A heat storage and exchange system with energy storage function for a CAES power station and a collaborative control method thereof

Abstract

The application discloses a CAES power station heat storage and exchange system with energy storage function and a collaborative control method thereof, and belongs to the technical field of compressed air energy storage. The system comprises a high-temperature pressure-bearing water tank, a low-temperature normal-pressure water tank, a high-lift low-temperature pressurizing water pump, a gas-water cooler, a gas-water heater, a hydraulic turbine generator set and a collaborative control system. The application breaks through the technical prejudice that the high-temperature water tank and the low-temperature water tank must be under the same pressure, changes the low-temperature pressure-bearing water tank into a normal-pressure design, pressurizes the normal-pressure working medium by the high-lift low-temperature pressurizing water pump, sends the normal-pressure working medium into the gas-water cooler to absorb the compression heat and store the working medium in the high-temperature pressure-bearing water tank, realizes the 'virtual pumping' energy storage, and releases the heat of the high-temperature working medium by the gas-water heater in the expansion stage, and recovers the pressure energy by the hydraulic turbine generator set to generate electricity. The application realizes the deep coupling of heat storage and pressure energy storage, greatly reduces the investment cost of the storage tank, simultaneously adds the pressure energy storage function, and improves the comprehensive efficiency and economy of the system.

Description

Technical Field

[0001] This invention belongs to the field of compressed air energy storage technology, specifically relating to a CAES power plant heat exchange system with energy storage function and its coordinated control method. Background Technology

[0002] Compressed air energy storage (CAES) is one of the most commercially promising technologies in the field of large-scale, long-duration physical energy storage. CAES recovers the heat of compression through a heat exchange system and uses it for heating the expansion intake air, eliminating the need for fossil fuel combustion. The system efficiency can reach 60%-75%, and it has become the mainstream technology in the industry. As the core subsystem of a CAES power plant, the performance of the heat exchange system directly determines the overall efficiency, investment and operating costs, and safety of the power plant.

[0003] Currently, the industry commonly uses a dual-pressure water tank heat exchange system. The process flow is as follows: During the compression stage, demineralized water in the low-temperature pressurized water tank (operating temperature approximately 60℃) is pressurized by a low-temperature water pump and flows in parallel through a three-stage compressor outlet gas-water cooler to absorb the heat of compression. After heating, it flows into the high-temperature pressurized water tank (operating temperature approximately 210℃) for storage. During the expansion stage, the high-temperature demineralized water in the high-temperature pressurized water tank is pressurized by a high-temperature water pump and flows in parallel through a three-stage turbine inlet gas-water heater to release heat. After cooling, it returns to the low-temperature pressurized water tank. To maintain the demineralized water at 210℃, the high-temperature pressurized water tank uses a constant pressure of approximately 2.4 MPa(g) nitrogen. Because the system is a closed loop, the low-temperature pressurized water tank is forced to use the same constant pressure, and the pump head only overcomes the system resistance of the pipelines and heat exchangers.

[0004] A long-standing technical bias exists in this field: it is widely believed that to ensure the operational stability and leak-free operation of the closed-loop thermal energy storage and exchange system, both high- and low-temperature thermal energy storage tanks must operate at identical constant pressures and maintain overall system connectivity. Any form of pressure decoupling could lead to system pressure runaway, medium vaporization, or operational interruption. This bias has resulted in all commercial CAES power plants worldwide adopting a design where high and low-temperature tanks operate at the same pressure since the application of dual-pressure tank technology, with no attempt yet made to design the low-temperature tanks for atmospheric pressure operation.

[0005] While the aforementioned conventional systems are technically mature, they have inherent drawbacks: the saturated vapor pressure corresponding to the operating temperature of the cryogenic pressurized water tank is only about 0.02 MPa(g), theoretically allowing operation at atmospheric pressure. However, due to system connectivity, it is subjected to a high pressure of 2.4 MPa(g), forcing the cryogenic pressurized water tank to adopt the exact same design pressure, wall thickness, material grade, and manufacturing and inspection standards as the high-temperature pressurized water tank. For a large CAES power plant with a single tank volume of 5000 m³, the steel consumption of the cryogenic pressurized water tank reaches hundreds of tons, and its manufacturing cost is basically equivalent to that of a high-temperature tank of the same volume. This situation can be regarded as an over-design that does not match the process requirements, resulting in 60%–70% unnecessary waste in the investment of cryogenic pressurized water tanks. This has become one of the core bottlenecks restricting the cost reduction of the CAES power plant's heat exchange system, with investment waste reaching tens of millions of yuan for large storage tanks with a capacity of tens of thousands of cubic meters.

[0006] The existing system uses the same nitrogen pressure-maintaining system for both high-temperature and low-temperature pressurized water tanks, providing pressure stability for each. However, the low-temperature tanks themselves do not require high-pressure operation; their need for pressure regulation necessitates a redundant expansion of the nitrogen pressure-maintaining system due to system connectivity constraints. This increases the size of the nitrogen generation system, adds approximately several million yuan to the initial equipment investment, and also increases the system's operational complexity and failure probability. Equipping the low-temperature tanks with an unnecessary nitrogen pressure-maintaining system results in additional parasitic investment and operational losses.

[0007] Existing dual-pressure water tank heat exchange systems only possess a single function of heat energy storage and release, and their energy storage capacity is entirely determined by the temperature difference and mass of the heat exchange medium. The industry has not yet recognized that by rationally reconfiguring the internal pressure distribution of the heat exchange system, additional pressure energy storage and release capacity can be created without affecting the original heat exchange function. This can be transformed into storable and dispatchable energy storage resources through thermodynamic cycle reconstruction, thereby activating the "heat-pressure" synergistic potential of the heat exchange system and significantly improving the system's energy storage density and economic benefits.

[0008] Existing technologies have attempted to achieve pressure isolation by installing pressure-reducing valves between the high- and low-temperature tanks. However, this approach has drawbacks: under pressure differentials exceeding 2.0 MPa, the pressure-reducing valves suffer from severe cavitation and erosion, resulting in a service life of less than one year. Furthermore, the pressure regulation accuracy is low, easily leading to overpressure in the low-temperature tank. Simultaneously, the entire pressure difference is converted into heat energy, wasting resources and reducing the overall system efficiency. Therefore, this approach has not yet been practically applied in engineering projects.

