Photovoltaic-driven compressed air energy storage system with multi-stage compression and segmented heat recovery

Abstract

This invention proposes a photovoltaic-driven compressed air energy storage system with multi-stage compression and segmented heat recovery. The system includes: photovoltaic modules, a multi-stage compressor unit, a thermal storage heat exchanger, a high-temperature thermal storage tank, a low-temperature thermal storage tank, a regenerative heat exchanger, an expander, and an ORC unit. The photovoltaic modules supply power to the multi-stage compressor unit, which compresses the gas and stores it in the gas storage tank. Part of the heat generated is stored in the high-temperature contact tank and the low-temperature thermal storage tank through two thermal storage heat exchangers. The gas storage tank then feeds the high-pressure gas into the expander for expansion and work, driving a generator to produce electricity. Part of the waste heat from the expander's exhaust gas is fed into the ORC unit for secondary power generation, realizing waste heat utilization. This invention achieves efficient utilization and long-term energy storage of photovoltaic energy, significantly improving energy efficiency and operational safety, and solving the problems of low efficiency, large heat loss, and insufficient regulation capacity in traditional compressed air energy storage systems.

Description

Technical Field

[0001] This invention relates to the fields of photovoltaic power generation and compressed air energy storage technology, and in particular to a photovoltaic-driven compressed air energy storage system with multi-stage compression and segmented heat recovery. Background Technology

[0002] Photovoltaic power generation has advantages such as being clean, renewable, and environmentally friendly. However, its output power fluctuates with sunlight intensity, exhibiting significant intermittency and randomness, making it difficult to directly match grid demand. Therefore, how to efficiently store and utilize photovoltaic energy has become a crucial issue restricting the absorption and utilization of new energy sources.

[0003] Compressed air energy storage (CAES), as a large-scale energy storage technology, utilizes electricity to drive a compressor to compress air and store it in a high-pressure storage tank. When needed, the air is released to drive an expander to generate electricity. It boasts advantages such as large storage capacity, long lifespan, and fast response speed. Existing CAES systems mostly use grid power as the compressor's driving power source. In research combining it with photovoltaic power generation, the main approach is to invert the photovoltaic power and connect it to the grid, which then supplies power to the compressor. This results in low system coupling and problems such as a long energy conversion chain and significant losses. Furthermore, traditional CAES systems generate a large amount of compression heat during compression. If this heat is not recovered, it will lead to reduced energy utilization efficiency. Some existing technologies attempt to store waste heat using a single heat storage tank. However, due to the wide temperature range and significant quality differences of compression heat, a single heat storage tank cannot efficiently utilize heat energy at different temperatures, often resulting in the waste of some low-temperature waste heat, thus limiting the overall energy efficiency improvement of the system. Summary of the Invention

[0004] The purpose of this invention is to at least partially solve one of the technical problems in related technologies. To this end, embodiments of this invention provide a photovoltaic-driven compressed air energy storage system with multi-stage compression and segmented heat recovery. This system can effectively utilize photovoltaic energy, achieve efficient absorption of photovoltaic power generation, improve energy utilization efficiency, and fully utilize the waste heat generated during compression to achieve multi-temperature zone heat storage and segmented utilization.

[0005] This invention proposes a photovoltaic-driven compressed air energy storage system with multi-stage compression and segmented heat recovery, comprising: photovoltaic modules, multi-stage compressor units, a primary heat storage heat exchanger, a secondary heat storage heat exchanger, a high-temperature heat storage tank, a low-temperature heat storage tank, a primary regenerative heat exchanger, a secondary regenerative heat exchanger, a primary expander, and a secondary expander.

[0006] The photovoltaic module is electrically connected to the multi-stage compressor unit, which supplies power to the multi-stage compressor unit. The multi-stage compressor unit includes a primary compressor, a secondary compressor, and a tertiary compressor. Air is introduced into the air inlet of the primary compressor, and the exhaust port of the primary compressor is connected to the air inlet of the secondary compressor. The exhaust port of the secondary compressor is connected to the air inlet of the tertiary compressor, and the exhaust port of the tertiary compressor is connected to the air storage tank.

[0007] The primary heat regenerator has a tube-side inlet and a tube-side outlet, as well as a shell-side inlet and a shell-side outlet. The primary heat regenerator is connected to the connecting pipeline between the tube-side outlet of the primary compressor and the tube-side inlet of the secondary compressor. The secondary heat regenerator has a tube-side inlet and a tube-side outlet, as well as a shell-side inlet and a shell-side outlet. The secondary heat regenerator is connected to the connecting pipeline between the tube-side outlet of the secondary compressor and the tube-side inlet of the tertiary compressor.

