Ultra-high temperature compressed air energy storage system and method

Abstract

The invention discloses an ultrahigh-temperature compressed air energy storage system and method, and relates to the technical field of heat energy engineering. The system comprises a compression energy storage subsystem, an expansion power generation subsystem, a heat regenerator and a fused salt heat storage loop. The compression energy storage subsystem comprises a compressor unit and a heat storage heat exchanger unit, and the expansion power generation subsystem comprises a heat release heat exchanger unit and an expansion unit which alternately operate in time; the heat storage heat exchanger set, the heat regenerator and the compressor set which are used for storing compression heat in the compression process, and the heat release heat exchanger set, the heat regenerator and the expansion set which are used for releasing heat to heat air in the expansion process can be integrated into the same physical equipment set. According to the invention, ultrahigh-temperature compression can be realized, a heat storage temperature area is perfectly matched with binary nitrate solar salt, a low-temperature heat storage system is omitted, the problems of low energy storage efficiency, complex system and high cost of existing compressed air are solved, step-type improvement of efficiency is realized, the system is simplified, and the cost is obviously reduced.

Description

Technical Field

[0001] This invention relates to the field of thermal energy engineering technology, specifically to a compressed air energy storage system and method based on ultra-high temperature compression heat storage and release. Background Technology

[0002] With the continuous and rapid growth of renewable energy installed capacity, compressed air energy storage (CAES), as an important technology choice for large-scale, long-term energy storage, has developed rapidly and has entered the stage of large-scale demonstration and promotion. Its technical routes can be mainly divided into two categories based on the highest temperature reached during the compression process and the heat storage medium used: medium-temperature and high-temperature.

[0003] In the medium-temperature technology route, the outlet temperature of the compression process generally does not exceed 200℃, and medium-pressure water (or a similar liquid medium) is usually used as the heat storage medium to store the heat of compression. This route is relatively simple, but due to the limitation of the heat storage temperature, the system's "electricity-to-electricity" conversion efficiency is generally low, with the efficiency of current demonstration projects being around 65%.

[0004] The high-temperature technology route improves the compression process or equipment to raise the post-compression temperature to a level generally not exceeding 400°C, and uses a combination of heat transfer oil or "ternary molten salt (usually a mixture of potassium nitrate-sodium nitrite-sodium nitrate) + medium-pressure water" to store heat in different temperature zones. Although the efficiency is improved compared to the medium-temperature route, it is still limited by the maximum temperature, and the system's "electricity-to-electricity" conversion efficiency is usually difficult to exceed 70%.

[0005] Both medium- and high-temperature routes have significantly lower system efficiencies than the technologically mature pumped hydro storage (which typically achieves 75%-85%). This lower conversion efficiency has become a major limiting factor hindering the large-scale commercialization of compressed air energy storage technology. The core reason for the low efficiency lies in the insufficient energy grade (i.e., temperature). According to the Carnot cycle principle, higher thermal storage temperatures mean higher initial temperatures can be achieved during the expansion and power generation phase, thus significantly improving power generation efficiency. Furthermore, existing high-temperature routes, in order to cover a wide temperature range from ambient to the highest temperatures, often require multiple thermal storage media and complex multi-system thermal storage structures, increasing system complexity, thermal management difficulty, and initial investment costs.

[0006] Therefore, developing a novel compressed air energy storage system that can overcome existing temperature limitations, achieve higher operating temperatures (e.g., >500℃), thereby obtaining disruptive efficiency improvements, while simplifying the thermal storage system and controlling costs, has become a pressing technical challenge in this field. The "ultra-high temperature" mentioned in this invention refers to a temperature >500℃ reached after air is compressed during the compression process, typically 570-600℃, which significantly exceeds the temperature of existing conventional high-temperature routes. Summary of the Invention

