during the energy release process.

[0028] Figure 3 The pressure and temperature change curves for the energy release process.

[0029] Figure 4 It is a carbon dioxide energy storage system without hot water replenishment.

[0030] Figure 5 This is a schematic diagram of a hydraulically compressed carbon dioxide energy storage system without a water tank or replenishment water.

[0031] In the attached diagram, 1-heat exchanger, 2-air tank, 3-generator, 4-water turbine, 5-water reservoir, 6-water tank, 7-compressible expansion structure. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Example 1, Reference Figure 1 , Figure 2 and Figure 3This invention provides a method for the charge-release cycle of a hydraulically compressed carbon dioxide energy storage system without replenishment water. The method includes an energy storage process and an energy release process. During the energy storage process, gaseous carbon dioxide is first adiabatically compressed, then isothermally compressed to saturated liquid carbon dioxide. Initially, the gaseous carbon dioxide has a temperature of 20-25°C and a pressure of 5.0-5.2 MPa. After adiabatically compressed, the carbon dioxide temperature is 30-35°C and the pressure is 5.5-5.7 MPa. It is then isothermally compressed further to a liquid state with a temperature of 30-35°C and a pressure of 6.5-6.7 MPa. Water is used for heat exchange with the carbon dioxide, raising the water temperature from 25°C to 35°C. This heated water is then stored in a water storage tank 6.

[0034] During the energy release process, liquid carbon dioxide first undergoes adiabatic expansion, then isothermal expansion, driving water to impact a turbine and generate electricity. The carbon dioxide expands adiabatically from a temperature of 30-35℃ and a pressure of 6.5-6.7 MPa to a temperature of 20-25℃ and a pressure of 5.6-5.8 MPa, then isothermally expands to 20-25℃ and a pressure of 5.0-5.2 MPa. Water, after exchanging heat with the carbon dioxide, cools from 35℃ to 25℃ and is then stored.

[0035] refer to Figure 1 , Figure 2 , Figure 3 This invention employs adiabatic compression followed by isothermal compression during energy storage. The first stage uses adiabatic compression, which, with the same work input from the pump, raises the working fluid temperature to its maximum. This maximizes the temperature of the circulating cooling water. Since the circulating cooling water acts as a heat source during the heat release phase, a higher temperature results in higher system circulation efficiency. The second stage uses isothermal compression, which liquefies the gaseous carbon dioxide working fluid and maintains it at a high temperature throughout the compression process. In the energy release phase, adiabatic expansion is employed first, followed by isothermal expansion. Adiabatic expansion in the first stage minimizes the working fluid temperature while maximizing the work output during expansion. This results in the largest temperature difference between the liquid carbon dioxide and the circulating water, significantly reducing the heat exchange area and lowering the cost of the spiral tube. Isothermal expansion in the second stage vaporizes the liquid carbon dioxide working fluid and maintains it at a low temperature throughout the expansion process.

[0036] Throughout the process, the temperature and pressure of carbon dioxide are monitored, the temperature signal of carbon dioxide is obtained and the difference between the temperature and the target temperature is obtained, and the water flow rate for heat exchange with carbon dioxide is adjusted by PID control. The pressure of carbon dioxide is obtained and the pressure difference between the pressure and the target pressure is obtained, and the power of the pressurization device is adjusted by PID control.

[0037] In a hydraulically compressed carbon dioxide energy storage system without hot water replenishment, the temperature and pressure of carbon dioxide directly affect the efficiency of energy storage and release, as well as the system's safety. Real-time monitoring and automatic adjustment ensure stable system operation. The system monitors the temperature and pressure of carbon dioxide in real time. Temperature sensors continuously measure the temperature of the carbon dioxide inside the storage tank and feed the data back to the control system; pressure sensors detect the pressure of the carbon dioxide inside the storage tank in real time and transmit the data to the control unit.

[0038] Set the target temperature and target pressure for carbon dioxide based on the current energy charge or release of the system.

