Multi-stage cold accumulation type air energy storage system and energy conversion method

Abstract

The invention belongs to the technical field of energy storage, and particularly relates to a multi-stage cold accumulation type air energy storage system and an energy conversion method.The multi-stage cold accumulation type air energy storage system comprises a cold accumulator, an energy accumulator, a compressor unit, an expansion unit, a recooler, a recooler, a working medium pipeline, an air inlet pipeline I, an air inlet pipeline II and an air outlet pipeline; the regenerator and the recooler form a circulation loop through a recooling working medium pipeline I; the regenerator and the recooling device form a circulation loop through a recooling working medium pipeline II; the air inlet pipeline communicates with the outside and is connected to the energy storage device through the recooler and the compressor unit in sequence. The air outlet pipeline is led out from the energy storage device and is communicated to the outside through the expansion unit and the recooling device in sequence; the expansion unit is externally connected with a generator set for power generation. According to the air energy storage system, the energy conversion process of a conventional air energy storage system is changed from electric energy-air internal energy and heat energy-electric energy into electric energy and cold energy-air internal energy-electric energy and cold energy, so that high-pressure air or liquid air can become a standardized energy carrier, and longer-period storage, distributed storage and resource calling are achieved.

Description

Technical Field

[0001] This invention belongs to the field of energy storage technology, and in particular to a multi-stage cold storage air energy storage system and energy conversion method. Background Technology

[0002] Against the backdrop of energy structure transformation and the construction of new power systems, the demand for energy storage technology in areas such as grid peak shaving, improving reliability, and enhancing power quality is becoming increasingly urgent. Air energy storage technology, as an important pathway for large-scale, long-term energy storage, mainly includes compressed air energy storage, primarily based on high-pressure gaseous storage, and liquid air energy storage, primarily based on cryogenic liquid storage. Air energy storage can achieve power output at the megawatt level or even gigawatt level, supporting long-term energy storage needs from several hours to several days. Liquid air energy storage, in particular, has a liquid medium with a density approximately 750 times higher than room-temperature air, and can be stored at normal pressure, combining high energy density and high safety. It also eliminates the stringent geographical and hydrological requirements of traditional pumped hydro storage, easily enabling multi-energy complementary power supply, and offering flexible and diverse application scenarios.

[0003] However, current air energy storage technology faces common key bottlenecks in practical application and promotion. During the energy storage phase (charging process), the system generates significant heat of compression while compressing air. Current processes require the simultaneous storage of the air medium (high-pressure gas or liquid air) and high-temperature heat energy to ensure sufficient heat to drive turbine expansion during the energy release phase. This dual dependence of "medium-heat energy" limits its distributed utilization; the storage medium cannot exist independently of the supporting thermal energy storage system, restricting the direct use of air energy storage as a standardized energy carrier on the electricity consumption side. Furthermore, compared to the stable storage of the medium itself, the dissipation of high-temperature heat energy during long-term storage significantly limits the potential of air energy storage for cross-seasonal energy transfer. This necessitates that the air energy storage medium exist in conjunction with specific energy storage power stations, preventing standardized cross-regional transportation, trading, and circulation like bulk energy commodities such as natural gas. To address the above problems, the purpose of this invention is to provide a multi-stage cold storage air energy storage system. By first cooling and then compressing air in a multi-stage series system, and then expanding and then cooling it back, the end stage of energy storage only involves the storage of air and does not require a large-scale thermal storage system, thereby achieving longer-term storage, distributed storage, and resource utilization.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A multi-stage cold storage air energy storage system includes a cold accumulator, an energy storage unit, a compressor unit, an expander unit, a recooler, a return cooler, a recooling working fluid pipeline I, a return cooling working fluid pipeline II, an air inlet pipeline, and an air outlet pipeline. The cold accumulator forms a circulation loop with the recooler through recooling working fluid pipeline I; The cold accumulator forms a circulation loop with the cold return medium through the cold return medium pipeline II; The intake pipe connects to the outside world and passes through the recooler and compressor unit in sequence before connecting to the energy storage unit. The exhaust pipe is led out from the energy storage unit, passes through the expander and the cooler in sequence, and connects to the outside. The compressor unit is powered by an electric motor. The expander unit is connected to an external generator set for power generation.