[0008] The high-temperature heat storage tank has an air inlet and an air outlet, and the low-temperature heat storage tank has an air inlet and an air outlet. The shell-side air outlet of the first-stage heat storage heat exchanger is connected to the air inlet of the high-temperature heat storage tank, and the air outlet of the high-temperature heat storage tank is connected to the air inlet of the low-temperature heat storage tank. The air outlet of the low-temperature heat storage tank is connected to the shell-side air inlet of the first-stage heat storage heat exchanger and the shell-side air inlet of the second-stage heat storage heat exchanger, respectively. The air inlet of the high-temperature heat storage tank is connected to the shell-side air outlet of the first-stage heat storage heat exchanger and the shell-side air outlet of the second-stage heat storage heat exchanger, respectively.

[0009] The first-stage regenerative heat exchanger has a tube-side air inlet and a tube-side air outlet, as well as a shell-side air inlet and a shell-side air outlet. The second-stage regenerative heat exchanger also has a tube-side air inlet and a tube-side air outlet, as well as a shell-side air inlet and a shell-side air outlet. The air outlet of the high-temperature heat storage tank is connected to the tube-side air inlet of the first-stage regenerative heat exchanger and the tube-side air inlet of the second-stage regenerative heat exchanger, respectively. The air inlet of the low-temperature heat storage tank is connected to the tube-side air outlet of the first-stage regenerative heat exchanger and the tube-side air outlet of the second-stage regenerative heat exchanger, respectively. The air outlet of the gas storage tank is connected to the shell-side air inlet of the first-stage regenerative heat exchanger.

[0010] The shell-side exhaust port of the first-stage regenerative heat exchanger is connected to the air inlet of the first-stage expander. The exhaust port of the first-stage expander is connected to the shell-side air inlet of the second-stage regenerative heat exchanger. The shell-side exhaust port of the second-stage regenerative heat exchanger is connected to the air inlet of the second-stage expander. The first-stage and second-stage expanders expand and do work, driving the generator to generate electricity.

[0011] In some embodiments, a condenser is connected between the three-stage compressor and the gas receiver.

[0012] In some embodiments, a dehydrator is provided inside the condenser near the condenser's exhaust port.

[0013] In some embodiments, the photovoltaic-driven compressed air energy storage system with multi-stage compression and segmented heat recovery further includes an ORC unit, wherein the exhaust port of the first-stage expander and the exhaust port of the second-stage expander are respectively connected to the air inlet of the ORC unit, and the ORC unit uses the waste heat from the exhaust gases of the first-stage and second-stage expanders to drive a generator for secondary power generation.

[0014] In some embodiments, the ORC unit includes an evaporator and a turbine. The evaporator has a pipe-side inlet, a pipe-side outlet, a shell-side inlet, and a shell-side outlet. The shell-side inlet of the evaporator is connected to the outlet of the primary expander and the outlet of the secondary expander, respectively. The pipe-side outlet of the evaporator is connected to the inlet of the turbine so that the high-temperature and high-pressure steam discharged from the evaporator expands and does work in the turbine to drive the generator to generate electricity. The outlet of the turbine is connected to the pipe-side inlet of the evaporator so that the low-temperature and low-pressure steam discharged from the turbine can be recycled. The shell-side outlet of the evaporator is connected to the inlet of the primary expander and the inlet of the secondary expander, respectively, so as to recycle the waste heat of the expander exhaust gas.

[0015] In some embodiments, the primary compressor includes a housing, a piston rod, a first piston, a second piston, and a drive mechanism. The housing has a compression chamber, and the rear end of the housing is connected to a packing chamber, which is in communication with the compression chamber. The housing has an intake port on one side of the compression chamber and an exhaust port on the other side. The compression chamber has two intake ports and two exhaust ports, located at the front and rear ends of the compression chamber, respectively. The two exhaust ports are located at the front and rear ends of the compression chamber, respectively. One end of the piston rod is fixedly connected to the first piston, and the other end of the piston rod is fixedly connected to the drive mechanism. The second piston is connected to the piston rod and located between the first piston and the drive mechanism. The drive mechanism drives the first piston to slide linearly within the compression chamber and simultaneously drives the second piston to slide linearly within the packing chamber, which is filled with packing material. The primary, secondary, and tertiary compressors have the same structure.

[0016] In some embodiments, the compression chamber divides the housing into an intake chamber and an exhaust chamber. The intake port of the housing is located in the intake chamber, and the exhaust port of the housing is located in the exhaust chamber. The intake port and exhaust port of the housing, as well as the two intake ports and two exhaust ports of the compression chamber, are each provided with a one-way valve to prevent gas backflow. The intake chamber and the compression chamber are connected through the two intake ports of the compression chamber, and the exhaust chamber and the compression chamber are connected through the two exhaust ports of the compression chamber.

[0017] In some embodiments, a spray cooling device is provided inside the compression chamber to cool the compression chamber.

[0018] In some embodiments, the gas storage tank includes an outer shell and an inner liner, the inner liner being connected to the inside of the outer shell, a vacuum insulation layer being filled between the inner liner and the outer shell, the gas storage tank having an air inlet and an air outlet, the air inlet and the air outlet being located on opposite sides of the gas storage tank, and a safety valve, a temperature sensor and a pressure sensor being connected to the gas storage tank, the safety valve, the temperature sensor and the pressure sensor extending into the inside of the inner liner.

