A large-capacity compressed air energy storage system and a method for operating the same

Abstract

This invention discloses a large-capacity compressed air energy storage system and its operation method, belonging to the field of energy storage technology. The system includes a high-pressure hot water storage tank, whose interior, from top to bottom, consists of a high-temperature zone, a thermal stratification transition zone, and a low-temperature zone. A horizontal baffle plate suppresses the disturbance of water stratification caused by longitudinal water flow, thus maintaining thermal stratification. Upper and lower water distributors control the uniform horizontal distribution of high-temperature and low-temperature water entering and exiting the storage tank. A temperature sensor array is uniformly arranged from bottom to top on the internal sidewall of the high-pressure hot water storage tank. This invention, by adopting a single-tank stratified thermal storage architecture instead of the traditional complex configuration, significantly reduces the number of system pipelines and valves, completely eliminates auxiliary power consumption, and occupies only 50% to 60% of the floor space of a dual-tank solution. The stratified structure of the high-pressure hot water storage tank, combined with the baffle plate and temperature monitoring, ensures that the temperature quality of the usable hot water inside the tank remains stable during charge-discharge cycles, significantly improving the operating efficiency of the energy storage system.

Description

Technical Field

[0001] This invention belongs to the field of energy storage technology, and in particular relates to a large-capacity compressed air energy storage system and its operation method. Background Technology

[0002] Compressed air energy storage features large capacity, high safety, long service life, and low construction cost. It can effectively solve the problem of grid connection difficulties for new energy power generation such as solar and wind power, becoming an important support for the construction of new power systems. Based on the method of handling the heat of compression, it is divided into afterburning compressed air energy storage and non-afterburning compressed air energy storage.

[0003] In the field of non-combustion compressed air energy storage, the mainstream approach uses either heat transfer oil or molten salt (Scheme 1) or high-pressure hot water (Scheme 2) for heat storage. Scheme 1 uses heat transfer oil or molten salt as the heat storage medium, heating the air to 400-600℃ during compression, storing the heat of compression, and then reheating the air during expansion to achieve the highest possible electro-electric conversion efficiency. However, Scheme 1 faces engineering bottlenecks due to its high-temperature insulation design. The operating temperature of 400-600℃ places extremely high demands on the materials of the compressor and expander. Heat transfer oil poses leakage and fire hazards at high temperatures, while molten salt exhibits significant corrosion problems in pipelines and heat exchangers at high temperatures. This significantly increases the system cost of high-temperature insulation CAES, and equipment lifespan and maintenance costs become limiting factors for large-scale deployment. Based on a 300MW scale estimate, the cost of a heat storage system using the heat transfer oil scheme accounts for approximately 25%-30% of the total investment.

[0004] Therefore, Option 2 has become the technological direction pursued by the industry. Regarding Option 2, patent CN 114320840 A proposes a compressed air energy storage system and its operation method that utilizes high-pressure, high-temperature hot water for heat storage. Patent CN 114320840 A employs two independent tanks: a cold water tank and a hot water tank, connected by an upper gas connection pipe, and relies on an external air supply mechanism (air compressor) to maintain a pressure of no less than 1 MPa within the tanks. This dual-tank + connecting pipe + external gas supply architecture leads to the following problems: First, the gas connecting pipe is prone to condensation and corrosion in high-temperature and high-humidity environments, resulting in decreased long-term operational reliability. Second, the external gas supply mechanism needs to operate continuously to compensate for system leaks and pressure fluctuations, increasing auxiliary power consumption (approximately 1% to 2% of the power plant's self-consumption). Third, the dual-tank arrangement increases the footprint and pipeline complexity. In a 300MW-level large-capacity scenario, the total volume requirement for cold and hot water storage tanks reaches several thousand cubic meters, significantly increasing the difficulty of ground layout for the dual-tank solution. Fourth, patent CN 114320840 A does not address the internal thermal stratification structure design of the thermal storage tank, which may lead to mixing of cold and hot water within the tank, reducing the usable thermal storage capacity. Fifth, the thermal storage process in patent CN 114320840 A is based on a "dual-tank water migration" mode. During charging and discharging, the water used as the thermal storage medium needs to be repeatedly pumped between the two tanks, resulting in high water transport power consumption and a large number of connecting pipes and valves between the tanks, significantly impacting system reliability due to pipeline leakage risks.

[0005] Therefore, the industry currently lacks a technical route for "medium-temperature insulation" (compression final temperature of about 180~200℃): instead of using high-temperature heat transfer oil / molten salt, it adopts relatively mild 180℃ high-pressure hot water as the heat storage medium, and at the same time completes the whole system integration design from compressor unit to heat storage system to expander unit to gas storage for the large-capacity gas storage scenario of underground gas storage.

[0006] Therefore, it is urgent to propose a medium-temperature adiabatic compressed air energy storage system architecture with high-pressure hot water as the heat storage medium, and its full-process operation method of charging-heat storage-discharge, for large-capacity (300MW and above) underground gas storage scenarios. Summary of the Invention

[0007] In view of the above-mentioned problems, the present invention discloses a large-capacity compressed air energy storage system and its operation method.

[0008] The present invention adopts the following technical solution: A large-capacity compressed air energy storage system includes a high-pressure hot water storage tank. The high-pressure hot water storage tank adopts a single-tank layered heat storage architecture. From top to bottom, the interior of the high-pressure hot water storage tank consists of a high-temperature zone, a thermal stratification transition zone, and a low-temperature zone. The thermal stratification transition zone is equipped with a horizontal baffle plate to suppress disturbances to the water stratification caused by longitudinal water flow, thus maintaining thermal stratification. The high-temperature zone is equipped with an upper water distributor, and the low-temperature zone is equipped with a lower water distributor. The upper water distributor ensures that the high-temperature water entering and exiting the high-temperature zone is evenly distributed horizontally, and the lower water distributor ensures that the low-temperature water entering and exiting the low-temperature zone is evenly distributed horizontally. An array of temperature sensors is evenly arranged from bottom to top on the internal sidewall of the high-pressure hot water storage tank. The high-pressure hot water storage tank is used to provide low-temperature water to the heat exchanger of the energy storage system or high-temperature water to the reheater.

[0009] Furthermore, the opening ratio of the horizontal guide plate is 25%~35%; the upper water distributor is composed of an upper annular porous tube, and the lower water distributor is composed of a lower annular porous tube. The two ends of the upper annular porous tube are respectively connected to the high-temperature water outlet and the high-temperature water inlet; the two ends of the lower annular porous tube are respectively connected to the low-temperature water outlet and the low-temperature water inlet; the energy storage system includes two or more high-pressure hot water storage tanks connected in parallel.

[0010] Furthermore, the system also includes: A multi-stage compressor unit, wherein the multi-stage compressor unit consists of N compressors connected in series, where N≥3, and an intercooler is provided between each stage of compressors. The outlet of the final stage compressor is connected to the inlet of the underground gas storage tank through a compressed air main pipeline. The gas storage facility uses at least one underground space selected from salt caverns, hard rock chambers, or aquifers as the storage location for compressed air. A multi-stage expander unit, wherein the multi-stage expander unit consists of K stages of expanders connected in series, where K≥2, and a reheater is installed between each stage of expander. The inlet of the first stage expander is connected to the outlet of the underground gas storage tank via a pressure regulating valve group. The high-temperature water inlet is connected to the hot water side of the intercooler via a high-pressure hot water circulation pipeline, and the high-temperature water outlet is connected to the hot water side of the reheater via a high-pressure hot water circulation pipeline.

[0011] Furthermore, the energy storage system also includes a final-stage compression heat utilization subsystem, which includes a waste heat diversion heat exchanger installed at the outlet of the final-stage compressor. The waste heat diversion heat exchanger distributes the compression heat at the outlet of the final-stage compressor according to temperature grade to the external heating circuit, the inlet preheating circuit, and the high-pressure hot water storage circuit.