[0007] The present invention aims to overcome the shortcomings of the prior art and provide an ultra-high temperature compressed air energy storage system and method with high system efficiency, large energy storage density, simplified thermal storage system, high integration and significant cost advantages.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] An ultra-high temperature compressed air energy storage system includes a compression energy storage subsystem and an expansion power generation system that operate alternately in time: The compression energy storage subsystem includes: a compressor unit for compressing air to a high temperature and generating high-temperature compression heat, and a heat exchanger unit for storing the high-temperature compression heat in a heat storage medium during the compression process. The expansion power generation system includes: a heat exchanger assembly for extracting heat from the heat storage medium during the expansion process to heat the air, and an expander unit for expanding the heated air to do work. It also includes a regenerator, which is configured to: in compression mode, preheat ambient air entering the system and cool the high-pressure air that has been finally cooled by the heat exchanger assembly; and in expansion mode, preheat ambient high-pressure air from the high-pressure gas storage tank and utilize the waste heat from the exhaust gas after expansion. The heat storage medium is high-temperature molten salt, forming a molten salt heat storage circuit.

[0010] Preferably, the compressor unit is configured to achieve an outlet air temperature of 500°C to 600°C; the heat storage heat exchanger unit is configured to cool the air from the compressor to 290°C to 320°C; and the heat release heat exchanger unit is configured to heat the air entering the expander to 470°C to 570°C.

[0011] Preferably, the compressor unit includes five compressors connected in series; wherein the first four compressors are constant pressure compressors; the fifth compressor is configured to operate under variable pressure, with a constant inlet pressure and an outlet pressure that increases as the pressure in the high-pressure gas storage tank of the system increases.

[0012] More preferably, the outlet pressures of the first four compressor stages are approximately 0.24 to 0.32 MPa, 0.75 to 1.0 MPa, 2.5 to 3.3 MPa, and 7.5 to 10.5 MPa, respectively; the inlet pressure of the fifth compressor stage is constant at a predetermined value within the range of 7.8 to 10.5 MPa, and its outlet pressure varies from this predetermined value to 13 to 18 MPa.

[0013] Preferably, the heat storage medium used in the molten salt heat storage circuit is a binary nitrate solar salt.

[0014] Preferably, the heat storage heat exchanger group and the heat release heat exchanger group are the same set of physical heat exchange equipment groups, and are configured by switching the configuration through pipelines and valves so as to connect to the corresponding air flow paths in compression mode and expansion mode respectively.

[0015] Preferably, the regenerators are physically the same heat exchange equipment, and their function can be switched between compression mode and expansion mode by switching valves.

[0016] Preferably, the multi-stage compressor in the compressor unit and the multi-stage expander in the expander unit are physically the same reversible turbomachinery, and the operation mode is switched by switching the flow channel with valves and adjusting the internal adjustable guide vanes.

[0017] A method for ultra-high temperature compressed air energy storage includes a compression energy storage process and an expansion power generation process; The compression energy storage process includes the following steps: S1. After purification, the ambient air undergoes multi-stage compression to produce high-temperature compressed air with a temperature of 500℃ to 600℃. S2. The high-temperature compressed air is introduced into the heat storage heat exchanger group and cooled to 290°C to 320°C, while the heat of compression is stored in the high-temperature molten salt. S3. The high-pressure air after the final cooling in step S2 is further cooled, and after being compressed by a transformer, it is injected into the high-pressure gas storage tank for storage. The expansion power generation process includes the following steps: P1. Preheat the high-pressure air released from the high-pressure gas storage tank; P2. The preheated high-pressure air is introduced into the heat exchanger group to heat it to 470°C to 570°C using the heat stored in the high-temperature molten salt. P3 causes the heated, high-temperature, and high-pressure air to undergo multi-stage expansion and work.

[0018] Preferably, in the compression energy storage process, the ambient air entering the system is preheated by a regenerator and cooled by the high-pressure air that has been finally cooled by the heat storage heat exchanger group; in the expansion power generation process, the ambient temperature high-pressure air from the high-pressure gas storage tank is preheated by a regenerator and the waste heat of the exhaust gas after expansion is utilized.