[0005] As a further preferred option, the energy storage device is a gas storage chamber for storing high-pressure, room-temperature gas.

[0006] As a further preferred option, the energy storage device includes a precooler, a throttle valve, a cryogenic pump, and a storage tank for storing cryogenic liquid gas. The intake pipe connects to the liquid storage tank via the precooler, and the throttle valve is located on the intake pipe between the precooler and the liquid storage tank. The outlet pipeline connects to the expander unit via the precooler, and the cryogenic pump is located on the outlet pipeline between the precooler and the liquid storage tank. The recooling working fluid pipeline I also flows through the precooler to form a circulation loop, and the return working fluid pipeline II also flows through the precooler to form a circulation loop.

[0007] As a further preferred embodiment, the compressor unit includes a multi-stage compressor, the recooler includes multiple recoolers, one recooler corresponds to one stage compressor, one recooler and one stage compressor constitute a recooling unit, and the intake pipeline is connected to multiple recooling units in sequence.

[0008] As a further preferred option, the expander unit includes a multi-stage expander, and the recooler includes multiple recoolers. Each stage expander corresponds to one recooler, and one recooler and the stage expander constitute a recooling unit. The outlet pipeline is sequentially connected to multiple recooling units.

[0009] As a further preferred option, the storage tank is also equipped with a gas discharge pipe for discharging unliquefied gas, which passes through a precooler.

[0010] As a further preferred option, the cold storage unit can be connected to an external refrigeration device or system to provide cooling capacity when the cold storage unit is used for the first time, or to replenish the lost cooling capacity as needed after the system has been used for a long time.

[0011] An energy conversion method for a multi-stage cold storage air energy storage system includes the following steps: Step 1: The refrigerant in the cold accumulator cools down each recooler and precooler through the recooling working fluid pipeline I, and the refrigerant returns to the cold accumulator to continue the circulation. Step 2: Outside air enters the intake pipe and passes through each recooling unit in sequence. First, the ambient air is cooled down, then it enters the compressor for pressurization and heating, and finally forms ambient temperature high-pressure gas. Step 3: The room temperature high-pressure gas is cooled by the precooler and becomes liquid air by the throttling valve. It is then stored in the liquid storage tank. At this time, the electrical energy storage process is completed. The refrigerant in the cold storage is consumed and the precooler is at room temperature. Step 4: Liquid air in the storage tank is pumped into the outlet pipeline by a cryogenic pump, and is heated by the precooler to form cryogenic gas, while the precooler is cooled down. Step 5: The low-temperature gas passes through each cooling unit in sequence, first generating electricity in the expander, then releasing its cooling capacity in the cooler, and finally releasing as ambient temperature and pressure gas. The refrigerant circulation in cooling working fluid pipeline II recovers the cooling capacity of the cooler to the cold storage tank. At this point, the power release process and the cooling capacity recovery process are completed.

[0012] As a further preferred option, the cryogenic gas that has not been liquefied after passing through the throttle valve is discharged through the gas discharge pipe, and the cooling capacity of this portion of the cryogenic gas is transferred to the precooler.

[0013] This invention transforms the energy conversion process of conventional air energy storage systems from electrical energy - liquid air internal energy and thermal energy - electrical energy to electrical energy and cold energy - liquid air internal energy - electrical energy and cold energy, enabling liquid air or high-pressure air to become a standardized energy carrier, thereby achieving longer-term storage, distributed storage, and resource utilization. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the structure of Embodiment 2 of the present invention. Detailed Implementation