[0009] Currently, in terms of water tank installation height, the industry generally adopts a layout scheme where the two pressure-bearing water tanks of the heat storage and heat exchange system are arranged at the same elevation. Even when there are terrain elevation differences, the water tanks have not yet adopted a differentiated height layout scheme. Summary of the Invention

[0010] The purpose of this invention is to overcome the above-mentioned defects in the prior art and provide a CAES power plant heat exchange system with energy storage function and its coordinated control method. This invention solves the problem that the existing dual-pressure water tank heat exchange system requires the high and low temperature water tanks to be in closed-loop circulation under the same pressure, resulting in excessive redundancy in the design pressure of the low temperature water tank and high production costs.

[0011] On one hand, this invention provides a CAES (Chemical Energy Storage and Heat Exchange) power plant system with energy storage function, including a high-temperature pressurized water tank, a low-temperature atmospheric pressure water tank, a gas-water cooler assembly, a gas-water heater assembly, a high-lift low-temperature booster pump, a hydraulic turbine generator set, and a coordinated control system. The gas-water cooler assembly includes at least one gas-water cooler, the working fluid inlet of which is connected to the outlet of the low-temperature atmospheric pressure water tank, and the working fluid outlet of which is connected to the inlet of the high-temperature pressurized water tank. During the compression stage, the atmospheric pressure heat exchange medium in the low-temperature atmospheric pressure water tank is pressurized by the high-lift low-temperature booster pump and enters the gas-water cooler to absorb heat from the compressed air at the compressor outlet, and is then stored in the high-temperature pressurized water tank after being heated. The gas-water heater assembly includes at least one gas-water heater, the working fluid inlet of which is connected to the outlet of the high-temperature pressurized water tank, and the working fluid outlet of which is connected to the inlet of the low-temperature atmospheric pressure water tank. During the expansion phase, the high-temperature, high-pressure heat exchange medium in the high-temperature pressurized water tank enters the gas-water heater to release heat and heat the turbine inlet air. After releasing heat and cooling, the heat exchange medium is returned to the low-temperature, atmospheric-pressure water tank after generating electricity via the hydraulic turbine generator set. The high-lift, low-temperature booster pump is installed on the pipeline between the outlet of the low-temperature, atmospheric-pressure water tank and the working fluid inlet of the gas-water cooler assembly, used to boost the atmospheric-pressure heat exchange medium in the low-temperature, atmospheric-pressure water tank to the target high-pressure value. The hydraulic turbine generator set is installed on the pipeline between the working fluid outlet of the gas-water heater assembly and the inlet of the low-temperature, atmospheric-pressure water tank, used to recover the pressure energy of the heat exchange medium, which still possesses high-pressure potential energy after releasing heat, into electrical energy. The coordinated control system is used to control the operation of the high-lift, low-temperature booster pump and the hydraulic turbine generator set.

[0012] The core principle of the aforementioned CAES power plant heat exchange system with energy storage function lies in actively cutting off the direct pressure transmission path between the high-temperature and low-temperature heat storage media based on the saturated vapor pressure difference between them, thus constructing two independent thermodynamic "pressure domains": the "high-pressure side" and the "atmospheric pressure side." The high-pressure domain is bound to high-temperature thermal energy, while the atmospheric pressure domain is bound to low-temperature thermal energy, achieving precise matching of energy quality. During the compression (energy storage) stage, a high-lift, low-temperature booster pump pressurizes the atmospheric-pressure low-temperature working fluid to the high-pressure side. This process simulates the "pumping" stage of "pumped hydroelectric energy storage," converting electrical energy into the pressure potential energy of the working fluid, which, along with the absorbed compression heat, is stored in a high-temperature pressurized water tank, achieving "heat-pressure" composite storage. During the expansion (energy release) stage, the sensible heat released by the working fluid in the high-pressure domain is first used to heat the inlet air of the expander. Then, the cooled working fluid, which still has high-pressure potential energy, is expanded and used to generate electricity through a hydraulic turbine unit, realizing the "power generation" link of "pumped storage". At the same time, the pressure energy is recovered into high-quality electrical energy, realizing the timing synchronization and parameter coordination of "heat energy release" and "pressure energy power generation".

[0013] By replacing the cryogenic pressurized water tank with a cryogenic atmospheric pressure water tank design, the design pressure and wall thickness requirements of the cryogenic water tank are significantly reduced, and the investment cost per tank can be reduced by 60%–70%. At the same time, by adding a hydraulic turbine generator set, the pressure energy that was originally wasted through the throttling valve is recovered as electrical energy, realizing the upgrade of the heat storage and exchange system from single thermal energy storage to "thermal energy + pressure energy" composite energy storage, improving the overall efficiency and economic benefits of the system.

[0014] Furthermore, the gas-water cooler assembly includes a first gas-water cooler, a second gas-water cooler, and a third gas-water cooler. The working fluid inlet of the first gas-water cooler, the working fluid inlet of the second gas-water cooler, and the working fluid inlet of the third gas-water cooler are respectively connected in parallel to the outlet of the high-lift low-temperature booster water pump. The working fluid outlet of the first gas-water cooler, the working fluid outlet of the second gas-water cooler, and the working fluid outlet of the third gas-water cooler converge and are connected to the inlet of the high-temperature pressurized water tank.

[0015] In CAES power plants, compressors typically employ multi-stage compression (such as three-stage compression) to improve compression efficiency. Each stage compressor outlet is equipped with a corresponding air-water cooler to recover the heat of compression generated at that stage. The working fluid inlets of the three air-water coolers are connected in parallel to the outlet of a high-lift, low-temperature booster pump, and the working fluid outlets converge and are connected to a high-temperature pressurized water tank. This parallel arrangement allows the working fluid flow rate in each air-water cooler to be distributed according to the heat load of each stage compressor, achieving cascaded recovery of compression heat. The pressurized, atmospheric-pressure working fluid flows in parallel through the air-water coolers at the outlet of the three-stage compressor, absorbing heat from the compressed air at each stage before converging and storing in the high-temperature pressurized water tank.