[0019] The core technical solution of this invention is to construct an adiabatic compressed air energy storage system that uses ambient air as the working fluid and integrates ultra-high temperature multi-stage compression (including constant pressure and variable pressure stages), high temperature molten salt thermal storage, high pressure air storage, and high temperature multi-stage expansion reheat power generation. Compared with the prior art, this invention has the following significant advantages: 1. System efficiency achieves a leapfrog improvement: By realizing ultra-high temperature compression and reheat expansion, a high-quality thermodynamic cycle is constructed, enabling the system's "electricity-to-electricity" conversion efficiency to exceed 75%, which is significantly better than existing medium-temperature and high-temperature compressed air energy storage technologies; 2. High energy density, reduced equipment and gas storage capacity: Ultra-high temperatures significantly increase the energy density per unit mass of air. With the same energy storage capacity, the specifications of core equipment such as compressors, expanders, and heat exchangers, as well as the volume of high-pressure gas storage facilities, can be effectively reduced, lowering initial investment costs. 3. Fundamental Simplification of Thermal Storage Medium and System: Unlike existing technologies that require thermal storage covering the entire temperature range from ambient to maximum, this invention optimizes and enhances the heat quality within the system through a regenerator, perfectly concentrating the core thermal storage and release processes within a single high-temperature range of 290℃ to 600℃. This temperature range highly overlaps with the recommended operating temperature range (approximately 290℃-565℃) of commercially available, low-cost binary nitrate "solar salt." The disruptive advantage of this design is that it completely eliminates the need for dedicated storage of heat below 290℃, thus avoiding the need for multiple thermal storage media and complex multiple thermal storage systems, as required by existing technologies, such as heat transfer oil, low-temperature molten salt, or water. This fundamentally simplifies the thermal storage system and significantly reduces its cost. 4. High system integration and high equipment utilization: By sharing molten salt thermal storage / heat release equipment, sharing regenerators, and the optional reversible turbine unit design, the system achieves multi-functional reuse of equipment, minimizes the number of independent equipment, simplifies pipeline layout and control system, and improves space utilization and economy. 5. Optimized operating strategy and strong adaptability: The fifth-stage compressor adopts a variable pressure operation design, which can adapt to the characteristic of the gas storage tank continuously increasing pressure during the filling process, so that the compressor always operates in the high-efficiency operating range, improving the overall energy efficiency of the entire energy storage process.

[0020] This system is particularly suitable for large-scale (hundred megawatts) and long-term (several hours to tens of hours) energy storage on the grid side. It can efficiently realize the mutual conversion of electrical energy with high-temperature and high-pressure air pressure potential energy and molten salt thermal energy, aiming to significantly improve the system's cycle efficiency and energy storage density. Attached Figure Description

[0021] Figure 1 This is a system principle flowchart of Embodiment 1 of the present invention (five-level compression, four-level expansion basic architecture).

[0022] Figure 2 This is a system principle flowchart of Embodiment 2 of the present invention (the heat exchanger and the regenerator are shared).

[0023] Figure 3This is a system principle flowchart of Embodiment 3 of the present invention (shared by heat exchanger, regenerator and pressure expansion unit). Detailed Implementation

[0024] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings, specific embodiments, and comparative examples. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Example 1

[0025] like Figure 1 As shown, this embodiment provides an ultra-high temperature compressed air energy storage system, which mainly includes a compression energy storage subsystem and an expansion power generation system, which operate alternately in time.

[0026] The compressed energy storage subsystem includes: an air filter 1, a first regenerator 2, a first-stage compressor C1 (equipped with a first electric motor M1), a second-stage compressor C2 (equipped with a second electric motor M2), a third-stage compressor C3 (equipped with a third electric motor M3), a fourth-stage compressor C4 (equipped with a fourth electric motor M4), and a fifth-stage compressor C5 (equipped with a fifth electric motor M5), respectively installed at the outlets of the first-stage compressor C1, the second-stage compressor C2, the third-stage compressor C3, and the fourth-stage compressor C4, a first molten salt heat exchanger HX1, a second molten salt heat exchanger HX2, a third molten salt heat exchanger HX3, and a fourth molten salt heat exchanger HX4, a cooler 3, and a high-pressure gas storage tank 4. The cold-side outlet of the first regenerator 2 is connected to the inlet of the first compressor C1. The outlets of the first four compressors are connected to the hot-side inlets of their respective molten salt heat exchangers. The hot-side outlets of the first three molten salt heat exchangers are connected to the inlets of the next compressor. The hot-side outlet of the fourth molten salt heat exchanger HX4 is connected to the hot-side inlet of the first regenerator 2. The hot-side outlet of the first regenerator 2 is connected to the inlet of the fifth compressor C5. The outlet of the fifth compressor C5 is connected to the high-pressure gas storage tank 4 via the cooler 3. The motor is the working drive motor for the compressor.