[0012] Furthermore, the high-temperature zone has a temperature of 150~190℃, and the low-temperature zone has a temperature of 40~60℃; the temperature sensor array has no fewer than 8 measuring points; and a level gauge is installed on one side of the tank to monitor the water level inside the tank.

[0013] Furthermore, when multiple high-pressure hot water storage tanks are operated in parallel, each tank is controlled to switch on and off via an independent valve, and the charging and discharging rates of each tank are independently adjusted; the gas storage tank and the expander unit are connected via a pressure regulating valve group, which is used to adjust the pressure changes in the gas storage tank and the stability of the inlet pressure of the expander unit.

[0014] Furthermore, the waste heat diversion heat exchanger includes a three-stage heat exchanger group connected in series, namely a first-stage heat exchanger, a second-stage heat exchanger, and a third-stage heat exchanger, wherein: The hot-side inlet of the first-stage heat exchanger is connected to the outlet of the final-stage compressor, the hot-side outlet of the first-stage heat exchanger is connected to the hot-side inlet of the second-stage heat exchanger, and the cold side of the first-stage heat exchanger is connected to the external heating circuit. The hot-side outlet of the second-stage heat exchanger is connected to the hot-side inlet of the third-stage heat exchanger. The cold side of the second-stage heat exchanger is connected to the inlet preheating circuit. An inlet preheater is installed at the beginning of the inlet preheating circuit and is arranged on the inlet duct of the first-stage compressor. The hot-side outlet of the third-stage heat exchanger is connected to the inlet of the gas storage tank via a pipeline, and the cold-side outlet of the third-stage heat exchanger is connected to the high-temperature water inlet of the high-pressure hot water storage tank.

[0015] An operation method for the above-mentioned energy storage system, the operation method including a charging mode, a discharging mode and a combined operation mode; The charging modes include: In charging mode, the high-temperature compressed air from the outlet of the final stage compressor enters the waste heat diversion heat exchanger and is distributed in three stages according to temperature grade: the highest temperature part is released to external heat users through the heating heat exchanger; the second highest temperature part is preheated to the ambient air entering the first stage compressor through the inlet preheater in the inlet preheating circuit; the remaining heat is combined with the hot water side outlet of each stage intermediate cooler and flows into the high-temperature zone of the high-pressure hot water storage tank. The discharge modes include: The gas storage tank releases high-pressure air, which is then reduced to the pressure required at the inlet of the expander unit via a pressure regulating valve. The high-pressure air enters each stage of the reheater, exchanges heat with the hot water from the high-temperature zone, and then enters each stage of the expander to perform power generation. The hot water from each stage of the reheater returns to the low-temperature zone after releasing heat. The combined operation mode includes both charging and discharging conditions: During charging, the first-stage heat exchanger allocates all its heat for external heating, and the heating load is dynamically adjusted according to the heat user's demand. The heat supplied accounts for 30% to 50% of the total heat of the final stage compression. The second-stage heat exchanger allocates its heat for inlet preheating, and the preheating temperature is automatically adjusted according to the ambient temperature. When the ambient temperature is below 10°C, the inlet preheating is activated to preheat the inlet air temperature to 10 to 15°C. When the ambient temperature is above 15°C, the inlet preheating bypass is activated, and the preheater is taken out of operation. Under discharge conditions, the compressor stops running and cannot provide heat. Under these conditions, in addition to normal expansion and power generation, the hot water in the high-temperature zone of the high-pressure hot water storage tank releases some heat to external heat users through the heating bypass heat exchanger. The heating bypass flow rate does not exceed 20% of the total circulation flow rate of the storage tank.

[0016] Furthermore, the charging mode also includes: controlling the outlet flow rate of the circulating water pump and the water distribution uniformity of the upper water distributor, so that the heated hot water enters the high-temperature zone of the high-pressure hot water storage tank in a laminar flow state with a Reynolds number of less than 2000. The temperature distribution inside the high-pressure hot water storage tank is monitored in real time by the temperature sensor array. When the thickness of the thermal stratification transition zone exceeds 30% of the inner cavity height of the high-pressure hot water storage tank, the circulation flow rate is reduced or charging is paused, and charging continues after the stratification is restored. When multiple high-pressure hot water storage tanks are connected in parallel, the number of tanks put into operation is adjusted according to the discharge power demand and the heating load demand. The charging and discharging rate of each tank is controlled by an independent valve to keep the thermal stratification state of each tank balanced.

[0017] Furthermore, the joint operation mode also includes: dynamically adjusting the flow distribution ratio of each loop in the waste heat diversion heat exchanger through a heating-energy storage priority controller.

[0018] Beneficial effects: (1) The solution provided by this invention improves safety and reduces system cost. Replacing 400~600℃ high-temperature heat transfer oil or molten salt with 180℃ high-pressure hot water eliminates the risk of fire caused by high-temperature heat transfer oil leakage and the corrosion problem of molten salt on pipelines. The operating temperature of high-pressure hot water is lower than the creep temperature threshold of most structural materials, and the design margin of the pressure-bearing shell is sufficient. At the same time, it saves the cost of heat transfer oil procurement and waste oil treatment, and eliminates the need for electric heat tracing and anti-condensation measures in molten salt systems. Taking a 300MW power plant as an example, the cost of the thermal storage system as a percentage of the total investment can be reduced from 25%~30% of the high-temperature solution to 15%~20%.

[0019] (2) The solution provided by this invention is simple. By adopting a single-tank layered thermal storage architecture instead of the complex configuration of the traditional double-tank + gas connection pipe + external gas supply mechanism, the number of pipeline valves is reduced by about 30%, the auxiliary power consumption (external air compressor gas supply) is completely eliminated, and the floor area is 50%~60% of that of the double-tank solution. At the same time, the layered structure of the high-pressure hot water thermal storage tank, together with the guide plate and temperature monitoring, ensures that the temperature quality of the usable hot water in the tank remains stable during the charge and discharge cycle. The thickness of the thermal stratification transition zone can be controlled within 30% of the tank height, avoiding the reduction of effective thermal storage capacity caused by the mixing of hot and cold water. The high-pressure hot water storage tank of this invention has an internal structure consisting of a high-temperature zone, a thermal stratification transition zone, and a low-temperature zone from top to bottom. Furthermore, the tank incorporates an upper water distributor at the top, a lower water distributor at the bottom, and a horizontal baffle plate in the thermal stratification transition zone. This design enables simultaneous cooling and heating within a single tank, effectively saving system space and significantly reducing system equipment costs. In terms of efficiency, the partitioning of the high-temperature, thermal stratification transition, and low-temperature zones, along with the upper and lower water distributors and the horizontal baffle plate, significantly improves the stability of cooling and heating supply from the high-pressure hot water storage tank. This effectively enhances the heat exchange stability of the heat exchangers and reheaters in the system, which is crucial for maintaining long-term stable and efficient system operation.

[0020] (3) By setting up multiple high-pressure hot water storage tanks with the structure of the present invention, multiple independent heat storage tanks can be connected in parallel and can be flexibly switched according to load demand. The failure of a single tank does not affect the overall operation of the system, thus improving the availability of the power station.

[0021] (4) This invention reduces the types of working fluids in the system from the traditional three types (compressed air, high-pressure hot water, and high-pressure gas) to two types (compressed air and high-pressure hot water), eliminating the need for external gas supply mechanisms, gas connection pipes, and supporting control systems, thus significantly reducing the complexity of the system process. At the same time, the single-tank thermal stratification process replaces the double-tank water migration process, reducing the head requirement of the circulating water pump by about 15% to 20% (without needing to overcome the elevation difference of water between the two tanks and pipeline resistance), and correspondingly reducing pump power consumption.