[0039] The control system compares the current carbon dioxide temperature with the target temperature to determine whether heating or cooling is necessary. If the temperature exceeds the target value, the control system automatically increases the water flow rate in the heat exchanger to accelerate heat exchange and cool the carbon dioxide.

[0040] If the temperature is lower than the target value, the control system reduces the water flow to slow down heat loss and help the carbon dioxide heat up. By dynamically adjusting the water flow, the temperature of the carbon dioxide is always maintained within the optimal operating range, avoiding the impact on system performance due to excessively high (efficiency) or excessively low temperatures.

[0041] The control system compares the current carbon dioxide pressure with the target pressure to determine whether pressurization or depressurization is needed. If the pressure is lower than the target value, the control system increases the power of the water pump or compressor to increase the compression of carbon dioxide and raise its pressure.

[0042] If the pressure exceeds the target value, the control system reduces the power of the pressurization device or switches to the energy release mode to reduce the pressure, ensuring that the pressure in the gas storage tank is always within a safe and efficient range, thereby improving equipment utilization and overall system efficiency.

[0043] Pressure control usually takes precedence over temperature control, as excessive pressure may directly threaten system safety.

[0044] As an example, during the charging phase, the compression of carbon dioxide causes the temperature to rise. At this time, the system will simultaneously increase the water flow to cool down and prevent overheating. Even if the external environment changes, the control system can still automatically adjust to maintain stable operation. Through precise control, it ensures that the carbon dioxide is always in the best working condition.

[0045] refer to Figure 5Example 2, based on the energy storage and charging cycle method of the hydraulically compressed carbon dioxide energy storage system without replenishment water provided in Example 1, provides a hydraulically compressed carbon dioxide energy storage system without replenishment water, including a heat exchanger 1, a gas storage tank 2, an electric motor, a generator 3, a water pump, a water turbine 4, and a water storage tank 5; a compressible expansion space 7 is provided in the gas storage tank 2, and carbon dioxide is filled between the gas storage tank 2 and the compressible expansion space 7. The compressible expansion space 7 is connected to the water storage tank 5 via the water pump or the water turbine 4. A heat exchange space is provided on the outside of the gas storage tank 2, and the heat exchange space is connected to the first heat exchange side of the heat exchanger 1. The second heat exchange side of the heat exchanger 1 is connected to a water source, and the water turbine 4 is connected to the generator.

[0046] As a preferred embodiment, the water pump and water turbine 4 are water pump-water turbines, and the generator 3 and electric motor are electric generators, which reduces the overall footprint and lowers equipment investment.

[0047] A heat insulation layer is installed on the outside of the heat exchange space of the gas storage tank 2 to improve the efficiency of the working fluid and the accuracy of temperature control. Pressure sensors and temperature sensors are installed in the gas storage tank 2 to monitor the temperature and pressure of the working fluid in real time, so as to facilitate parameter adjustment.

[0048] Bypass pipes are provided at the inlet and outlet of the water pump and turbine 4, and valves are installed on the bypass pipes. In a hydraulically compressed carbon dioxide energy storage system without hot water replenishment, the design of providing bypass pipes and valves at the inlet and outlet of the water pump and turbine can significantly improve the system's flexibility, safety, and operating efficiency.

[0049] During initial system operation, water can bypass the feedwater pump or turbine via a bypass pipeline to prevent equipment from starting under high pressure differential and reduce mechanical shock. For example, before charging, the bypass valve can be briefly opened to allow water to slowly fill the pipeline and balance the pressure before starting the feedwater pump. When the system is shut down, the bypass pipeline can slowly release residual pressure in the pipeline to avoid water hammer.

[0050] By switching the status of the bypass valve, the water flow path can be quickly adjusted. For example, when charging, the turbine bypass valve is closed, and the water flows through the feedwater pump to compress CO2 for energy storage; when releasing energy, the feedwater pump bypass valve is closed, and the water flows through the turbine to generate electricity.

[0051] If the feedwater pump or turbine fails, the bypass valve can be opened immediately to maintain some functions of the system, avoid a complete shutdown, improve the system response speed, and ensure continuous operation.