[0015] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0016] The present invention provides a multi-stage cold storage air energy storage system, comprising a cold storage unit 3, an energy storage unit, a compressor unit 1, an expander unit 2, a recooler 5, a return cooler 6, a recooling working fluid pipeline I, a return cooling working fluid pipeline II, an air inlet pipeline 12, and an air outlet pipeline 13. The cold accumulator 3 forms a circulation loop with the recooler 5 through the recooling working fluid pipeline I. The cold accumulator 3 is used to store refrigerant, and the recooler 5 is used to pre-cool the air entering the compressor unit 1 by utilizing the cold energy of the refrigerant in the cold accumulator 3. The cold storage 3 forms a circulation loop with the cold storage 6 through the cold working medium return pipeline II. The cold storage 6 is used to recover the cold energy generated by the air energy in the energy storage unit 2 to the refrigerant. The intake pipe 12 connects to the outside, passes through the recooler 5 and the compressor unit 1 in sequence, and is connected to the energy storage unit. The energy storage unit is used to store air energy. The compressor unit 1 is powered by the electric motor unit 7. The compressor unit 1 is used to compress air and generate temperature, and is powered by the electric motor unit 7. The exhaust pipe 13 is led out from the energy storage device and passes through the expander 2 and the cooler 6 in sequence to connect to the outside. The expander 2 is used to perform work, output electrical energy and provide cooling, and is connected to the generator set 8 to generate electricity.

[0017] The compressor unit 1 includes a multi-stage compressor, the recooler 5 includes multiple recoolers 5, one recooler 5 corresponds to one stage compressor, and one recooler 5 and one stage compressor constitute a recooling unit, and the intake pipe 12 is connected to multiple recooling units in sequence.

[0018] Expander unit 2 includes multi-stage expanders, and recooler 6 includes multiple recoolers 6. Each stage expander corresponds to one recooler 6, and one recooler 6 and the stage expander constitute a recooling unit. The outlet pipeline 13 is connected to multiple recooling units in sequence. Example 1

[0019] Reference Figure 1 The energy storage device is a gas storage chamber 41 used to store high-pressure, room-temperature gas. Example 2

[0020] Reference Figure 2 The energy storage device includes a precooler 9, a throttle valve 10, a cryogenic pump 11, and a storage tank 42 for storing cryogenic liquid gas. It can simultaneously achieve cold storage and cold exchange, and the system can operate in any temperature range above -200 degrees Celsius. The intake pipe 12 is connected to the liquid storage tank 42 via the precooler 9, and the throttle valve 10 is located on the intake pipe 12 between the precooler 9 and the liquid storage tank 42. The outlet pipe 13 is connected to the expander unit 2 via the precooler 9, and the cryogenic pump 11 is located on the outlet pipe 13 between the precooler 9 and the liquid storage tank 42. The recooling working fluid pipeline I also flows through the precooler 9 to form a circulation loop, and the return working fluid pipeline II also flows through the precooler 9 to form a circulation loop.

[0021] The storage tank 42 is also equipped with a gas discharge pipe 14 for discharging unliquefied gas. The gas discharge pipe 14 passes through the precooler 9, and the unliquefied low-temperature gas that passes through the throttle valve 10 is discharged through the gas discharge pipe 14. The cooling capacity of this part of the low-temperature gas is transferred to the precooler 9.