[0022] (5) By setting up a waste heat diversion heat exchanger, the final stage compression heat is distributed in stages according to temperature grade: the highest temperature waste heat is used for external heating, the second highest temperature waste heat is used for inlet preheating (extremely cold conditions), and the remaining waste heat enters the thermal storage tank. This staged utilization strategy enables the system's overall energy efficiency (electricity + heat) to reach 75%~85%, which is about 13~20 percentage points higher than the single energy storage route (62%~65%). Under the joint operation mode, the proportion of heat extracted from the thermal storage tank by the heating bypass does not exceed 20%, ensuring that the discharge power decrease does not exceed 10%, achieving the optimal trade-off between heating revenue and power generation loss.

[0023] (6) The present invention also solves the problem of process coupling between the above-ground compression / expansion / heat storage system and the underground gas storage. When using salt caverns, the problem of the gas storage volume decreasing year by year due to salt rock creep needs to be considered, and the expansion interface of the heat storage tank group is reserved in the process. When using hard rock chambers, the sealing performance of steel lining or concrete lining needs to be considered to withstand the gas storage pressure fluctuation, and the gas storage pressure safety margin is set in the process.

[0024] (7) This invention selects 150~190℃ as the temperature window for the compressed air energy storage process system. If a heat storage temperature below 150℃ is selected, the expander inlet temperature will decrease accordingly, and the system's electro-electric conversion efficiency will decrease significantly. If a heat storage temperature above 200℃ is selected, the saturated vapor pressure of water will increase sharply (200℃ corresponds to a saturated pressure of about 1.55MPa), and the design pressure and cost of the storage tank will increase significantly. By selecting this temperature range, material costs and manufacturing difficulties can be controlled. Compared with the 180℃ mentioned in Reference 1, Reference 1 is a general technical solution for applying hot water heat storage to compressed air energy storage. This invention is a complete process solution that limits hot water heat storage to a specific medium-temperature window and completes the matching of process parameters for the entire system around this window. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the overall architecture of the large-capacity compressed air energy storage system of the present invention; Figure 2 This is a schematic cross-sectional view of the high-pressure hot water storage tank in the large-capacity compressed air energy storage system of the present invention. Figure 3 This is a schematic diagram of the external heating circuit process in the large-capacity compressed air energy storage system of the present invention; Figure 4 This is a schematic diagram of the inlet preheater loop process in the large-capacity compressed air energy storage system of the present invention; Figure 5 This is a schematic diagram of the operation method of the large-capacity compressed air energy storage system of the present invention; Figure 6 This is a schematic diagram of the allocation logic of the heating-energy storage priority controller in the large-capacity compressed air energy storage system of the present invention. Detailed Implementation

[0027] To better understand the technical solution of the present invention, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0028] It should be understood that the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0029] Example 1

[0030] A large-capacity compressed air energy storage system includes a high-pressure hot water storage tank. The high-pressure hot water storage tank adopts a single-tank layered heat storage architecture. From top to bottom, the interior of the high-pressure hot water storage tank consists of a high-temperature zone, a thermal stratification transition zone, and a low-temperature zone. The high-pressure hot water storage tank utilizes the saturated vapor pressure of the medium-temperature (150~190℃) high-pressure hot water within the tank to maintain the tank pressure, eliminating the need for an external air supply mechanism. The thermal stratification transition zone is equipped with a horizontal baffle plate to suppress longitudinal water flow disturbance to the water stratification and maintain thermal stratification. The high-temperature zone is equipped with an upper water distributor, and the low-temperature zone is equipped with a lower water distributor. The upper water distributor ensures uniform horizontal distribution of high-temperature water entering and exiting the high-temperature zone, and the lower water distributor ensures uniform horizontal distribution of low-temperature water entering and exiting the low-temperature zone. A temperature sensor array is uniformly arranged from bottom to top on the internal sidewall of the high-pressure hot water storage tank. The high-pressure hot water storage tank provides low-temperature water to the heat exchanger of the energy storage system or high-temperature water to the reheater.

[0031] Furthermore, the opening ratio of the horizontal guide plate is 25%~35%; the upper water distributor is composed of an upper annular porous tube, and the lower water distributor is composed of a lower annular porous tube. The two ends of the upper annular porous tube are respectively connected to the high-temperature water outlet and the high-temperature water inlet; the two ends of the lower annular porous tube are respectively connected to the low-temperature water outlet and the low-temperature water inlet; the energy storage system includes two or more high-pressure hot water storage tanks connected in parallel.

[0032] The high-pressure hot water storage tank used in this invention has an internal structure consisting of a high-temperature zone, a thermal stratification transition zone, and a low-temperature zone from top to bottom. Furthermore, the tank incorporates an upper water distributor at the top, a lower water distributor at the bottom, and a horizontal baffle plate in the thermal stratification transition zone. This design enables simultaneous cooling and heating within a single tank, effectively saving system space and significantly reducing system equipment costs. In terms of efficiency, the partitioning of the high-temperature, thermal stratification transition, and low-temperature zones, along with the upper and lower water distributors and the horizontal baffle plate, significantly improves the stability of cooling and heating supply from the high-pressure hot water storage tank. This also effectively enhances the heat exchange stability of the heat exchangers and reheaters in the system, which is crucial for maintaining long-term stable and efficient system operation.

[0033] Furthermore, the system also includes: A multi-stage compressor unit, wherein the multi-stage compressor unit consists of N compressors connected in series, where N≥3, and an intercooler is provided between each stage of compressors. The outlet of the final stage compressor is connected to the inlet of the underground gas storage tank through a compressed air main pipeline. The gas storage facility utilizes at least one underground space selected from salt caverns, hard rock chambers, or aquifers as the storage location for compressed air. Its effective storage volume meets the requirements of large-capacity (300MW and above) power plants for long-term (4 hours and above) full-power discharge. The operating pressure range of the gas storage facility is determined jointly by geological conditions and system design. A multi-stage expander unit, wherein the multi-stage expander unit consists of K stages of expanders connected in series, where K≥2, and a reheater is installed between each stage of expander. The inlet of the first stage expander is connected to the outlet of the underground gas storage tank via a pressure regulating valve group. The high-temperature water inlet is connected to the hot water side of the intermediate cooler through a high-pressure hot water circulation pipeline, and the high-temperature water outlet is connected to the hot water side of the reheater through a high-pressure hot water circulation pipeline, forming a hot water circulation loop under charging conditions and a hot water circulation loop under discharging conditions.

[0034] Furthermore, the energy storage system also includes a final-stage compression heat utilization subsystem, which includes a waste heat diversion heat exchanger installed at the outlet of the final-stage compressor. The waste heat diversion heat exchanger distributes the compression heat at the outlet of the final-stage compressor according to temperature grade to the external heating circuit, the inlet preheating circuit, and the high-pressure hot water storage circuit.

[0035] Furthermore, the high-temperature zone has a temperature of 150~190℃, and the low-temperature zone has a temperature of 40~60℃; the temperature sensor array has no fewer than 8 measuring points; and a level gauge is installed on one side of the tank to monitor the water level inside the tank.

[0036] Furthermore, when multiple high-pressure hot water storage tanks are operated in parallel, each tank is controlled to switch on and off via an independent valve, and the charging and discharging rates of each tank are independently adjusted; the gas storage tank and the expander unit are connected via a pressure regulating valve group, which is used to adjust the pressure changes in the gas storage tank and the stability of the inlet pressure of the expander unit.