[0016] Furthermore, the gas-water heater group includes a first gas-water heater, a second gas-water heater, and a third gas-water heater. The working fluid inlet of the first gas-water heater, the working fluid inlet of the second gas-water heater, and the working fluid inlet of the third gas-water heater are respectively connected in parallel to the outlet of the high-temperature pressurized water tank. The working fluid outlet of the first gas-water heater, the working fluid outlet of the second gas-water heater, and the working fluid outlet of the third gas-water heater merge and are connected to the inlet of the hydraulic turbine generator set.

[0017] Corresponding to the compression process, the expansion process typically employs multi-stage expansion (such as three-stage expansion) to improve work efficiency. Each stage of the turbine has a corresponding air-water heater before its inlet to heat the compressed air entering that stage. The working fluid inlets of the three air-water heaters are connected in parallel to the outlet of a high-temperature pressurized water tank. The working fluid outlets converge and are then connected to the hydraulic turbine generator set. The high-temperature, high-pressure heat exchange medium in the high-temperature pressurized water tank flows in parallel through the three-stage turbine inlet air-water heaters, releasing heat to heat the inlet air of each stage of the turbine before converging and entering the hydraulic turbine generator set to recover pressure energy.

[0018] Furthermore, the high-lift cryogenic booster pump is a variable-speed pump, whose head meets the requirements of the constant pressure of the high-temperature pressurized water tank, the resistance drop of the gas-water cooler assembly and pipeline, and the head margin. The inlet of the hydraulic turbine generator set is equipped with a quick-cut-off valve, and the bypass of the hydraulic turbine generator set is equipped with a bypass regulating valve. The high-lift cryogenic booster pump adopts a variable-speed design, and its speed can be adjusted in real time according to the compressor load to achieve dynamic matching between "pump flow rate" and "compression heat power". Its head must meet the requirements of the constant pressure of the high-temperature pressurized water tank, the resistance drop of the gas-water cooler assembly and pipeline, and the head margin, making it a key device for system pressure boosting. The quick-cut-off valve at the inlet of the hydraulic turbine generator set and the bypass regulating valve on the bypass constitute a complete safety protection system. The quick-cut-off valve is used to quickly cut off the flow of the working fluid into the hydraulic turbine in an emergency; the bypass regulating valve is used to achieve stable pressure reduction of the working fluid through throttling during hydraulic turbine failure or maintenance, ensuring continuous system operation.

[0019] Furthermore, the high-temperature pressurized water tank is installed at a higher position than the low-temperature atmospheric pressure water tank, and the head of the high-lift low-temperature booster pump also meets the static pressure requirements of the liquid level difference between the high-temperature pressurized water tank and the low-temperature atmospheric pressure water tank. The high-temperature pressurized water tank is equipped with a nitrogen pressure stabilization system; the low-temperature atmospheric pressure water tank is equipped with a breather valve and a safety valve.

[0020] In engineering sites with terrain elevation differences, high-temperature pressurized water tanks can be positioned at a higher level and low-temperature atmospheric pressure water tanks at a lower level. In this case, the head of the high-lift low-temperature booster pump must not only meet the requirements of the constant pressure of the high-temperature pressurized water tank, the resistance drop of the air-water cooler assembly and pipelines, and the head margin, but also overcome the static pressure difference between the high-temperature pressurized water tank and the low-temperature atmospheric pressure water tank.

[0021] During the compression / energy storage stage, the high-lift, low-temperature booster pump not only pressurizes the working fluid from atmospheric pressure to the high-pressure side but also lifts it from a low to a high level, simultaneously converting electrical energy into the pressure potential energy and gravitational potential energy of the working fluid, thus realizing the complete "pumping" stage of "pumped water storage." During the expansion / energy release stage, the high-temperature, high-pressure working fluid in the high-temperature pressurized water tank, driven by both pressure and gravitational potential energy differences, enters the gas-water heater to release heat. After releasing heat, the working fluid, after generating electricity through the hydraulic turbine generator set, falls back to the low-temperature, atmospheric pressure water tank, where its gravitational potential energy is also converted into electrical energy through the hydraulic turbine.

[0022] The beneficial effects of the above scheme are as follows: By utilizing the terrain elevation difference to achieve a high-level arrangement of the high-temperature pressurized water tank, the system further realizes pumped hydro storage function on the basis of thermal storage and pressure energy storage, enabling the system to simultaneously possess three functions: thermal storage, pressure energy storage, and pumped hydro storage, thereby further improving the system's energy storage density and overall efficiency. The addition of gravitational potential energy increases the energy storage capacity per unit working fluid, improving the system's total energy storage capacity without increasing the amount of working fluid used.

[0023] This invention also provides a collaborative control method for a CAES power plant heat exchange system with energy storage function, comprising the following steps: Step 1: System Status Awareness and Initialization: Confirm that the pressure of the high-temperature pressurized water tank is maintained at the preset pressure, the pressure of the low-temperature atmospheric pressure water tank is maintained at the preset pressure, and all equipment in the system is in normal condition. Step 2: Energy control during the compression and storage stage: Start the high-lift low-temperature booster water pump to pressurize the atmospheric heat exchange medium in the low-temperature atmospheric pressure water tank to the target high pressure value and then send it to the gas-water cooler group to absorb the heat of compression. The heated heat exchange medium is then stored in the high-temperature pressure water tank. Step 3: Energy release control during the expansion and energy release stage: The high-temperature and high-pressure heat exchange medium in the high-temperature pressurized water tank enters the gas-water heater group to release heat and heat the turbine inlet air. After releasing heat and cooling down, the heat exchange medium is depressurized and returned to the low-temperature atmospheric pressure water tank after generating electricity through the hydraulic turbine generator set.

[0024] The above method achieves complete synchronization between the energy storage and release process of pressure energy and the heat exchange process of the CAES power plant, without occupying additional energy storage and release time, and without affecting the normal operation and scheduling of the power plant. Through the complete cycle of "pressurized energy storage - hydraulic turbine power generation", the heat exchange system has been upgraded from single thermal energy storage to "thermal energy + pressure energy" composite energy storage.