[0022] Example 2 illustrates the working principle of a multi-stage cold-storage compressed air energy storage system for storing and releasing electrical energy: Step 1: The refrigerant in the cold storage 3 cools down each of the recoolers 5 and the precooler 9 through the recooling working fluid pipeline I, and the refrigerant returns to the cold storage 3 to continue the circulation. Step 2: Outside air enters the intake pipe 12 and passes through each recooling unit in sequence. First, the ambient air is cooled down, then it enters the compressor for pressurization and heating, and finally forms ambient high-pressure gas. Step 3: The room temperature high pressure gas is cooled by the precooler 9 and becomes liquid air by the throttle valve 10. It is stored in the liquid storage tank 42. At this time, the electrical energy storage process is completed. At this time, the refrigerant in the cold storage accumulator 3 is consumed and the precooler 9 is at room temperature. Specifically, after filtration, outside air first enters the recooler 5 through the intake pipe 12 and is cooled to a cryogenic state. Then, it enters the first-stage compressor inside the compressor unit 1 for compression, after which the air temperature recovers from cryogenic to room temperature. Before entering each stage compressor inlet, the compressed air passes through the recooler 5 to exchange heat with the refrigerant before entering the next stage compressor for compression. The resulting high-pressure, room-temperature air is further cooled to a high-pressure cryogenic state by the precooler 9. The high-pressure cryogenic air then passes through the throttle valve 10, where most of it becomes liquid air and is stored in the liquid storage tank 42. A small portion of the compressed air enters the precooler 9 through the gas discharge pipe 14 to recover cold energy before being discharged into the environment. The refrigerant circulates in the recooling refrigerant pipeline I, transferring the cold energy from the accumulator 3 to the recooler 5 and precooler 9 to complete interstage cooling with the compressed air, and then returns to the accumulator 3 to continue being cooled. The energy storage process ends when the liquid storage tank 42 reaches the required liquid air storage capacity. At this point, all the cold energy in the accumulator 3 is released through the recooler 5 and precooler 9, and the refrigerant in the accumulator 3 is at room temperature. During this process, the electric motor unit 7 supplies power to the compressor unit 1, and the electrical energy and the cold energy in the accumulator 3 are converted into the internal energy of the liquid air and stored.

[0023] Step 4: Liquid air in storage tank 42 is pumped into outlet pipe 13 by cryogenic pump 11, and heated by precooler 9 to form cryogenic gas, while precooler 9 is cooled down. Step 5: The low-temperature gas passes through each cooling unit in sequence, first generating electricity in the expander, then releasing its cooling capacity in the cooler 6, and finally releasing gas at normal temperature and pressure. The refrigerant circulation in the cooling working fluid pipeline II recovers the cooling capacity of the cooler 6 into the cold storage 3. At this point, the power release process and the cooling capacity recovery process are completed.

[0024] Specifically, the liquid air stored in the storage tank 42 is pressurized by the cryogenic pump 11 and enters the precooler 9 to exchange cold energy with the cooling medium. After being heated and vaporized, it enters the first stage expander of the expander unit 2 through the outlet pipe 13 for expansion. After expansion, it becomes cryogenic compressed air and then enters the return cooler 6 through the outlet pipe 13 to cool the cooling medium and restore it to near room temperature. Subsequently, it undergoes multi-stage expansion and inter-stage cooling, and finally is discharged into the atmosphere through the outlet pipe 28 of the final stage return cooler 6.

[0025] The cooling medium circulates in the return cooling medium pipeline II, absorbing the cold energy released by compressed air in the return cooler 6 and absorbing the vaporization cold energy of liquid air in the preheater 9. It is then transported to the cold accumulator 3 for storage as a cooling medium. When the liquid air in the storage tank 42 is consumed to a certain extent, the energy release process ends. The internal energy of the liquid air in the storage tank 42 performs work through the expander, driving the generator set 8 to generate electricity. Part of this electricity is converted into electrical energy and output externally, while the remaining part is converted into cold energy and stored in the cold accumulator 3 for the next energy storage process.

[0026] This invention is easier to integrate with air separation systems and LNG gasification systems for development and utilization, thereby achieving greater economic benefits.

[0027] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A multi-stage regenerative air-based energy storage system, characterized by: It includes a cold accumulator (3), an energy storage unit, a compressor unit (1), an expander unit (2), a recooler (5), a return cooler (6), a recooling working fluid pipeline I, a return cooling working fluid pipeline II, an inlet pipeline (12), and an outlet pipeline (13). The cold storage unit (3) forms a circulation loop with the recooler (5) through the recooling working fluid pipeline I; The cold storage unit (3) forms a circulation loop with the cold storage unit (6) through the cold return working fluid pipeline II; The intake pipe (12) is connected to the outside world and passes through the recooler (5) and compressor unit (1) in sequence to the energy storage unit; The outlet pipe (13) is led out from the energy storage unit and passes through the expander unit (2) and the cooler (6) in sequence to connect to the outside. The compressor unit (1) is powered by the electric motor unit (7); The expander unit (2) is connected to an external generator set (8) for power generation.