[0037] Furthermore, the waste heat diversion heat exchanger includes a three-stage heat exchanger group connected in series, namely a first-stage heat exchanger, a second-stage heat exchanger, and a third-stage heat exchanger, wherein: The hot-side inlet of the first-stage heat exchanger is connected to the outlet of the final-stage compressor, the hot-side outlet of the first-stage heat exchanger is connected to the hot-side inlet of the second-stage heat exchanger, and the cold side of the first-stage heat exchanger is connected to the external heating circuit. The hot-side outlet of the second-stage heat exchanger is connected to the hot-side inlet of the third-stage heat exchanger. The cold side of the second-stage heat exchanger is connected to the inlet preheating circuit. An inlet preheater is installed at the beginning of the inlet preheating circuit and is arranged on the inlet duct of the first-stage compressor. The hot-side outlet of the third-stage heat exchanger is connected to the inlet of the gas storage tank via a pipeline, and the cold-side outlet of the third-stage heat exchanger is connected to the high-temperature water inlet of the high-pressure hot water storage tank.

[0038] An operation method for the above-mentioned energy storage system, the operation method including a charging mode, a discharging mode and a combined operation mode; The charging modes include: The compressors at each stage compress the air step by step; the intercoolers at each stage transfer the heat of compression between stages to the high-pressure hot water circuit; the heated high-pressure hot water flows into the high-temperature zone at the top of the high-pressure hot water storage tank; the return water from the low-temperature zone at the bottom of the storage tank is sent back to the cold water side of the intercoolers at each stage by the circulation pump to form a cycle; the high-pressure air after the final stage compression is sent to the underground gas storage through pipelines. In charging mode, the high-temperature compressed air from the outlet of the final stage compressor enters the waste heat diversion heat exchanger and is distributed in three stages according to temperature grade: the highest temperature part is released to external heat users through the heating heat exchanger; the second highest temperature part is preheated to the ambient air entering the first stage compressor through the inlet preheater in the inlet preheating circuit; the remaining heat is combined with the hot water side outlet of each stage intermediate cooler and flows into the high-temperature zone of the high-pressure hot water storage tank. The discharge modes include: The gas storage tank releases high-pressure air, which is then reduced to the pressure required at the inlet of the expander unit via a pressure regulating valve. The high-pressure air enters each stage of the reheater, exchanges heat with the hot water from the high-temperature zone, and then enters each stage of the expander to perform power generation. The hot water from each stage of the reheater returns to the low-temperature zone after releasing heat. The air after the final stage of expansion is discharged into the atmosphere. The combined operation mode includes both charging and discharging conditions: During periods of heating demand (such as the winter heating season), the system operates in combined mode: During charging, the first-stage heat exchanger allocates all its heat for external heating, and the heating load is dynamically adjusted according to the heat user's demand. The heat supplied accounts for 30% to 50% of the total heat of the final stage compression. The second-stage heat exchanger allocates its heat for inlet preheating, and the preheating temperature is automatically adjusted according to the ambient temperature. When the ambient temperature is below 10°C, the inlet preheating is activated to preheat the inlet air temperature to 10 to 15°C. When the ambient temperature is above 15°C, the inlet preheating bypass is activated, and the preheater is taken out of operation. Under discharge conditions, the compressor stops running and cannot provide heat. Under these conditions, in addition to normal expansion and power generation, the hot water in the high-temperature zone of the high-pressure hot water storage tank releases some heat to external heat users through the heating bypass heat exchanger. The heating bypass flow rate does not exceed 20% of the total circulation flow rate of the storage tank, ensuring that the discharge power decreases by no more than 10%.

[0039] In the combined operation mode, the system dynamically allocates charging and discharging power and heat supply according to the grid dispatch instructions and heat load demand instructions, so as to maximize the comprehensive energy efficiency of power-heat combined supply.

[0040] Furthermore, the charging mode also includes: controlling the outlet flow rate of the circulating water pump and the water distribution uniformity of the upper water distributor, so that the heated hot water enters the high-temperature zone of the high-pressure hot water storage tank in a laminar flow state with a Reynolds number of less than 2000. The temperature distribution inside the high-pressure hot water storage tank is monitored in real time by the temperature sensor array. When the thickness of the thermal stratification transition zone exceeds 30% of the inner cavity height of the high-pressure hot water storage tank, the circulation flow rate is reduced or charging is paused, and charging continues after the stratification is restored. The discharge mode also includes: controlling the flow rate of water taken from the high-temperature zone of the heat storage tank and the uniformity of the water intake distribution, so that the cooled water returns to the low-temperature zone of the heat storage tank at a low flow rate. When multiple high-pressure hot water storage tanks are connected in parallel, the number of tanks put into operation is adjusted according to the discharge power demand and the heating load demand. The charging and discharging rate of each tank is controlled by an independent valve to keep the thermal stratification state of each tank balanced.

[0041] Furthermore, the joint operation mode also includes: dynamically adjusting the flow distribution ratio of each loop in the waste heat diversion heat exchanger through a heating-energy storage priority controller, specifically including: Read power grid dispatch instructions and thermal power load demand instructions; When the heating load command is greater than zero and the ambient temperature is lower than 10℃, the flow distribution ratio of the external heating circuit in the waste heat diversion heat exchanger will be increased to no less than 50%. When the ambient temperature is below 0℃, the flow distribution ratio of the inlet preheating circuit is fixed at 25% and does not participate in dynamic adjustment. When the ambient temperature is not lower than 15℃, the system operates in pure energy storage mode, distributing all the heat from the final stage compression to the high-pressure hot water heat storage circuit, while bypassing the external heating circuit and the inlet preheating circuit.

[0042] Example 2

[0043] This invention provides a large-capacity compressed air energy storage system and method, specifically including: A multi-stage compressor unit consists of N compressors connected in series (N≥3). Intercoolers are installed between each stage of the compressor. The outlet of the final stage compressor is connected to the inlet of the underground gas storage tank through a compressed air main pipeline. The high-pressure hot water thermal storage system consists of M high-pressure hot water thermal storage tanks connected in parallel (M≥2). Each tank employs a single-tank layered thermal storage structure, with a high-temperature zone at the top, a thermal stratification transition zone in the middle, and a low-temperature zone at the bottom. The internal pressure of each tank is maintained by the saturated vapor pressure of the medium-temperature (150~190℃) high-pressure hot water itself, eliminating the need for an external gas supply mechanism. A thermal stratification maintenance device is installed within each high-pressure hot water thermal storage tank. This device includes a horizontal guide plate located in the thermal stratification transition zone and a temperature sensor array uniformly arranged along the height of the tank. The underground gas storage facility utilizes at least one of the following underground spaces as the storage location for compressed air: salt caverns, hard rock chambers, or aquifers. The effective storage volume meets the requirements of large-capacity (300MW and above) power plants for long-term (4 hours and above) full-power discharge. The operating pressure range of the gas storage facility is determined jointly by geological conditions and system design. The multi-stage expander unit consists of K-stage expanders connected in series (K≥2), with reheaters installed between each stage of expander. The inlet of the first-stage expander is connected to the outlet of the underground gas storage tank via a pressure regulating valve group. The high-temperature water inlet and outlet of the high-pressure hot water storage tank is connected to the hot water side of the intermediate cooler (interstage heat exchanger) and the hot water side of the reheater through high-pressure hot water circulation pipelines, forming a hot water circulation loop under charging conditions and a hot water circulation loop under discharging conditions. The system also includes a final-stage compression heat grading and utilization system, which includes a waste heat diversion heat exchanger installed at the outlet of the final-stage compressor. The waste heat diversion heat exchanger distributes the compression heat at the outlet of the final-stage compressor according to temperature grade to the external heating circuit, the inlet preheating circuit, and the high-pressure hot water storage circuit.