[0025] Furthermore, in step two, the real-time output of the compressor serves as the feedforward signal, while the rate of change in the inlet temperature or liquid level of the high-temperature pressurized water tank acts as the feedback signal. This closed-loop adjustment of the high-lift, low-temperature booster pump's speed ensures that the electrical power consumed by the pump matches the compression heat power generated by the compressor in real time. When the liquid level or pressure in the high-temperature pressurized water tank reaches its upper limit, the charging process automatically stops. This precise matching of pump power consumption and compressor heat power output avoids insufficient heat recovery due to insufficient flow and energy waste due to excessive flow. The automatic charging stop function ensures system safety and prevents overpressure or overflow in the high-temperature pressurized water tank.

[0026] Furthermore, in step three, the real-time air intake demand of the turbine is used as the feedforward signal, and the outlet working fluid pressure or temperature of the gas-water heater group is used as the feedback signal to dynamically adjust the guide vane opening of the hydraulic turbine generator group. While ensuring the stability of the outlet working fluid pressure of the gas-water heater group, the speed of the hydraulic turbine generator group is controlled in the optimal efficiency range. When the liquid level of the high-temperature pressurized water tank reaches the lower limit, the outlet valve is closed and the hydraulic turbine generator group stops generating electricity.

[0027] Furthermore, the collaborative control method also includes multimodal safety redundancy control steps: when the hydraulic turbine generator set fails, the quick-cut-off valve at the inlet of the hydraulic turbine generator set is closed, and the bypass regulating valve is opened to achieve throttling and pressure reduction. The working fluid is stably depressurized through throttling to ensure continuous system operation and avoid system shutdown due to hydraulic turbine failure; when the pressure of the low-temperature atmospheric pressure water tank exceeds the safety preset value, the safety valve is automatically opened to release pressure and ensure that the tank does not overpressure; when the pressure of the high-temperature pressurized water tank exceeds the safety preset value, the nitrogen pressure relief valve is interlocked to open to release the pressure inside the tank and prevent overpressure accidents.

[0028] Compared with existing dual-pressurized water tank heat exchange systems, the present invention has the following advantages: First, converting cryogenic water tanks from high-pressure vessels to atmospheric-pressure vessels can reduce wall thickness by approximately 70%, lowering single-tank investment costs by 60%–70%. This significantly saves on steel, welding, and testing costs, while also reducing the load and cost of the corresponding civil engineering foundations. Completely eliminating the nitrogen pressure-regulating system of the cryogenic atmospheric-pressure water tank saves on equipment investment and reduces annual maintenance costs, resulting in significant economic benefits.

[0029] Second, the hydraulic turbine generator set enables precise and continuous pressure reduction from high-pressure water to atmospheric water, solving the overpressure hazard in the low-temperature atmospheric pressure tank caused by pressure transmission from the high-temperature tank; the mature and reliable nitrogen pressure stabilization system of the high-temperature pressurized water tank is fully retained, and the system's operational stability is consistent with the original dual-pressurized water tank system; the hydraulic turbine also has an overpressure protection function, further improving system safety.

[0030] Third, the time-series synchronous coupling of thermal energy, pressure energy, and gravitational potential energy is achieved. The energy storage and release processes of pressure energy and gravitational potential energy are completely synchronized with the heat storage and exchange processes of the CAES power plant, without occupying additional energy storage and release time, and without affecting the normal operation and scheduling of the power plant, thus realizing the deep coupling and integration of multiple energy storage forms.

[0031] IV. Outstanding Engineering Advantages and Compatibility. The system of this invention eliminates the safety hazards of cryogenic side pressure vessels, reduces the workload of a high-pressure special equipment and its routine maintenance, and utilizes a hydraulic turbine to achieve stable pressure reduction, avoiding the wear and tear caused by erosion and cavitation under high pressure differentials in traditional pressure reducing valves. This extends the service life of critical valves and improves the long-term reliability of the system. This system fully inherits the operating characteristics and control logic of existing mature systems, requiring no retraining for operators; all equipment is domestically produced, with a mature and stable supply chain; it can be directly applied to newly built CAES power plants, and can also be used for low-cost retrofitting of existing dual-pressure tank systems.

[0032] V. Promoting the upgrade of CAES power plant heat storage and exchange systems from "single heat storage" to "composite energy storage". This invention is the first to achieve "thermal-pressure decoupling" of a CAES power plant heat storage and exchange system in engineering practice, and constructs an embedded "virtual pumped hydro storage" cycle. This not only reduces investment and improves efficiency, but more importantly, it pioneers a new form of energy storage system, providing a new technical path and theoretical basis for the deep coupling of next-generation compressed air energy storage systems with pumped hydro storage, batteries, and other energy storage forms. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the CAES power plant's heat storage and exchange system when the high-temperature pressurized water tank and the low-temperature atmospheric pressure water tank are at the same height.

[0034] Figure 2 A schematic diagram of the CAES power plant heat storage and exchange system when the high-temperature pressurized water tank is installed at a higher position than the low-temperature atmospheric pressure water tank.

[0035] Among them, 1. High-temperature pressurized water tank; 2. Low-temperature atmospheric pressure water tank; 3. Gas-water cooler group; 31. First gas-water cooler; 32. Second gas-water cooler; 33. Third gas-water cooler; 4. Gas-water heater group; 41. First gas-water heater; 42. Second gas-water heater; 43. Third gas-water heater; 5. High-lift low-temperature booster water pump; 6. Hydraulic turbine generator set; 7. Bypass regulating valve. Detailed Implementation

[0036] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0037] Example 1, as Figure 1 As shown, this embodiment provides a CAES power plant heat exchange system with energy storage function, including a high-temperature pressurized water tank 1, a low-temperature atmospheric pressure water tank 2, a gas-water cooler group 3, a gas-water heater group 4, a high-lift low-temperature booster water pump 5, a hydraulic turbine generator set 6, and a bypass regulating valve 7. The high-temperature pressurized water tank 1 and the low-temperature atmospheric pressure water tank 2 are arranged at the same elevation.