[0027] The expansion generator system includes: a high-pressure gas storage tank 4, a second regenerator 5, a first molten salt exothermic heat exchanger TX1, a second molten salt exothermic heat exchanger TX2, a third molten salt exothermic heat exchanger TX3, a fourth molten salt exothermic heat exchanger TX4, a first-stage expander E1, a second-stage expander E2, a third-stage expander E3, and a fourth-stage expander E4 connected in series, a generator 6, and an exhaust silencer 7. The cold-side outlet of the second regenerator 5 is connected to the cold-side inlet of the first molten salt exothermic heat exchanger TX1. The cold-side outlets of each molten salt exothermic heat exchanger are connected to the corresponding expander inlets. The outlets of the first three expanders are connected to the cold-side inlets of the next molten salt exothermic heat exchanger, and the outlet of the fourth expander E4 is connected to the hot-side inlet of the second regenerator 5.

[0028] In this embodiment, the four-stage molten salt heat storage heat exchanger and the four-stage molten salt heat release heat exchanger are physically independent devices, but they are all connected to the same molten salt heat storage circuit that includes a hot storage tank and a cold storage tank. The first regenerator 2 and the second regenerator 5 are also independent devices.

[0029] The system operates according to the following process:

[0030] In the ultra-high temperature operating range, the compressor unit is generally configured to achieve an outlet air temperature of 500°C to 600°C (preferably 570°C to 600°C); the heat storage heat exchanger unit is configured to cool the air from the compressor to 290°C to 320°C; the heat release heat exchanger unit is configured to heat the air entering the expander to 470°C to 570°C (preferably 550°C to 570°C); the outlet pressures of the first four compressor stages are 0.24~0.32 MPa, 0.75~1.0 MPa, 2.5~3.3 MPa, and 7.8~10.5 MPa, respectively; the inlet pressure of the fifth compressor stage is a predetermined value within the range of 7.8~10.5 MPa, and its outlet pressure varies from this predetermined value to 13~18 MPa.

[0031] The parameters listed in this example are exemplary data under a specific design condition, used to demonstrate the working principle and potential of the present invention. Those skilled in the art will understand that the actual operating parameters can be adjusted within the above core process framework according to different molten salt target temperatures, environmental conditions and equipment selections.

[0032] (a) Compression energy storage process: Air pretreatment and primary preheating: Ambient air is first purified by air filter 1, and then enters the cold side channel of the first regenerator 2 for preheating.

[0033] The first four stages of constant pressure compression-heat storage cycle: First stage compression and heat storage: After preheating, the air enters the first stage compressor C1, where it is compressed to approximately 0.32 MPa and its temperature rises to approximately 580°C. It then enters the first molten salt heat exchanger HX1, where it transfers heat to the molten salt in the molten salt circuit. The air is cooled to approximately 315°C, while the molten salt is heated from approximately 300°C.

[0034] Second stage compression and heat storage: The cooled air enters the second stage compressor C2, is compressed to about 1.0 MPa, and the temperature rises again to about 580°C. Then it enters the second molten salt heat storage heat exchanger HX2 to be cooled to about 315°C and the molten salt is heated again.

[0035] Third stage compression and heat storage: Air enters the third stage compressor C3 and is compressed to approximately 3.3 MPa, with an outlet temperature of approximately 580°C. It then enters the third stage molten salt heat exchanger HX3 and is cooled to approximately 315°C.

[0036] Fourth stage compression and heat storage: Air enters the fourth stage compressor C4 and is compressed to approximately 10.5 MPa, with an outlet temperature of approximately 580°C. It then enters the fourth stage molten salt heat storage heat exchanger HX4 and is cooled to approximately 315°C.

[0037] In this process, the molten salt is heated in parallel to reach the target temperature (e.g., 565°C) and stored in a hot molten salt storage tank.