[0044] Furthermore, the pressure-bearing shell of the high-pressure hot water storage tank is designed to withstand a pressure of not less than 2.0 MPa, and is made of boiler steel plate or pressure vessel steel that is resistant to high temperature and pressure. The temperature of the upper high-temperature zone inside the tank is approximately 150~190℃, and the temperature of the lower low-temperature zone is approximately 40~60℃. High-temperature water inlet and outlet and low-temperature water inlet and outlet are respectively provided at the top and bottom of the tank. The opening ratio of the horizontal guide plate is 25%~35%, and the number of measuring points of the temperature sensor array is not less than 8. A safety valve is installed at the top of the tank, with a set pressure not exceeding 2.0 MPa. A level gauge is installed on the left side of the tank to monitor the water level inside the tank.

[0045] Furthermore, the high-pressure hot water storage tank is equipped with an upper water distributor and a lower water distributor. The upper water distributor is located at the top of the high-temperature zone, and the lower water distributor is located at the bottom of the low-temperature zone. The water distributor has a ring-shaped porous pipe structure, which makes the inlet and outlet water evenly distributed on the horizontal plane. When multiple high-pressure hot water storage tanks are connected in parallel, each tank is controlled by an independent valve to switch on and off, and the charging and discharging rates of each tank are adjusted independently.

[0046] Furthermore, the gas storage tank and the expander unit are connected by a pressure regulating valve group, which is used to adjust the pressure changes in the underground gas storage tank and the stability of the inlet pressure of the expander unit.

[0047] Furthermore, the waste heat diversion heat exchanger comprises a three-stage heat exchanger group connected in series, wherein: The hot-side inlet of the first-stage heat exchanger is connected to the outlet of the final-stage compressor, the hot-side outlet of the first-stage heat exchanger is connected to the hot-side inlet of the second-stage heat exchanger, and the cold side of the first-stage heat exchanger is connected to the external heating circuit. The hot-side outlet of the second-stage heat exchanger is connected to the hot-side inlet of the third-stage heat exchanger. The cold side of the second-stage heat exchanger is connected to the inlet preheating circuit. An inlet preheater is installed at the beginning of the inlet preheating circuit and is arranged on the inlet duct of the first-stage compressor. The hot-side outlet of the third-stage heat exchanger is connected to the inlet of the underground gas storage tank via a pipeline, and the cold-side outlet of the third-stage heat exchanger is connected to the high-temperature zone inlet of the high-pressure hot water storage tank.

[0048] Furthermore, the external heating circuit includes a heating circulation pump, a heating heat exchanger, and a heating regulating valve. The hot side inlet of the heating heat exchanger is connected to the first-stage cold side outlet of the waste heat diversion heat exchanger. The heating regulating valve automatically adjusts the flow rate of the heating hot water according to the feedback signal of the heating return water temperature. The system also includes a heating bypass heat exchanger, the hot side inlet of which is connected to the high-temperature zone outlet of the high-pressure hot water storage tank, and the heating bypass flow rate does not exceed 20% of the total circulation flow rate of the storage tank.

[0049] Furthermore, the inlet preheater is a shell-and-tube heat exchanger. The temperature of the preheated air is regulated by mixing it with ambient air through a mixing valve to ensure that the air temperature entering the first-stage compressor is not lower than 10°C (to prevent freezing in winter) and does not exceed 25°C (to avoid excessive increase in compression power consumption). When the ambient temperature is below 10°C, the inlet preheater is activated to preheat the air entering the first-stage compressor to 10~15°C; when the ambient temperature is above 15°C, the inlet preheater is bypassed and deactivated.

[0050] An operation method for a high-pressure hot water thermal storage type medium-temperature insulated compressed air energy storage system, using the above-mentioned energy storage system, characterized in that it includes a charging mode, a discharging mode, and a combined operation (charging + heating) mode. The charging modes include: The compressors at each stage compress the air step by step; the intercoolers at each stage transfer the heat of compression between stages to the high-pressure hot water circuit; the heated high-pressure hot water flows into the high-temperature zone at the top of the high-pressure hot water storage tank; the return water from the low-temperature zone at the bottom of the storage tank is sent back to the cold water side of the intercoolers at each stage by the circulation pump to form a cycle; the high-pressure air after the final stage compression is sent to the underground gas storage through pipelines. In charging mode, the high-temperature compressed air from the outlet of the final compressor enters the waste heat diversion heat exchanger and is distributed in three stages according to temperature grade: the highest temperature part is released to external heat users through the heating heat exchanger; the second highest temperature part is preheated to the ambient air entering the first compressor through the inlet preheater; the remaining heat is combined with the hot water side outlet of each stage of the intermediate cooler and flows into the high-temperature zone at the top of the high-pressure hot water storage tank. The discharge modes include: The underground gas storage facility releases high-pressure air, which is then reduced to the pressure required at the inlet of the expander unit via a pressure regulating valve. The high-pressure air enters each stage of the reheater, where it exchanges heat with the hot water from the high-temperature zone at the top of the high-pressure hot water storage tank before entering each stage of the expander to generate electricity. The hot water from each stage of the reheater returns to the low-temperature zone at the bottom of the high-pressure hot water storage tank after releasing heat. The air after the final stage of expansion is discharged into the atmosphere. The joint operation mode includes: During periods of heating demand (such as the winter heating season), the system operates in combined mode: Under charging conditions, all the heat distributed in the first stage of the final compression heat is used for external heating. The heating load is dynamically adjusted according to the heat user's demand, and the heating heat accounts for 30% to 50% of the total heat of the final compression heat. During charging, the second stage of heat distribution from the final stage compression heat is used for inlet preheating. The preheating temperature is automatically adjusted according to the ambient temperature. When the ambient temperature is below 10℃, the inlet preheating is activated to preheat the inlet air temperature to 10~15℃. When the ambient temperature is above 15℃, the inlet preheating bypass is activated, and the preheater is taken out of operation. Under discharge conditions, the compressor stops operating and cannot provide heat. In this condition, in addition to normal expansion and power generation, the high-temperature zone hot water in the high-pressure hot water storage tank can release some heat to external heat users through the heating bypass heat exchanger. The heating bypass flow rate does not exceed 20% of the total circulation flow rate of the storage tank, ensuring that the discharge power decrease does not exceed 10%. In the combined operation mode, the system dynamically allocates charging and discharging power and heat supply according to the grid dispatch instructions and heat load demand instructions, so as to maximize the comprehensive energy efficiency of power-heat combined supply.

[0051] Furthermore, in the charging mode, the outlet flow rate of the circulating water pump and the water distribution uniformity of the water distributor are controlled so that the heated hot water enters the high-temperature zone of the heat storage tank in a laminar flow state with a Reynolds number of less than 2000. The temperature distribution inside the thermal storage tank is monitored in real time by a temperature sensor array. When the thickness of the thermal stratification transition zone exceeds 30% of the tank height, the circulation flow rate is reduced or charging is paused, and charging continues after the stratification is restored.

[0052] Furthermore, in the discharge mode, the flow rate of water taken from the high-temperature zone of the heat storage tank and the uniformity of the water intake distribution are controlled so that the cooled water returns smoothly to the low-temperature zone of the heat storage tank at a low flow rate. When multiple high-pressure hot water storage tanks are connected in parallel, the number of tanks put into operation is determined according to the discharge power demand and the heating load demand. The charging and discharging rate of each tank is controlled by an independent valve to keep the thermal stratification state of each tank balanced.

[0053] Furthermore, in the combined operation mode, the system also includes a heating-energy storage priority controller, which dynamically adjusts the flow distribution ratio of each loop in the waste heat diversion heat exchanger. Read power grid dispatch instructions and thermal power load demand instructions; When the heating load command is greater than zero and the ambient temperature is lower than 10℃, the flow distribution ratio of the external heating circuit in the waste heat diversion heat exchanger will be increased to no less than 50%. When the ambient temperature is below 0℃, the flow distribution ratio of the inlet preheating circuit is fixed at 25% and does not participate in dynamic adjustment. When the ambient temperature is not lower than 15℃, the system operates in pure energy storage mode, distributing all the heat from the final stage compression to the high-pressure hot water heat storage circuit, while bypassing the external heating circuit and the inlet preheating circuit.