[0038] High-temperature pressurized water tank 1 is used to store high-temperature and high-pressure heat exchange medium (demineralized water), with an operating temperature of 210℃ and an operating pressure of 2.2 MPa(g). High-temperature pressurized water tank 1 is equipped with a nitrogen pressure stabilization system to maintain the operating pressure of high-temperature pressurized water tank 1 at 2.2 MPa(g) ± 0.1 MPa(g). Low-temperature atmospheric pressure water tank 2 is used to store low-temperature atmospheric pressure heat exchange medium (demineralized water), with an operating temperature of 60℃ and an operating pressure of 0.08 MPa(g)–0.09 MPa(g). Low-temperature atmospheric pressure water tank 2 is equipped with a breather valve and a safety valve on its top, both open to the atmosphere. The breather valve opens at a pressure of 0.08 MPa(g), and the safety valve opens at a pressure of 0.09 MPa(g), ensuring that the tank does not overpressure.

[0039] The air-water cooler assembly 3 includes a first air-water cooler 31, a second air-water cooler 32, and a third air-water cooler 33. The working fluid inlets of the first air-water cooler 31, the second air-water cooler 32, and the third air-water cooler 33 are connected in parallel to the outlet of the high-lift, low-temperature booster pump 5. The working fluid outlets of the first air-water cooler 31, the second air-water cooler 32, and the third air-water cooler 33 converge and connect to the inlet of the high-temperature pressurized water tank 1.

[0040] The gas-water heater group 4 includes a first gas-water heater 41, a second gas-water heater 42, and a third gas-water heater 43. The working fluid inlets of the first gas-water heater 41, the second gas-water heater 42, and the third gas-water heater 43 are connected in parallel to the outlet of the high-temperature pressurized water tank 1. The working fluid outlets of the first gas-water heater 41, the second gas-water heater 42, and the third gas-water heater 43 merge and are connected to the inlet of the hydraulic turbine generator set 6.

[0041] The high-lift cryogenic booster pump 5 is installed on the pipeline between the outlet of the cryogenic atmospheric pressure water tank 2 and the working fluid inlet of the gas-water cooler group 3. The high-lift cryogenic booster pump 5 is a variable-speed pump, and its head meets the requirements of the constant pressure of the high-temperature pressurized water tank 1 (2.4 MPa(g)), the resistance drop of the gas-water cooler group 3 and the pipeline, and the head margin. The high-lift cryogenic booster pump 5 is a key device for system pressure boosting; its speed is adjusted in real time according to the compressor load, achieving dynamic matching between the "pump flow rate" and the "compression heat power".

[0042] The hydraulic turbine generator set 6 is installed on the pipeline between the working fluid outlet of the gas-water heater group 4 and the inlet of the cryogenic atmospheric pressure water tank 2, completely replacing the throttling and pressure reducing valve group in the traditional system. The design operating inlet pressure of the hydraulic turbine generator set 6 is the combined pressure of the outlet of the gas-water heater group 4 (approximately 2.0 MPa(g)), and the outlet leads to the cryogenic atmospheric pressure water tank 2. The design flow rate matches the maximum circulating flow rate of the system to efficiently recover pressure difference for power generation. The inlet of the hydraulic turbine generator set 6 is equipped with a quick-shut-off valve, and the bypass of the hydraulic turbine generator set 6 is equipped with a bypass regulating valve 7.

[0043] The system in this embodiment is also equipped with a collaborative control system for controlling the operation of the high-lift cryogenic booster water pump 5 and the hydraulic turbine generator set 6. The collaborative control system receives compressor power, turbine power, and pressure and temperature signals from the high-temperature pressurized water tank 1 and the cryogenic atmospheric pressure water tank 2, calculates them in real time, and sends commands to the high-lift cryogenic booster water pump 5 and the hydraulic turbine generator set 6, ensuring the safe, normal, and stable operation of the collaborative control system.

[0044] The system working principle of this embodiment is as follows: Compression / Storage Stage: The high-lift, low-temperature booster pump 5 draws in atmospheric-pressure demineralized water from the low-temperature atmospheric-pressure water tank 2, increasing the working fluid pressure from 0.1 MPa to over 2.4 MPa (g), enabling it to enter the high-temperature pressurized water tank 1. The pressurized demineralized water flows in parallel through the first air-water cooler 31, the second air-water cooler 32, and the third air-water cooler 33, absorbing heat from the compressed air at the outlets of the first-stage, second-stage, and third-stage compressors, respectively, thus achieving heat storage. The demineralized water, after absorbing heat and increasing its temperature, is collected and stored in the high-temperature pressurized water tank 1. At this point, the water is in a high-temperature, high-pressure state (approximately 210°C, 2.2 MPa (g)), simultaneously storing thermal energy and pressure potential energy, achieving "heat-pressure" composite storage. During this process, the high-lift, low-temperature booster pump 5 consumes electrical energy, converting it into the pressure potential energy of the working fluid, simulating the "pumping" stage of "pumped water storage".

[0045] Expansion / Energy Release Stage: Utilizing the pressure difference between the high-temperature pressurized water tank 1 and the low-temperature atmospheric pressure water tank 2, the high-temperature, high-pressure demineralized water working fluid in the high-temperature pressurized water tank 1 is sent to the first air-water heater 41, the second air-water heater 42, and the third air-water heater 43, releasing heat to heat the air about to enter each stage of the turbine, completing the sensible heat release and cooling process. After the heat release and cooling, the demineralized water working fluid still maintains a high pressure of approximately 2.0 MPa (g). Before flowing back to the low-temperature atmospheric pressure water tank 2 through the main pipeline, it is not throttled but entirely introduced into the hydraulic turbine generator set 6. The high-pressure demineralized water drives the hydraulic turbine to rotate, driving the generator to generate electrical energy, recovering pressure potential energy as electrical energy. After the hydraulic turbine performs work and reduces pressure, the demineralized water pressure drops to near atmospheric pressure and then safely returns to the low-temperature atmospheric pressure water tank 2, completing the cycle.

[0046] The collaborative control method in this embodiment is as follows: Step 1: System Status Awareness and Initialization: Confirm that the pressure of high-temperature pressurized water tank 1 is maintained at 2.2±0.1MPa(g), the pressure of low-temperature atmospheric pressure water tank 2 is maintained at 0.08–0.09MPa(g), and all equipment, valves and instruments in the system are in normal condition.