[0038] Intermediate cooling and fifth-stage variable compression: After this, air enters the hot side of the first regenerator 2, transferring the remaining heat to the cold side intake air, and its own temperature drops to close to the ambient temperature.

[0039] The cooled high-pressure air (approximately 10.5 MPa) enters the fifth-stage compressor C5 for variable-pressure compression. This fifth-stage compressor C5 operates in variable-pressure mode, with a constant inlet pressure of approximately 10.5 MPa. However, its outlet pressure is not fixed; instead, it gradually increases from an initial pressure (e.g., 10.5 MPa) to a final pressure (e.g., 18 MPa) as the pressure inside the high-pressure gas storage tank 4 rises. This design aims to accommodate the continuously increasing pressure within the gas storage tank during filling, thereby improving overall operating efficiency.

[0040] Final gas storage: The high-pressure air (10.5-18 MPa) from the outlet of the fifth stage compressor C5 is further cooled to room temperature by the cooler 3 and then injected into the high-pressure gas storage tank 4 for storage.

[0041] (II) Expansion power generation process: High-pressure air release and preheating: When power generation is required, the ambient temperature high-pressure air in the high-pressure gas storage 4 is released and first enters the cold side of the second regenerator 5 for preheating.

[0042] Four-stage heat absorption-expansion power generation cycle: The first stage of heat absorption and expansion: The preheated high-pressure air enters the first molten salt heat exchanger TX1, where it is heated to approximately 550°C by the high-temperature molten salt from the molten salt loop heat tank. It then enters the first stage expander E1 to expand and perform work.

[0043] The second stage of heat absorption and expansion: the air discharged from E1 enters the second molten salt heat exchanger TX2, is heated again to about 550°C, and then enters the second stage expander E2 to expand and do work.

[0044] The third stage of heat absorption and expansion: Air enters the third-stage molten salt heat exchanger TX3 and absorbs heat to approximately 550°C. It then enters the third-stage expander E3 to expand and perform work.

[0045] The fourth stage of heat absorption and expansion: Air enters the fourth molten salt heat exchanger TX4 and absorbs heat to approximately 550°C. It then enters the fourth stage expander E4 to expand and perform work.

[0046] Waste heat recovery and exhaust: The low-pressure, low-temperature air discharged from the fourth-stage expander E4 enters the hot side of the second regenerator 5 to preheat the high-pressure intake air and recover waste heat. The final exhaust temperature (usually still above 150°C) can be used for district heating or industrial steam, or directly vented.

[0047] It should be noted that, due to the addition of the regenerator, the average operating temperature of the compressor unit is further increased. Traditional compressor designs are unable to cope with the thermal shock caused by frequent starts, which increases the risk of thermal expansion mismatch between the rotor and the casing, and easily leads to dynamic and static friction and thermal stress fatigue of the unit. Solution: (1) Staged independent hot turning: Add an electric hot turning device at the connection of the compressor unit; during the non-energy storage period of the system, use the residual heat of the molten salt system to maintain the compressor casing at a normal temperature preheating state above 300℃ through the molten salt heat exchanger to reduce the temperature difference stress during start-up. (2) Regenerated air intake regulation: A bypass regulating valve can be added to the cold side inlet of the first regenerator 2. In the initial stage of start-up, the air does not pass through the regenerator for preheating and directly enters the first stage compressor C1 to reduce the overall heat load; after the rotors of each stage are heated evenly, the regulating valve is gradually switched to increase the flow rate on the regenerator side and achieve a stable increase in the compressor inlet temperature.

[0048] One of the core functions of a regenerator is to manage the heat grade within the system. It essentially recovers and utilizes low-grade heat below 290°C directly within the system without the need for an external heat storage system. This concentrates the heat that would otherwise be stored in molten salt into a high-grade range above 290°C, creating the necessary conditions for subsequently using a single, inexpensive solar salt as the heat storage medium.

[0049] The preferred heat storage medium used in the system is binary nitrate solar salt, whose operating temperature range (approximately 290℃ ~ 565℃) closely matches the core heat storage / release temperature range of this system (approximately 290℃ ~ 600℃). It is understood that other heat storage media capable of stable operation within the 290℃ to 600℃ temperature range and possessing good heat transfer performance, such as nitrates and chloride molten salts with different proportions, should also fall within the scope of protection of this invention. Example 2: Heat exchanger and regenerator shared

[0050] like Figure 2 As shown, based on Embodiment 1, this embodiment further achieves a high degree of device integration.