[0052] When there is low load demand, some water flow can be diverted through bypass valves to reduce the work done by the feedwater pumps or turbines and avoid the equipment operating in an inefficient range. During the energy release process, if the turbine generates excess power, the bypass valves can be opened to divert the excess water flow to balance the demand of power generation and the power grid. This improves the system efficiency under partial load and reduces energy waste.

[0053] When the pipeline pressure rises abnormally, the bypass valve can automatically open to relieve pressure and prevent equipment or gas storage tank from overloading. When repairing the feedwater pump or turbine, closing the inlet and outlet valves and opening the bypass can isolate the equipment without affecting other parts of the system.

[0054] The bypass pipeline can be linked with the PID control system. For example, if the CO2 temperature is too high, the bypass valve can help adjust the water flow rate and work with the heat exchanger to cool it down quickly.

[0055] As a possibility, when multiple feedwater pumps / turbines are operating in parallel, bypass piping can be used to balance the flow distribution among the equipment.

[0056] The water supply pump is a variable frequency pump, which can better couple power changes. Circulation pumps are installed on both pipelines of heat exchanger 1 to effectively improve the working efficiency and working range of heat exchanger 1.

[0057] The upper half of the gas storage tank 2 is provided with a shell on the outside and is sealed relative to the tank wall to form a heat exchange space. The heat exchange space is provided with reinforced heat exchange fins to improve heat exchange efficiency.

[0058] The compressible expansion space 7 is an airbag with water inlets and outlets. The water inlets and outlets are connected to the water turbine 4 or the feedwater pump via pipes. Specifically, an aramid-polyurethane composite airbag can be used.

[0059] refer to Figure 4 Example 3, based on the above examples: A hydraulically compressed carbon dioxide energy storage system without hot water supply, including a heat exchanger 1, a gas storage tank 2, an electric motor, a generator 3, a water pump, a water turbine 4, a water storage tank 5, and a water storage tank 6; a compressible expansion space 7 is provided in the gas storage tank 2, and carbon dioxide is filled between the gas storage tank 2 and the compressible expansion space 7. The compressible expansion space 7 is connected to the water storage tank 5 via the water pump or the water turbine 4. A heat exchange space is provided on the outside of the gas storage tank 2, and the heat exchange space is connected to the first heat exchange side of the heat exchanger 1. The second heat exchange side of the heat exchanger 1 is connected to the water storage tank 6. The water turbine 4 is connected to the generator; Alternatively, a piston plate can be used to divide the inside of the gas storage tank 2 into upper and lower parts. The lower part serves as the compressible expansion space 7 connected to the water storage tank 5, and the upper part contains carbon dioxide. The heat exchange space is located on the outside of the upper part of the gas storage tank 2, and a sealing ring is provided between the piston plate and the inner wall of the gas storage tank 2.

[0060] In summary, the energy storage and release cycle method of the hydraulically compressed carbon dioxide energy storage system provided by this invention involves the following steps: During energy storage, gaseous carbon dioxide is first adiabatically compressed, then isothermally compressed to saturated liquid carbon dioxide. During energy release, the liquid carbon dioxide first expands adiabatically, then isothermally expands, driving water to impact a turbine and generate electricity. This hydraulically compressed carbon dioxide energy storage system eliminates the need for an additional heating system, directly utilizing water power to compress the carbon dioxide gas, avoiding investment in a cold energy system and reducing overall system investment. The direct hydraulic compression of carbon dioxide eliminates the need for high- and low-pressure side storage tanks in traditional systems, simplifying the system structure, reducing the number of devices, requiring less floor space, having lower geographical requirements, and allowing for flexible installation location selection, greatly improving the system's adaptability and scalability. It also avoids the significant energy consumption and losses during air liquefaction in traditional compressed air energy storage technology, improving the overall system efficiency. Furthermore, it effectively solves the low-temperature problem during low-pressure side carbon dioxide compression, enhancing the system's operational safety and stability.