[0047] Step 2, Energy Control During the Compression and Storage Stage: Start the high-lift, low-temperature booster pump 5 to pressurize the demineralized water in the low-temperature atmospheric pressure water tank 2 to the target high pressure value of 2.4 MPa(g). Using the real-time output of the compressor as the feedforward signal and the inlet temperature or liquid level change rate of the high-temperature pressurized water tank 1 as the feedback signal, the speed of the high-lift, low-temperature booster pump 5 is adjusted in a closed loop to ensure that the electrical power consumed by the high-lift, low-temperature booster pump 5 matches the compression heat power generated by the compressor in real time, achieving synchronous charging and efficient storage of thermal and pressure energy. When the liquid level or pressure in the high-temperature pressurized water tank 1 reaches the upper limit, the charging process automatically stops.

[0048] Step 3: Energy Release Control During the Expansion and Release Stage: Open the outlet valve of the high-temperature pressurized water tank 1. Utilize the static pressure difference between the high-temperature pressurized water tank 1 and the low-temperature atmospheric pressure water tank 2 to pressurize the high-temperature demineralized water into the first gas-water heater 41, the second gas-water heater 42, and the third gas-water heater 43. Using the real-time turbine intake demand as the feedforward signal and the outlet working fluid pressure or temperature of the gas-water heater group 4 as the feedback signal, dynamically adjust the guide vane opening of the hydraulic turbine generator set 6. While ensuring a stable outlet working fluid pressure of the gas-water heater group 4 (e.g., P=2.0±0.1MPa) to ensure a smooth heat release process, control the speed of the hydraulic turbine generator set 6 within the optimal efficiency range to maximize the "virtual power generation" power. When the liquid level in the high-temperature pressurized water tank 1 reaches the lower limit, close the outlet valve, and the hydraulic turbine generator set 6 stops generating electricity.

[0049] Step 4, Multimodal Safety Redundancy Control: When the hydraulic turbine generator set 6 fails, the quick-cut-off valve at the inlet of the hydraulic turbine generator set 6 is closed, and the bypass regulating valve 7 is opened at the same time to achieve stable pressure reduction through throttling; when the pressure of the low-temperature atmospheric pressure water tank 2 exceeds 0.09MPa(g), the safety valve is automatically opened to release pressure; when the pressure of the high-temperature pressure water tank 1 exceeds 2.5MPa(g), the nitrogen pressure relief valve is interlocked to open.

[0050] Example 2, as Figure 2 As shown, this embodiment provides a CAES power plant heat exchange system with energy storage function. The difference between this system and Embodiment 1 is that the high-temperature pressurized water tank 1 is installed at a higher position than the low-temperature atmospheric pressure water tank 2. This embodiment fully utilizes the terrain elevation differences at the engineering site, arranging the high-temperature pressurized water tank 1 at a higher position and the low-temperature atmospheric pressure water tank 2 at a lower position. In addition to achieving heat storage and pressure energy storage functions, it further realizes pumped storage energy storage.

[0051] In this embodiment, the high-temperature pressurized water tank 1 is positioned at a high level, while the low-temperature atmospheric pressure water tank 2 is positioned at a low level. The head of the high-lift low-temperature booster pump 5 must not only meet the requirements of the constant pressure of the high-temperature pressurized water tank 1, the resistance drop of the air-water cooler assembly 3 and the pipeline, and the head margin, but also the static pressure requirement of the liquid level difference between the high-temperature pressurized water tank 1 and the low-temperature atmospheric pressure water tank 2. The pump outlet pressure is also correspondingly increased by the static pressure of the liquid level difference.

[0052] In this embodiment, the air-water cooler group 3 includes a first air-water cooler 31, a second air-water cooler 32, and a third air-water cooler 33. The working fluid inlets of the first air-water cooler 31, the second air-water cooler 32, and the third air-water cooler 33 are connected in parallel to the outlet of the high-lift, low-temperature booster pump 5. The working fluid outlets of the first air-water cooler 31, the second air-water cooler 32, and the third air-water cooler 33 converge and connect to the inlet of the high-level high-temperature pressurized water tank 1. The air connection method of each air-water cooler is the same as in Embodiment 1.

[0053] The gas-water heater group 4 includes a first gas-water heater 41, a second gas-water heater 42, and a third gas-water heater 43. The working fluid inlets of the first gas-water heater 41, the second gas-water heater 42, and the third gas-water heater 43 are connected in parallel to the outlet of the high-temperature pressurized water tank 1. The working fluid outlets of the first gas-water heater 41, the second gas-water heater 42, and the third gas-water heater 43 converge and connect to the inlet of the hydraulic turbine generator set 6. The air connection method for each gas-water heater is the same as in Embodiment 1.

[0054] A high-lift, low-temperature booster water pump 5 is installed on the pipeline between the outlet of the low-temperature atmospheric pressure water tank 2 and the working fluid inlet of the gas-water cooler group 3, and is a variable-speed water pump. A hydraulic turbine generator set 6 is installed on the pipeline between the working fluid outlet of the gas-water heater group 4 and the inlet of the low-temperature atmospheric pressure water tank 2. The inlet of the hydraulic turbine generator set 6 is equipped with a quick-shut-off valve, and the bypass of the hydraulic turbine generator set 6 is equipped with a bypass regulating valve 7.

[0055] The system working principle of this embodiment is as follows: Compression / Energy Storage Stage: The high-lift cryogenic booster pump 5 draws in atmospheric demineralized water from the low-lying cryogenic atmospheric pressure water tank 2, raising the working fluid pressure from 0.1 MPa to the target high pressure value. Besides overcoming the constant pressure (2.4 MPa(g)) of the high-temperature pressurized water tank 1 and pipeline resistance, the high-lift cryogenic booster pump 5 also needs to overcome the increased static pressure due to the higher position of the high-temperature pressurized water tank 1. During this process, the high-lift cryogenic booster pump 5 not only increases the pressure energy of the water but also raises the water from a low to a high level, realizing the "pumping" stage of "pumping for energy storage," simultaneously converting electrical energy into the pressure potential energy and gravitational potential energy of the working fluid. The pressurized demineralized water working fluid flows in parallel through the first gas-water cooler 31, the second gas-water cooler 32, and the third gas-water cooler 33, respectively absorbing heat from the compressed air at the outlet of each stage compressor, thus achieving the heat storage process. The demineralized water working fluid, after absorbing heat and heating up, is collected and stored in a high-temperature pressurized water tank 1 located at a high level.