[0051] Molten salt heat exchange equipment is shared: The first to fourth stages of molten salt thermal storage heat exchangers and the first to fourth stages of molten salt exothermic heat exchangers are physically identical heat exchange equipment, with functional switching achieved through valve group switching; the other two heat exchange systems share the same molten salt thermal storage circuit, which includes a hot storage tank and a cold storage tank. During the compression process, opening the compressor inlet and outlet valves and closing the expander inlet and outlet valves connects the first to fourth stages of molten salt heat exchangers to the first to fourth stages of compressors, transferring heat from the air to the molten salt. During the expansion process, closing the compressor inlet and outlet valves and opening the expander inlet and outlet valves connects the first to fourth stages of molten salt heat exchangers to the first to fourth stages of expanders, transferring heat from the molten salt to the air. The valve group can use three-way valves or four-way valves for branch switching; the flow paths and directions of molten salt and air are switched by program-controlled combinations of valve opening and closing.

[0052] In actual engineering, the flow rate, pressure and working time of the compression process (cold side is ambient air intake) and the expansion process (hot side is expander exhaust) are completely different. Frequent switching will cause alternating stress inside the heat exchanger, and the molten salt or high-pressure air remaining in the flow channel will cause system disturbance. Solution: (1) Integrated switching valve group, using a valve group switching logic linked by PLC. When switching between compression mode and expansion mode, the valve group can be automatically switched. (2) Optimized counterflow arrangement structure: By adopting a reversible flow channel design for the heat exchanger, it is ensured that no matter whether in the compression preheating or expansion reheating stage, the fluid direction is reversed, but the fluid maintains complete counterflow contact, maximizing heat exchange efficiency. (3) Thermal stress self-compensation connection: A pressure balance compensator is used at the connection between the heat exchanger and the pipeline to overcome the several centimeter-level pipeline expansion and contraction displacement caused by high temperature fluctuations, and to prevent ultra-high temperature air leakage at the flange connection due to thermal expansion difference.

[0053] Shared Regenerator: The first regenerator 2 and the second regenerator 5 are physically the same heat exchanger. To achieve safe and rapid process switching between compression and expansion modes, a set of isolation and bypass valve groups (such as...) is connected to the four ports of the integrated regenerator. Figure 3 As shown, a bypass line is added to the air-side outlet pipe of the integrated regenerator. During the initial mode switching phase, a portion of the airflow is introduced into the bypass line. Once the internal temperature field of the integrated regenerator stabilizes through self-regulation, the main flow is gradually switched in. This design effectively reduces thermal stress fatigue in the heat exchanger, improving equipment reliability and service life.

[0054] Shared motor: The drive motors of the first four compressor stages are physically integrated into a single shared motor, which drives all four compressor stages simultaneously through a transmission mechanism (such as a gearbox or coupling assembly).

[0055] This embodiment design greatly saves on equipment investment and floor space, and simplifies the system. Example 3: Shared expansion unit

[0056] like Figure 3 As shown, this embodiment achieves a deeper level of integration compared to embodiment two.

[0057] Shared Turbomachinery: The first four stages of compressors and the four stages of expanders are physically integrated into a single reversible turbomachinery unit (or "compression-expansion integrated unit"). This integrated unit is equipped with guide vanes with adjustable stroke under all operating conditions at the inlet of each stage impeller. The guide vanes are controlled by a PLC control system to rotate at different angles when switching between compression and expansion modes, thereby precisely changing the geometric expansion / contraction characteristics of the flow channel.

[0058] Specifically, in energy storage mode, air flows in from the low-pressure end of the unit, and the adjustable guide vanes form a contraction channel. The unit operates as a four-stage centrifugal compressor sequence, progressively pressurizing and heating the air to approximately 600°C. In energy release mode, air flows in from the high-pressure end in the opposite direction, and the adjustable guide vanes synchronously rotate to form an expansion channel. The unit operates as an expander sequence, performing depressurization work.