[0054] Example 3

[0055] refer to Figure 1 This invention provides a 300MW-class compressed air energy storage system, specifically comprising: The system includes a 3-stage axial-flow + centrifugal combined compressor unit, a thermal storage tank unit consisting of a high-pressure hot water storage tank, a salt cavern type underground gas storage facility, a 2-stage expander unit, and supporting working fluid delivery pipelines, valve groups, circulating water pumps, and control systems.

[0056] Parameters for each stage of the compressor: First-stage pressure ratio approximately 2.5, final-stage outlet pressure approximately 8 MPa, outlet temperature approximately 190℃. A shell-and-tube intercooler is installed between each stage; compressed air flows through the shell side, and high-pressure hot water flows through the tube side. The intercooler's tube-side design pressure is 2.0 MPa.

[0057] The gas storage facility is a salt cavern type with an effective volume of approximately 1.5 million cubic meters and an operating pressure range of 4.5 to 8.0 MPa.

[0058] Expander parameters for each stage: First-stage inlet pressure approximately 7.5 MPa (after pressure regulation), last-stage outlet pressure approximately 0.1 MPa. A shell-and-tube reheater is installed between stages; high-pressure air flows through the shell side, and high-pressure hot water flows through the tube side. The reheater tube-side design pressure is 2.0 MPa.

[0059] refer to Figure 1 The invention further includes a final-stage compression heat grading and utilization system, which includes a waste heat diversion heat exchanger installed at the outlet of the final-stage compressor. This waste heat diversion heat exchanger gradingly distributes the compression heat from the final-stage compressor outlet to the external heating circuit, the inlet preheating circuit, and the high-pressure hot water storage circuit according to temperature grade. A three-stage series heat exchanger assembly is used. First stage (heating): The hot-side inlet of the first-stage heat exchanger is connected to the outlet of the final-stage compressor, and the hot-side outlet of the first-stage heat exchanger is connected to the hot-side inlet of the second-stage heat exchanger. The cold side of the first-stage heat exchanger is connected to the external heating circuit. The inlet air temperature of the first-stage heat exchanger is 190℃, and the outlet air temperature is 140℃; the inlet temperature of the heating return water is 60℃, and the outlet temperature is 110℃; the heat exchange capacity accounts for approximately 40% of the heat exchanged during the final stage compression. Second stage (inlet waste heat): The hot-side outlet of the second-stage heat exchanger is connected to the hot-side inlet of the third-stage heat exchanger. The cold side of the second-stage heat exchanger is connected to the inlet preheating circuit. An inlet preheater is installed at the beginning of the inlet preheating circuit, and the inlet preheater is arranged on the inlet duct of the first-stage compressor. The inlet air temperature of the second-stage heat exchanger is 140°C, and the outlet air temperature is 90°C; the ambient air inlet temperature is -1030°C, and the outlet temperature is 525°C; the heat exchange accounts for approximately 25% of the final stage compression heat. The third stage (heat storage tank): The hot-side outlet of the third-stage heat exchanger is connected to the inlet of the underground gas storage tank via a pipeline, and the cold-side outlet of the third-stage heat exchanger is connected to the high-temperature zone inlet of the high-pressure hot water heat storage tank. The inlet air temperature of the third-stage heat exchanger is 90°C, and the outlet air temperature is 45°C; the return water inlet temperature of the heat storage tank is 50°C, and the outlet temperature is 120°C; the heat exchange accounts for approximately 35% of the final stage compression heat.

[0060] refer to Figure 2 Each thermal storage tank is a vertical cylindrical pressure vessel with an inner diameter of 4m, a height of 12m, and an effective volume of approximately 150m³. 3 The tank body is made of Q345R (steel for boilers and pressure vessels), and the wall thickness is determined by calculation to meet the design pressure of 2.0MPa and design temperature of 200℃. The tank body is covered with an external insulation layer (alumina silicate fiber felt, 150mm thick), with an external surface temperature ≤50℃.

[0061] Internal structure of the tank (from top to bottom): The top high-temperature water inlet and outlet connect to the upper high-temperature zone (150~190℃). The upper water distributor (annular perforated pipe) ensures that the inlet and outlet water are evenly distributed on the horizontal plane. The central horizontal guide plate (approximately 30% opening ratio, 10mm aperture) is located in the thermal stratification transition zone and is used to suppress longitudinal flow disturbance to stratification. The lower water distributor is located in the low-temperature zone (approximately 40~60℃). Bottom low-temperature water inlet and outlet (DN200).

[0062] Eight temperature measuring points (spaced approximately 1.5m apart) are evenly arranged along the height of the tank wall, along with a level gauge, and a spring-loaded full-opening safety valve (set pressure 2.0MPa) is installed on the top of the tank.

[0063] refer to Figure 3 The external heating circuit includes a heating circulation pump, a heating heat exchanger, and a heating regulating valve. The hot-side inlet of the heating heat exchanger is connected to the first-stage cold-side outlet of the waste heat diversion heat exchanger. The heating heat exchanger is a shell-and-tube type, with the return water flowing through the shell side and the hot water (110℃) from the first-stage plate heat exchanger flowing through the tube side. The heating load is adjusted according to the heat user's demand, with a maximum heating load of approximately 30MW (accounting for 10% of the charging power). The heating circulation pump has a head of approximately 32m and a flow rate of approximately 520m³ / h. 3 / h. The heating regulating valve automatically adjusts its opening degree based on the feedback signal of the heating return water temperature to control the flow rate of heating hot water.

[0064] The system also includes a heating bypass heat exchanger, the hot side inlet of which is connected to the high-temperature zone outlet of the high-pressure hot water storage tank, and the heating bypass flow rate does not exceed 20% of the total circulation flow rate of the storage tank.

[0065] refer to Figure 1 and Figure 4 The inlet preheater circuit uses a tube-fin heat exchanger located within the inlet duct of the primary compressor. It operates when the ambient temperature is below 5°C in winter, preheating the inlet air temperature to 5-10°C; it bypasses and deactivates when the ambient temperature is above 15°C in summer. The preheated air temperature is precisely controlled by mixing with ambient air via a mixing valve, with a control accuracy of ±1°C. Inlet preheating reduces the auxiliary heating power consumption of the compressor by approximately 0.5MW during winter startup, while also preventing cylinder condensation problems caused by excessively low inlet air temperature.

[0066] refer to Figure 5 The present invention also provides an operating method, including a charging mode, a discharging mode and a combined operation (charging + heating) mode; In the charging mode, the four-stage compressor operates sequentially. An electric motor from the power grid drives each stage of the compressor. Atmospheric air is compressed to approximately 0.25 MPa and 150°C in the first stage before entering the first-stage intercooler. There, it exchanges heat with approximately 50°C return water from the low-temperature zone of the thermal storage tank, cooling the air to approximately 45°C. The hot water then heats up to approximately 170°C before flowing into the high-temperature zone at the top of the thermal storage tank. This process continues, with the compressed air reaching approximately 8 MPa and 45°C at the final stage outlet, before being piped into the underground salt cavern gas storage facility.

[0067] Meanwhile, the return water from the low-temperature zone at the bottom of the thermal storage tank is pumped into the cold water side of each stage of the intercooler via a circulating water pump, completing a closed-loop circulation. The circulating water flow rate is regulated by a variable frequency pump to stabilize the hot water outlet temperature of each stage of the intercooler at 170~180℃.

[0068] In the discharge mode, high-pressure air is released from the salt cavern gas storage tank, reduced to approximately 7.5 MPa by a pressure regulating valve group, and then sent to the first-stage reheater. High-pressure hot water at approximately 180°C in the upper high-temperature zone of the heat storage tank is sent to the tube side of the first-stage reheater via pipelines and a circulating water pump. The high-pressure air on the shell side is heated to approximately 170°C and then enters the first-stage expander to perform work, driving the generator to generate electricity.