[0056] Expansion / Energy Release Stage: The high-temperature, high-pressure demineralized water working fluid in the high-temperature pressurized water tank 1, driven by both pressure and gravitational potential energy differences, enters the first air-water heater 41, the second air-water heater 42, and the third air-water heater 43, releasing heat to heat the air about to enter each stage of the turbine, completing the sensible heat release and cooling process. After the heat release and cooling, the demineralized water working fluid still maintains a high pressure of approximately 2.0 MPa(g). Before flowing back to the low-temperature atmospheric pressure water tank 2 through the main pipeline, it is not throttled but entirely introduced into the hydraulic turbine generator set 6. The high-pressure demineralized water drives the hydraulic turbine to rotate, driving the generator to generate electricity. Simultaneously, the working fluid falls from a high position to a low position, and its gravitational potential energy is also converted into electrical energy through the hydraulic turbine, realizing the "power generation" stage of "pumped water storage". After the hydraulic turbine performs work to reduce pressure, the demineralized water pressure drops to near atmospheric pressure and returns to the low-temperature atmospheric pressure water tank 2, completing the cycle.

[0057] Based on Example 1, this embodiment further utilizes the terrain elevation difference to realize the storage and release of gravitational potential energy, enabling the system to simultaneously possess three functions: thermal storage, pressure energy storage, and pumped hydro storage, thereby further improving the system's energy storage density and overall efficiency.

[0058] The collaborative control method in this embodiment is basically the same as that in Embodiment 1, except that: in the energy charging control of the compression and energy storage stage in step two, the target high pressure value of the high-lift low-temperature booster pump 5 needs to be increased accordingly by the static pressure value of the liquid level difference between the high-temperature pressurized water tank 1 and the low-temperature atmospheric pressure water tank 2; in the energy release control of the expansion and energy release stage in step three, the working fluid at the outlet of the high-temperature pressurized water tank 1 enters the gas-water heater group 4 under the combined drive of the pressure difference and the gravitational potential energy difference. The remaining control steps are completely consistent with those in Embodiment 1.

[0059] In both of the above embodiments, the system is equipped with comprehensive security protection measures: Overpressure protection: The top of the low-temperature atmospheric pressure water tank 2 is equipped with a breather valve and a safety valve. The breather valve opens at a pressure of 0.08 MPa (g), and the safety valve opens at a pressure of 0.09 MPa (g), ensuring that the tank will not be overpressured.

[0060] Hydraulic turbine fault protection: A quick-cut-off valve and a bypass regulating valve 7 are installed at the inlet of the hydraulic turbine generator set 6. When the hydraulic turbine generator set 6 fails, the quick-cut-off valve closes and the bypass regulating valve 7 automatically opens, reducing pressure through throttling to ensure continuous system operation.

[0061] Liquid level interlock protection: A high and low liquid level interlock is set. When the liquid level of the high-temperature pressurized water tank 1 is too high, the high-lift low-temperature booster water pump 5 will be stopped by the interlock; when the liquid level of the low-temperature atmospheric pressure water tank 2 is too low, the high-lift low-temperature booster water pump 5 will be stopped by the interlock.

[0062] Pressure interlock protection: When the pressure of high-temperature pressurized water tank 1 exceeds 2.5MPa(g), the nitrogen pressure relief valve is opened by interlock; when the pressure of high-temperature pressurized water tank 1 is lower than 2.3MPa(g), the nitrogen replenishment regulating valve is opened by interlock.

[0063] Economic Analysis: Based on a project scale of 350MW / 2100MWh, the economic analysis of this invention is as follows: New investment: Equipment cost (1 hydraulic turbine generator set, 2 cryogenic booster water pumps, regulating valve set, etc.) approximately RMB 4 million; installation cost approximately RMB 1 million; construction cost approximately RMB 600,000; material cost approximately RMB 300,000; total approximately RMB 5.9 million.

[0064] Investment savings: Replacing the cryogenic pressurized water tanks with cryogenic atmospheric pressure water tanks, each with a water volume of approximately 5000 m³, and requiring three tanks, reduces the tank wall thickness from 56 mm to 18 mm, decreasing steel consumption from 722 tons to 232 tons. The three cryogenic atmospheric pressure water tanks will save a total of approximately 22.05 million yuan in investment; the reduced capacity of the nitrogen constant pressure system will save approximately 4 million yuan in investment; and the reduced weight of the cryogenic atmospheric pressure water tanks will reduce equipment foundation construction costs by approximately 800,000 yuan; totaling approximately 26.85 million yuan.

[0065] Annual operating revenue: Annual electricity consumption: 1000kW (low-temperature water booster pump power) × 8h (compression time) × 330 (330 days of operation per year) × 0.3 yuan (off-peak electricity price) = 790,000 yuan; Annual electricity sales revenue: 875kW (hydraulic turbine generator set power) × 6h (expansion time) × 330 (330 days of operation per year) × 0.6 yuan (peak electricity price) = 1,040,000 yuan; Electricity price arbitrage: 250,000 yuan.

[0066] The above economic analysis shows that, after implementation, this invention saves 20.95 million yuan more in investment compared to the original system, and benefits can be generated immediately upon implementation. Furthermore, the accompanying pressure energy storage system, utilizing electricity price differences, generates 250,000 yuan annually, resulting in a total revenue of approximately 10 million yuan over the power station's entire lifecycle, demonstrating significant economic value.

Claims

1. A CAES power plant heat exchange system with energy storage function, characterized in that, High-temperature pressurized water tank (1), low-temperature atmospheric pressure water tank (2), gas-water cooler group (3), gas-water heater group (4), high-lift low-temperature booster water pump (5), hydraulic turbine generator set (6) and coordinated control system. The gas-water cooler group (3) includes at least one gas-water cooler, the working fluid inlet of the gas-water cooler is connected to the outlet of the low temperature atmospheric pressure water tank (2), and the working fluid outlet of the gas-water cooler is connected to the inlet of the high temperature pressure water tank (1). The gas-water heater assembly includes at least one gas-water heater, the working fluid inlet of the gas-water heater is connected to the outlet of the high-temperature pressurized water tank (1), and the working fluid outlet of the gas-water heater is connected to the inlet of the low-temperature atmospheric pressure water tank (2). The high-lift low-temperature booster pump (5) is installed on the pipeline between the outlet of the low-temperature atmospheric pressure water tank (2) and the working fluid inlet of the gas-water cooler group (3); The hydraulic turbine generator set (6) is installed on the pipeline between the working fluid outlet of the gas-water heater set (4) and the inlet of the low-temperature atmospheric pressure water tank (2); The coordinated control system is used to control the operation of the high-lift cryogenic booster water pump (5) and the hydraulic turbine generator set (6).