[0059] To cope with the reverse thermal shock and thrust changes caused by the sharp reversal of airflow direction and pressure under ultra-high temperature conditions, the main shaft of this integrated unit adopts a thrust bearing with bidirectional thrust bearing capacity to ensure that the mechanical structure remains stable during mode switching and all operating conditions.

[0060] System valve switching: To achieve the system-wide process switching required for the reverse operation of the turbomachinery, the system controls the entire airflow path to switch between compression and expansion processes through an integrated valve assembly. Furthermore, to further enhance integration, the electric motor driving the compressor and the generator driven by the expander can also be physically integrated into a single reversible motor / generator.

[0061] This solution represents the highest level of system integration, requiring the fewest devices and achieving the highest degree of integration.

[0062] Based on the above system, the ultra-high temperature compressed air energy storage method of the present invention includes the sequence of steps described in the above compression energy storage process and expansion power generation process. Its core is to use the same set of physical heat exchange equipment and the same molten salt circuit to alternately realize the storage and release of high temperature compression heat.

[0063] Project Implementation and Material Selection: Materials for high-temperature components: The flow channels of the compressor and expander and the tube bundles of the heat exchanger must be made of high-temperature resistant alloys.

[0064] Heat exchanger selection: Molten salt heat exchangers / absorbing heat exchangers can be printed circuit board heat exchangers (PCHE) or high-performance shell and tube heat exchangers to balance pressure resistance, temperature resistance and compactness.

[0065] Control Strategy: The system needs to be equipped with an advanced control system to accurately coordinate the operation of equipment at all levels, valve switching (especially for shared equipment), and the variable pressure operation curve of the fifth stage compressor, so as to ensure smooth mode switching and efficient system operation.

[0066] Based on the above system, the corresponding ultra-high temperature compressed air energy storage method of the present invention includes a compression energy storage process and an expansion power generation process, the specific steps of which are as follows: (a) The compression energy storage process shall be performed in sequence as follows:

[0067] S1. Air Compression Heat Generation: After purification, ambient air undergoes multi-stage compression to generate high-temperature compressed air with a temperature of 500°C to 600°C. Preferably, this preheating is achieved through a regenerator; this step includes the first four stages of constant-pressure compression.

[0068] S2, Compression Heat Storage: The high-temperature compressed air generated in step S1 is introduced into the heat storage heat exchanger group and cooled to 290°C to 320°C, while the compression heat is stored in high-temperature molten salt.

[0069] S3. Final Processing and Storage: The high-pressure air, after final cooling in step S2, is further cooled and / or subjected to variable-pressure compression before being injected into a high-pressure gas storage tank. Preferably, this step includes cooling the air via a regenerator, then subjecting it to variable-pressure compression by a fifth-stage compressor, followed by further cooling via a cooler before being injected into the gas storage tank.

[0070] (II) The expansion power generation process shall be carried out in sequence as follows:

[0071] P1. High-pressure air release and preheating: The high-pressure air released from the high-pressure gas storage tank is preheated. Preferably, this preheating is achieved through a regenerator.

[0072] P2. Air heating: Preheated high-pressure air is introduced into the heat exchanger group and heated to 470°C to 570°C using the heat stored in the high-temperature molten salt.

[0073] P3. Expansion and Work: The heated, high-temperature, and high-pressure air undergoes multi-stage expansion and work. Preferably, this step is multi-stage expansion, and the air is reheated by the heat exchanger assembly before each stage of expansion.

[0074] P4. Waste Heat Recovery: The exhaust gas after expansion and work is either recovered and reused or vented. Preferably, the exhaust gas is introduced into a regenerator to recover waste heat.

[0075] The technical features of this invention not described can be implemented by or using existing technology, and will not be repeated here. Of course, the above description is not a limitation of this invention, and this invention is not limited to the examples above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of this invention should also fall within the protection scope of this invention.