[0069] The air pressure at the outlet of the first-stage expander is approximately 2.5 MPa, and the temperature is approximately 80°C. It then enters the second-stage reheater and exchanges heat again with 180°C hot water, raising its temperature to approximately 170°C before entering the second-stage expander. This process continues until, after four stages of expansion and three stages of interstage reheating, the air pressure at the outlet of the final-stage expander is approximately 0.1 MPa, and the temperature is approximately 50°C, at which point it is discharged into the atmosphere.

[0070] The reheated water temperature is about 50~60℃, and it returns to the low-temperature zone at the bottom of the heat storage tank through pipelines.

[0071] The combined operation mode is used when heating demand exists (winter heating season). Under charging conditions, all the heat distributed in the first stage of the final compression heat is used for external heating. The heating load is dynamically adjusted according to the heat user's demand, and the heating heat accounts for 30% to 50% of the total heat of the final compression heat. During charging, the second stage of heat distribution from the final stage compression heat is used for inlet preheating. In winter, when the ambient temperature is below 10℃, inlet preheating is activated to preheat the inlet air temperature to 10~15℃. In summer, when the ambient temperature is above 15℃, the inlet preheating bypass is activated and the preheater is taken out of operation. Under discharge conditions, the compressor stops operating and cannot provide heat. In this condition, in addition to normal expansion and power generation, the high-temperature zone hot water in the high-pressure hot water storage tank can release some heat to external heat users through the heating bypass heat exchanger. The heating bypass flow rate does not exceed 20% of the total circulation flow rate of the storage tank, ensuring that the discharge power decrease does not exceed 10%. In the combined operation mode, the system dynamically allocates charging and discharging power and heat supply according to the grid dispatch instructions and heat load demand instructions, so as to maximize the comprehensive energy efficiency of power-heat combined supply.

[0072] refer to Figure 6 The present invention also provides a heating-energy storage priority controller, specifically, Read the current power grid dispatch command (charging power command P_charge) and heat and power load demand command (heating load command Q_heat); Determine heating priority -- When the heating load command Q_heat > 0 and the ambient temperature <10℃ (heating season), the heating priority is increased, the heat exchange allocation ratio of the first-stage heat exchanger (heating stage) is increased to 50%, the heat exchange allocation ratio of the second-stage heat exchanger is fixed at 25%, and the allocation ratio of the third-stage heat exchanger is reduced accordingly. Under normal operating conditions (non-heating season, ambient temperature ≥10℃), all the heat from the final stage compression is distributed to the third stage heat exchanger, the first and second stages are bypassed, and the system operates in pure energy storage mode. Under discharge conditions, when heat load demand exists, no more than 20% of the flow rate of bypass hot water is drawn from the high-temperature zone of the high-pressure hot water storage tank and enters the heating bypass heat exchanger. The returned water after heat release returns to the low-temperature zone of the storage tank. The flow rate of the heating bypass is independently controlled by the heating regulating valve according to the heat load demand, without affecting the main process of expansion power generation.

[0073] Example 4

[0074] This example uses a 600MW / 2400MWh compressed air energy storage power station to illustrate the specific implementation process. Typical meteorological conditions: extreme minimum temperature in winter is -18℃, maximum temperature in summer is 38℃, the heating season is from November 15th to March 15th of the following year (120 days in total), and the non-heating season is 245 days.

[0075] The system consists of 4 rows of compressors, 4 rows of expanders, and 12 hot water storage tanks. It also utilizes a salt cavern gas storage facility to analyze the operation under different modes.

[0076] (1) Charging mode (pure energy storage, non-heating season) With an ambient temperature of 22℃ (summer) and no heating demand, the system operates from 00:00 to 06:00 for 6 hours. At 22℃, the system enters pure energy storage sub-mode: the inlet preheater bypass is disabled, and the heating heat exchanger is shut down; the exhaust gas from the final compressor (approximately 190℃) enters the waste heat diversion heat exchanger, and both the first stage (heating stage) and the second stage (inlet preheating stage) are bypassed, with 100% of the waste heat being sent to the heat storage tank; the compression heat from the intercoolers in stages 1-3 is also entirely sent to the tank. With the heat storage tank fully engaged, the total flow rate of the circulating water pump is 1440 m³ / h. 3 / h, approximately 120m³ per tank 3 / h; the temperature in the high-temperature zone of the thermal storage tank gradually increases from 50℃ to approximately 178℃. The underground gas storage tank is charged from 4.5MPa to 8.0MPa, with the charging volume sufficient for 4 hours of full-power discharge. For relevant parameter values ​​during charging, please refer to Table 1.

[0077] Table 1. Relevant parameter values ​​under charging mode

[0078] (2) Discharge mode (pure power generation, non-heating season) The ambient temperature was 20℃ (summer), with no heating demand. Operation occurred during peak grid hours from 9:00 AM to 1:00 PM, lasting 4 hours. The compressor was shut down, and both the waste heat diversion heat exchanger and the heating bypass heat exchanger were closed. Gas was drawn from the underground storage tank, and the pressure was reduced from 8.0 MPa to 7.5 MPa by the pressure regulating valve group before entering the first-stage expander. Hot water at 178℃ in the high-temperature zone of the thermal storage tank heated the extracted air (approximately 35℃) to 170℃ through various reheaters. This heated air then passed through four stages of expanders to generate electricity, with a total output of 600MW. After releasing heat, the hot water cooled to approximately 55℃ and returned to the low-temperature zone of the thermal storage tank. The thermal stratification transition zone was approximately 2.1m thick, satisfying laminar flow constraints. After 4 hours of discharge, the pressure in the gas storage tank dropped to 4.5 MPa, and the temperature in the high-temperature zone of the thermal storage tank dropped to approximately 155℃. Relevant parameter values ​​during discharge mode are shown in Table 2.

[0079] Table 2. Values ​​of relevant parameters under discharge mode.

[0080] (3) Joint operation mode (energy storage + heating, heating season) Ambient temperature -8℃, grid off-peak hours (00:00~05:00) for 5 hours, grid peak hours (09:00~13:00), discharge power 600MW for 4 hours, continuous heating, demand approximately 50MW, heating return water 55℃, heating area approximately 1.2 million m² 2 .

[0081] Operation status during the charging phase (00:00~05:00): With an ambient temperature of -8℃, the inlet preheater automatically engages, preheating the inlet air of the first-stage compressor from -8℃ to approximately 5℃, with the mixing air valve regulating accordingly. The exhaust gas from the final-stage compressor (approximately 190℃) is distributed via a waste heat diversion heat exchanger according to the following distribution: 50% for the first stage (heating), 25% for the second stage (inlet preheating), and 25% for the third stage (heat storage tank). All the compression heat from the first to third-stage intercoolers is fed into the tank. The external heat exchanger outputs approximately 50MW, with the return water from 55℃ to 90℃ delivered to users. The high-temperature zone of the heat storage tank is raised from 165℃ to approximately 178℃.

[0082] Operation status during the discharge phase (09:00~13:00): The compressor stops, and the waste heat diversion heat exchanger is deactivated; heating is switched to the heating bypass heat exchanger, drawing approximately 240m³ of heat from the high-temperature zone of the heat storage tank. 3 The hot water supply (≤20% of the total circulation flow) continues to supply heat for approximately 45MW; the thermal storage tank simultaneously supplies heat to the reheaters at each stage of the expander, resulting in a net output of approximately 570MW out of the 600MW power generation capacity (approximately 30MW equivalent to bypass heating). The high-temperature zone of the thermal storage tank has been reduced from 178℃ to approximately 160℃.

[0083] Based on a 120-day heating season, with one charge and one discharge per day, the overall energy efficiency is approximately 79%.