2. The CAES power plant heat exchange system with energy storage function according to claim 1, characterized in that, The gas-water cooler group (3) includes a first gas-water cooler (31), a second gas-water cooler (32), and a third gas-water cooler (33). The working fluid inlet of the first gas-water cooler (31), the working fluid inlet of the second gas-water cooler (32), and the working fluid inlet of the third gas-water cooler (33) are connected in parallel with the outlet of the high-lift low-temperature booster pump (5). The working fluid outlet of the first gas-water cooler (31), the working fluid outlet of the second gas-water cooler (32), and the working fluid outlet of the third gas-water cooler (33) are connected to the inlet of the high-temperature pressurized water tank (1) after they merge.

3. The CAES power plant heat exchange system with energy storage function according to claim 1, characterized in that, The gas-water heater group (4) includes a first gas-water heater (41), a second gas-water heater (42), and a third gas-water heater (43). The working fluid inlet of the first gas-water heater (41), the working fluid inlet of the second gas-water heater (42), and the working fluid inlet of the third gas-water heater (43) are connected in parallel to the outlet of the high-temperature pressurized water tank (1). The working fluid outlet of the first gas-water heater (41), the working fluid outlet of the second gas-water heater (42), and the working fluid outlet of the third gas-water heater (43) are connected to the inlet of the hydraulic turbine generator set (6) after they merge.

4. The CAES power plant heat exchange system with energy storage function according to claim 1, characterized in that, The high-lift low-temperature booster pump (5) is a variable speed pump, and its lift meets the requirements of the constant pressure of the high-temperature pressurized water tank (1), the resistance drop of the gas-water cooler group (3) and the pipeline, and the lift margin. The inlet of the hydraulic turbine generator set (6) is equipped with a quick shut-off valve, and the bypass of the hydraulic turbine generator set (6) is equipped with a bypass regulating valve (7).

5. The CAES power plant heat exchange system with energy storage function according to claim 1, characterized in that, The high-temperature pressurized water tank (1) is installed at a higher position than the low-temperature atmospheric pressure water tank (2). The head of the high-lift low-temperature booster pump (5) also meets the static pressure requirements of the liquid level difference between the high-temperature pressurized water tank (1) and the low-temperature atmospheric pressure water tank (2). The high-temperature pressurized water tank (1) is equipped with a nitrogen constant pressure system. The low-temperature atmospheric pressure water tank (2) is equipped with a breather valve and a safety valve.

6. A collaborative control method for a CAES power plant heat exchange system with energy storage function, applied to the CAES power plant heat exchange system with energy storage function as described in any one of claims 1 to 5, characterized in that, Includes the following steps: Step 1: System status perception and initialization: Confirm that the pressure of the high temperature pressurized water tank (1) is maintained at the preset pressure, the pressure of the low temperature atmospheric pressure water tank (2) is maintained at the preset pressure, and all equipment in the system is in normal condition; Step 2: Energy control during the compression and storage stage: Start the high-lift low-temperature booster water pump (5) to pressurize the atmospheric heat exchange medium in the low-temperature atmospheric pressure water tank (2) to the target high pressure value and then send it into the gas-water cooler group (3) to absorb the heat of compression. The heated heat exchange medium is then stored in the high-temperature pressure water tank (1). Step 3: Energy release control during the expansion and energy release stage: The high-temperature and high-pressure heat exchange medium in the high-temperature pressurized water tank (1) enters the gas-water heater group (4) to release heat and heat the turbine inlet air. After the heat exchange medium is cooled down, it performs power generation through the hydraulic turbine generator group (6) and then returns to the low-temperature atmospheric pressure water tank (2) after depressurization.

7. The collaborative control method for a CAES power plant heat exchange system with energy storage function according to claim 6, characterized in that, In step two, the real-time output of the compressor is used as the feedforward signal, and the inlet temperature or liquid level change rate of the high-temperature pressurized water tank (1) is used as the feedback signal to adjust the speed of the high-lift low-temperature booster water pump (5) in a closed loop so that the electrical power consumed by the high-lift low-temperature booster water pump (5) matches the compression heat power generated by the compressor in real time; when the liquid level or pressure of the high-temperature pressurized water tank (1) reaches the upper limit, the charging process is automatically stopped.

8. The collaborative control method for a CAES power plant heat exchange system with energy storage function according to claim 6, characterized in that, In step three, the real-time intake demand of the turbine is used as the feedforward signal, and the working fluid pressure or temperature at the outlet of the gas-water heater group (4) is used as the feedback signal to dynamically adjust the guide vane opening of the hydraulic turbine generator group (6). While ensuring the stability of the working fluid pressure at the outlet of the gas-water heater group (4), the speed of the hydraulic turbine generator group (6) is controlled in the optimal efficiency range. When the liquid level of the high-temperature pressurized water tank (1) reaches the lower limit, the outlet valve is closed and the hydraulic turbine generator group (6) stops generating electricity.

9. The coordinated control method for a CAES power plant heat exchange system with energy storage function according to claim 6, characterized in that, It also includes multi-modal safety redundancy control steps: when the hydraulic turbine generator set (6) fails, the quick shut-off valve at the inlet of the hydraulic turbine generator set (6) is closed, and the bypass regulating valve (7) is opened at the same time to achieve throttling and pressure reduction; when the pressure of the low temperature atmospheric pressure water tank (2) exceeds the safety preset value, the safety valve is automatically opened to release pressure; when the pressure of the high temperature pressure water tank (1) exceeds the safety preset value, the nitrogen pressure relief valve is interlocked to open.

Images