2. A multi-stage regenerative air-based thermal energy storage system according to claim 1, wherein: The energy storage device is a gas storage chamber (41) for storing high-pressure, room-temperature gas.

3. A multi-stage regenerative air-based thermal energy storage system according to claim 1, wherein: The energy storage device includes a precooler (9), a throttle valve (10), a cryogenic pump (11), and a storage tank (42) for storing cryogenic liquid gas. The air intake pipe (12) is connected to the liquid storage tank (42) via the precooler (9), and the throttle valve (10) is located on the air intake pipe (12) between the precooler (9) and the liquid storage tank (42); The outlet pipe (13) is connected to the expander unit (2) via the precooler (9), and the cryogenic pump (11) is located on the outlet pipe (13) between the precooler (9) and the liquid storage tank (42); The recooling working fluid pipeline I also flows through the precooler (9) to form a circulation loop, and the return working fluid pipeline II also flows through the precooler (9) to form a circulation loop.

4. A multi-stage regenerative air-based thermal energy storage system according to claim 3, wherein: The compressor unit (1) includes a multi-stage compressor, and the recooler (5) includes multiple recoolers (5). One recooler (5) corresponds to a first-stage compressor, and one recooler (5) and the first-stage compressor constitute a recooling unit. The intake pipe (12) is connected to multiple recooling units in sequence.

5. A multi-stage regenerative air-based thermal energy storage system according to claim 4, wherein: The expander unit (2) includes a multi-stage expander, and the recooler (6) includes multiple recoolers (6). Each first-stage expander corresponds to one recooler (6), and one recooler (6) and the first-stage expander constitute a recooling unit. The outlet pipeline (13) is connected to multiple recooling units in sequence.

6. A multi-stage regenerative air-based thermal energy storage system according to claim 5, wherein: The storage tank (42) is also equipped with a gas discharge pipe (14) for discharging unliquefied gas, and the gas discharge pipe (14) passes through a precooler (9).

7. A multi-stage regenerative air-based thermal energy storage system according to claim 6, wherein: (3) An external refrigeration device or system is connected to the cold storage device to provide cooling capacity when it is first used, or to replenish the lost cooling capacity as needed after the system has been used for a long time.

8. The method of energy conversion of a multi-stage regenerative air-based thermal energy storage system according to claim 7, wherein, Includes the following steps: Step 1: The refrigerant in the cold storage tank (3) cools down each recooler (5) and precooler (9) through the recooling working fluid pipeline I, and the refrigerant returns to the cold storage tank (3) to continue the circulation. Step 2: Outside air enters the intake pipe (12) and passes through each recooling unit in sequence. First, the ambient air is cooled down, then it enters the compressor for pressurization and heating, and finally forms ambient high-pressure gas. Step 3: The room temperature high pressure gas is cooled by the precooler (9), and forms liquid air by the throttle valve (10), which is stored in the liquid storage tank (42). At this time, the electrical energy storage process is completed, and the cold energy of the refrigerant in the cold storage device (3) is consumed. The precooler (9) is at room temperature. Step 4: Liquid air in the storage tank (42) is pumped into the outlet pipeline (13) by the cryogenic pump (11), and is heated by the precooler (9) to form cryogenic gas. The precooler (9) is cooled down. Step 5: The low-temperature gas passes through each cooling unit in sequence, first does work and generates electricity in the expander, then enters the cooling unit (6) to release the cold energy, and finally forms a normal temperature and pressure gas release. The refrigerant circulation of the cooling working fluid pipeline II recovers the cold energy of the cooling unit (6) to the cold storage unit (3). At this time, the power release process and the cold energy recovery process are completed.

9. A method of energy conversion for a multi-stage regenerative air-based thermal energy storage system according to claim 8, wherein: The unliquefied cryogenic gas that passes through the throttle valve (10) is discharged through the gas discharge pipe (14), and the coldness of this portion of cryogenic gas is transferred to the precooler (9).

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