[0084] Under this joint operation mode, the proportion of heat extracted from the heat storage tank by the heating bypass does not exceed 20%, ensuring that the discharge power decreases by no more than 10%, thus achieving the optimal balance between heating revenue and power generation loss.

[0085] The embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A large-capacity compressed air energy storage system, characterized in that, The system includes a high-pressure hot water storage tank, which adopts a single-tank layered thermal storage architecture. The interior of the high-pressure hot water storage tank, from top to bottom, consists of a high-temperature zone, a thermal stratification transition zone, and a low-temperature zone. The thermal stratification transition zone is equipped with horizontal baffles to suppress disturbances to the water stratification caused by longitudinal water flow, thus maintaining thermal stratification. The high-temperature zone is equipped with an upper water distributor, and the low-temperature zone is equipped with a lower water distributor. The upper water distributor ensures that the high-temperature water entering and exiting the high-temperature zone is evenly distributed horizontally, and the lower water distributor ensures that the low-temperature water entering and exiting the low-temperature zone is evenly distributed horizontally. Temperature sensor arrays are evenly arranged on the internal sidewalls of the high-pressure hot water storage tank from bottom to top. The high-pressure hot water storage tank is used to provide low-temperature water to the heat exchanger of the energy storage system or high-temperature water to the reheater.

2. The energy storage system according to claim 1, characterized in that, The horizontal guide plate has an opening ratio of 25% to 35%; the upper water distributor is composed of an upper annular porous tube, and the lower water distributor is composed of a lower annular porous tube. The two ends of the upper annular porous tube are respectively connected to the high-temperature water outlet and the high-temperature water inlet; the two ends of the lower annular porous tube are respectively connected to the low-temperature water outlet and the low-temperature water inlet; the energy storage system includes two or more high-pressure hot water storage tanks connected in parallel.

3. The energy storage system according to claim 2, characterized in that, The system also includes: A multi-stage compressor unit, wherein the multi-stage compressor unit consists of N compressors connected in series, where N≥3, and an intercooler is provided between each stage of compressors. The outlet of the final stage compressor is connected to the inlet of the underground gas storage tank through a compressed air main pipeline. The gas storage facility uses at least one underground space selected from salt caverns, hard rock chambers, or aquifers as the storage location for compressed air. A multi-stage expander unit, wherein the multi-stage expander unit consists of K stages of expanders connected in series, where K≥2, and a reheater is installed between each stage of expander. The inlet of the first stage expander is connected to the outlet of the underground gas storage tank via a pressure regulating valve group. The high-temperature water inlet is connected to the hot water side of the intercooler via a high-pressure hot water circulation pipeline, and the high-temperature water outlet is connected to the hot water side of the reheater via a high-pressure hot water circulation pipeline.

4. The energy storage system according to claim 3, characterized in that, The energy storage system also includes a final-stage compression heat utilization subsystem, which includes a waste heat diversion heat exchanger installed at the outlet of the final-stage compressor. The waste heat diversion heat exchanger distributes the compression heat at the outlet of the final-stage compressor to the external heating circuit, the inlet preheating circuit, and the high-pressure hot water storage circuit according to the temperature grade.

5. The energy storage system according to claim 4, characterized in that, The high-temperature zone has a temperature of 150~190℃, and the low-temperature zone has a temperature of 40~60℃; the temperature sensor array has no fewer than 8 measuring points; a level gauge is installed on one side of the tank to monitor the water level inside the tank.

6. The energy storage system according to claim 5, characterized in that, When multiple high-pressure hot water storage tanks are connected in parallel, each tank is controlled to switch on and off via an independent valve, and the charging and discharging rates of each tank are adjusted independently. The gas storage tank and the expander unit are connected via a pressure regulating valve group, which is used to adjust the pressure changes in the gas storage tank and the stability of the inlet pressure of the expander unit.

7. The energy storage system according to claim 6, characterized in that, The waste heat diversion heat exchanger comprises a three-stage heat exchanger group connected in series, namely a first-stage heat exchanger, a second-stage heat exchanger, and a third-stage heat exchanger, wherein: The hot-side inlet of the first-stage heat exchanger is connected to the outlet of the final-stage compressor, the hot-side outlet of the first-stage heat exchanger is connected to the hot-side inlet of the second-stage heat exchanger, and the cold side of the first-stage heat exchanger is connected to the external heating circuit. The hot-side outlet of the second-stage heat exchanger is connected to the hot-side inlet of the third-stage heat exchanger. The cold side of the second-stage heat exchanger is connected to the inlet preheating circuit. An inlet preheater is installed at the beginning of the inlet preheating circuit and is arranged on the inlet duct of the first-stage compressor. The hot-side outlet of the third-stage heat exchanger is connected to the inlet of the gas storage tank via a pipeline, and the cold-side outlet of the third-stage heat exchanger is connected to the high-temperature water inlet of the high-pressure hot water storage tank.

8. A method for operating an energy storage system as described in any one of claims 1-7, characterized in that, The operating method includes charging mode, discharging mode, and combined operating mode; The charging modes include: In charging mode, the high-temperature compressed air from the outlet of the final stage compressor enters the waste heat diversion heat exchanger and is distributed in three stages according to temperature grade: the highest temperature part is released to external heat users through the heating heat exchanger; the second highest temperature part is preheated to the ambient air entering the first stage compressor through the inlet preheater in the inlet preheating circuit; the remaining heat is combined with the hot water side outlet of each stage intermediate cooler and flows into the high-temperature zone of the high-pressure hot water storage tank. The discharge modes include: The gas storage tank releases high-pressure air, which is then reduced to the pressure required at the inlet of the expander unit via a pressure regulating valve. The high-pressure air enters each stage of the reheater, exchanges heat with the hot water from the high-temperature zone, and then enters each stage of the expander to perform power generation. The hot water from each stage of the reheater returns to the low-temperature zone after releasing heat. The combined operation mode includes both charging and discharging conditions: During charging, the first-stage heat exchanger allocates all its heat for external heating, and the heating load is dynamically adjusted according to the heat user's demand. The heat supplied accounts for 30% to 50% of the total heat of the final stage compression. The second-stage heat exchanger allocates its heat for inlet preheating, and the preheating temperature is automatically adjusted according to the ambient temperature. When the ambient temperature is below 10°C, the inlet preheating is activated to preheat the inlet air temperature to 10 to 15°C. When the ambient temperature is above 15°C, the inlet preheating bypass is activated, and the preheater is taken out of operation. Under discharge conditions, in addition to normal expansion power generation, the hot water in the high-temperature zone of the high-pressure hot water storage tank releases some heat to external heat users through the heating bypass heat exchanger. The heating bypass flow rate does not exceed 20% of the total circulation flow rate of the storage tank.

9. The method according to claim 8, characterized in that, The charging mode also includes: controlling the outlet flow rate of the circulating water pump and the water distribution uniformity of the upper water distributor, so that the heated hot water enters the high-temperature zone of the high-pressure hot water storage tank in a laminar flow state, with a Reynolds number of less than 2000. The temperature distribution inside the high-pressure hot water storage tank is monitored in real time by the temperature sensor array. When the thickness of the thermal stratification transition zone exceeds 30% of the inner cavity height of the high-pressure hot water storage tank, the circulation flow rate is reduced or charging is paused, and charging continues after the stratification is restored. When multiple high-pressure hot water storage tanks are connected in parallel, the number of tanks put into operation is adjusted according to the discharge power demand and the heating load demand. The charging and discharging rate of each tank is controlled by an independent valve to keep the thermal stratification state of each tank balanced.

10. The method according to claim 8, characterized in that, The joint operation mode also includes: dynamically adjusting the flow distribution ratio of each loop in the waste heat diversion heat exchanger through a heating-energy storage priority controller.

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