[0061] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A hydraulically compressed carbon dioxide energy storage system without hot water replenishment, characterized in that, It includes a heat exchanger (1), a gas storage tank (2), an electric motor, a generator (3), a water pump, a water turbine (4), and a water storage tank (5); a compressible expansion space (7) is provided in the gas storage tank (2), carbon dioxide is filled between the gas storage tank (2) and the compressible expansion space (7), the compressible expansion structure (7) is connected to the water storage tank (5) via the water pump or the water turbine (4), a heat exchange space is provided on the outside of the gas storage tank (2), the heat exchange space is connected to the first heat exchange side of the heat exchanger (1), the second heat exchange side of the heat exchanger (1) is connected to the water source, and the water turbine (4) is connected to the generator.

2. The hydraulically compressed carbon dioxide energy storage system without hot water supply according to claim 1, characterized in that, The water pump and turbine (4) are water pump turbines, and the generator (3) and motor are electric generators.

3. The hydraulically compressed carbon dioxide energy storage system without hot water supply according to claim 1, characterized in that, A heat insulation layer is installed on the outside of the heat exchange space of the gas storage tank (2), and a pressure sensor and a temperature sensor are installed in the gas storage tank (2).

4. The hydraulically compressed carbon dioxide energy storage system without hot water supply according to claim 1, characterized in that, A water storage tank (6) is connected to the second heat exchange side of the heat exchanger (1). The water supply pump is a variable frequency pump, and a circulation pump is installed on both pipelines of the heat exchanger (1).

5. The hydraulically compressed carbon dioxide energy storage system without hot water supply according to claim 1, characterized in that, The upper half of the gas storage tank (2) is provided with a shell and is sealed relative to the tank wall of the gas storage tank (2) to form a heat exchange space, and the heat exchange space is provided with reinforced heat exchange fins.

6. A method for charging and discharging energy in a hydraulically compressed carbon dioxide energy storage system without hot water replenishment, characterized in that, During energy storage, gaseous carbon dioxide is first adiabatically compressed, and then isothermally compressed to saturated liquid carbon dioxide. During energy release, the liquid carbon dioxide first expands adiabatically, and then expands isothermally to drive water to impact the turbine and generate electricity.

7. The energy storage and charging cycle method for a hydraulically compressed carbon dioxide energy storage system without hot water replenishment according to claim 6, characterized in that, During the energy storage process, in the initial state, the temperature of gaseous carbon dioxide is 20~25℃ and the pressure is 5.0~5.2MPa. After adiabatic compression, the temperature of carbon dioxide is 30~35℃ and the pressure is 5.5~5.7MPa. It is then isothermally compressed to a liquid state with a temperature of 30~35℃ and a pressure of 6.5~6.7MPa.

8. The energy storage and charging cycle method for a hydraulically compressed carbon dioxide energy storage system without hot water replenishment according to claim 6, characterized in that, During the energy release process, carbon dioxide first expands adiabatically from a temperature of 30~35℃ and a pressure of 6.5~6.7MPa to a temperature of 20~25℃ and a pressure of 5.6~5.8MPa, and then expands isothermally to a temperature of 20~25℃ and a pressure of 5.0~5.2MPa.

9. The energy storage and charging cycle method for a hydraulically compressed carbon dioxide energy storage system without hot water replenishment according to claim 6, characterized in that, During the energy storage process, water is used to exchange heat with carbon dioxide, and the temperature of the water rises from 25°C to 35°C. The water with the increased temperature is then stored in a water tank (6). During the energy release process, the water is used to exchange heat with carbon dioxide, and the temperature drops from 35°C to 25°C. The water is then stored.

10. The energy storage and charging cycle method for a hydraulically compressed carbon dioxide energy storage system without hot water replenishment according to claim 6, characterized in that, The system monitors the temperature and pressure of carbon dioxide, obtains the temperature signal of carbon dioxide and the difference between the temperature and the target temperature, and adjusts the water flow rate for heat exchange with carbon dioxide through PID control. It also obtains the pressure difference between the pressure of carbon dioxide and the target pressure and adjusts the power of the pressurization device through PID control.

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