Claims

1. An ultra-high temperature compressed air energy storage system, comprising a compression energy storage subsystem and an expansion power generation system that operate alternately in time, characterized in that: The compression energy storage subsystem includes: a compressor unit for compressing air to a high temperature and generating high-temperature compression heat, and a heat exchanger unit for storing the high-temperature compression heat in a heat storage medium during the compression process. The expansion power generation system includes: a heat exchanger assembly for extracting heat from the heat storage medium during the expansion process to heat the air, and an expander unit for expanding the heated air to do work. It also includes a regenerator, which is configured to: in compression mode, preheat ambient air entering the system and cool the high-pressure air that has been finally cooled by the heat exchanger assembly; and in expansion mode, preheat ambient high-pressure air from the high-pressure gas storage tank and utilize the waste heat from the exhaust gas after expansion. The heat storage medium is high-temperature molten salt, forming a molten salt heat storage circuit.

2. The ultra-high temperature compressed air energy storage system according to claim 1, characterized in that, The compressor unit is configured to achieve an outlet air temperature of 500°C to 600°C; the heat storage heat exchanger unit is configured to cool the air from the compressor to 290°C to 320°C; and the heat release heat exchanger unit is configured to heat the air entering the expander to 470°C to 570°C.

3. The ultra-high temperature compressed air energy storage system according to claim 2, characterized in that, The compressor unit includes five compressors connected in series; the first four compressors are constant pressure compressors; the fifth compressor is configured to operate under variable pressure, with a constant inlet pressure and an outlet pressure that increases as the pressure in the high-pressure gas storage tank of the system increases.

4. The ultra-high temperature compressed air energy storage system according to claim 3, characterized in that, The outlet pressures of the first four compressor stages are 0.24 to 0.32 MPa, 0.75 to 1.0 MPa, 2.5 to 3.3 MPa, and 7.5 to 10.5 MPa, respectively; the inlet pressure of the fifth compressor stage is constant at a predetermined value within the range of 7.8 to 10.5 MPa, and its outlet pressure varies from this predetermined value to 13 to 18 MPa.

5. The ultra-high temperature compressed air energy storage system according to claim 1, characterized in that, The heat storage medium used in the molten salt heat storage circuit is a binary nitrate solar salt.

6. The ultra-high temperature compressed air energy storage system according to claim 1, characterized in that, The heat storage heat exchanger group and the heat release heat exchanger group are the same set of physical heat exchange equipment groups, and are configured by switching pipelines and valves to connect to the corresponding air flow paths in compression mode and expansion mode respectively.

7. The ultra-high temperature compressed air energy storage system according to claim 1, characterized in that, The regenerators are physically the same heat exchange equipment, and their function can be switched between compression mode and expansion mode by switching valves.

8. The ultra-high temperature compressed air energy storage system according to claim 1, characterized in that, The multi-stage compressor in the compressor unit and the multi-stage expander in the expander unit are physically the same reversible turbomachinery. The operation mode is switched by switching the flow channel with valves and adjusting the internal adjustable guide vanes.

9. A method for storing energy in ultra-high temperature compressed air, characterized in that, The ultra-high temperature compressed air energy storage system as described in any one of claims 1-8 includes a compression energy storage process and an expansion power generation process; The compression energy storage process includes the following steps: S1. After purification, the ambient air undergoes multi-stage compression to produce high-temperature compressed air with a temperature of 500℃ to 600℃. S2. The high-temperature compressed air is introduced into the heat storage heat exchanger group and cooled to 290°C to 320°C, while the heat of compression is stored in the high-temperature molten salt. S3. The high-pressure air after the final cooling in step S2 is further cooled, and after being compressed by a transformer, it is injected into the high-pressure gas storage tank for storage. The expansion power generation process includes the following steps: P1. Preheat the high-pressure air released from the high-pressure gas storage tank; P2. The preheated high-pressure air is introduced into the heat exchanger group to heat it to 470°C to 570°C using the heat stored in the high-temperature molten salt. P3 causes the heated, high-temperature, and high-pressure air to undergo multi-stage expansion and work.

10. The ultra-high temperature compressed air energy storage method according to claim 9, characterized in that, In the compression energy storage process, the ambient air entering the system is preheated by a regenerator and cooled by the high-pressure air that has been finally cooled by the heat exchanger group. In the expansion power generation process, the ambient temperature high-pressure air from the high-pressure gas storage tank is preheated by a regenerator and the waste heat from the exhaust gas after expansion is utilized.

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