[0019] In some embodiments, the exhaust port of the gas storage tank is connected to the inlet of the primary compressor to recycle the gas in the gas storage tank. A heat regenerator is connected to the connecting pipeline between the exhaust port of the gas storage tank and the inlet of the primary compressor to preheat the gas that needs to be recycled. Attached Figure Description

[0020] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings. in: Figure 1 This is a schematic diagram of the structure of a photovoltaic-driven compressed air energy storage system with multi-stage compression and segmented heat recovery according to an embodiment of the present invention; Figure 2 for Figure 1 A schematic diagram of the internal structure of the compressor in the image; Figure 3 for Figure 1 A schematic diagram of the structure of the gas storage tank in the image; Figure 4 for Figure 1 A schematic diagram of the ORC unit in the diagram; Figure 5 This is a logic diagram of the controller monitoring the compressor process according to an embodiment of the present invention; Figure label: 1. MPPT controller; 2. DC / DC converter; 3. Central controller; 4. Photovoltaic module; 5. Primary compressor; 6. Secondary compressor; 7. Tertiary compressor; 8. Primary thermal storage heat exchanger; 9. Secondary thermal storage heat exchanger; 10. Condenser; 11. Thermal regenerator; 12. Gas storage tank; 13. High-temperature thermal storage tank; 14. Low-temperature thermal storage tank; 15. Secondary regenerative heat exchanger; 16. Primary regenerative heat exchanger; 17. Primary expander; 18. Secondary expander; 19. Generator; 20. ORC unit; 21. Power grid; 501, First piston; 502, Compression chamber; 503, Packing chamber; 504, Second piston; 505, Piston rod; 1201. Inner liner; 1202. Vacuum insulation layer; 1203. Outer shell; 2001, Evaporator; 2002, Turbine. Detailed Implementation

[0021] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0022] The following description, with reference to the accompanying drawings, illustrates a photovoltaic-driven compressed air energy storage system with multi-stage compression and segmented heat recovery, according to embodiments of the present invention.

[0023] like Figure 1-4 As shown, this embodiment of the invention proposes a photovoltaic-driven compressed air energy storage system with multi-stage compression and segmented heat recovery, including: photovoltaic module 4, multi-stage compressor unit, primary heat storage heat exchanger 8, secondary heat storage heat exchanger 9, high-temperature heat storage tank 13, low-temperature heat storage tank 14, primary regenerative heat exchanger 16, secondary regenerative heat exchanger 15, primary expander 17 and secondary expander 18.

[0024] Photovoltaic module 4 is electrically connected to multi-stage compressor unit. Photovoltaic module 4 supplies power to multi-stage compressor unit. Multi-stage compressor unit includes primary compressor 5, secondary compressor 6 and tertiary compressor 7. Air is introduced into the air inlet of primary compressor 5. The exhaust port of primary compressor 5 is connected to the air inlet of secondary compressor 6. The exhaust port of secondary compressor 6 is connected to the air inlet of tertiary compressor 7. The exhaust port of tertiary compressor 7 is connected to air storage tank 12.

[0025] The primary heat storage heat exchanger 8 has a tube-side inlet and a tube-side outlet, as well as a shell-side inlet and a shell-side outlet. The primary heat storage heat exchanger 8 is connected to the connecting pipeline between the tube-side outlet of the primary compressor 5 and the tube-side inlet of the secondary compressor 6. The secondary heat storage heat exchanger 9 has a tube-side inlet and a tube-side outlet, as well as a shell-side inlet and a shell-side outlet. The secondary heat storage heat exchanger 9 is connected to the connecting pipeline between the tube-side outlet of the secondary compressor 6 and the tube-side inlet of the tertiary compressor 7.

[0026] The high-temperature heat storage tank 13 has an air inlet and an air outlet, and the low-temperature heat storage tank 14 has an air inlet and an air outlet. The shell-side air outlet of the first-stage heat storage heat exchanger 8 is connected to the air inlet of the high-temperature heat storage tank 13, and the air outlet of the high-temperature heat storage tank 13 is connected to the air inlet of the low-temperature heat storage tank 14. The air outlet of the low-temperature heat storage tank 14 is connected to the shell-side air inlet of the first-stage heat storage heat exchanger 8 and the shell-side air inlet of the second-stage heat storage heat exchanger 9, respectively. The air inlet of the high-temperature heat storage tank 13 is connected to the shell-side air outlet of the first-stage heat storage heat exchanger 8 and the shell-side air outlet of the second-stage heat storage heat exchanger 9, respectively.

[0027] The first-stage regenerative heat exchanger 16 has a tube-side air inlet and a tube-side air outlet, as well as a shell-side air inlet and a shell-side air outlet. The second-stage regenerative heat exchanger 15 has a tube-side air inlet and a tube-side air outlet, as well as a shell-side air inlet and a shell-side air outlet. The air outlet of the high-temperature heat storage tank 13 is connected to the tube-side air inlet of the first-stage regenerative heat exchanger 16 and the tube-side air inlet of the second-stage regenerative heat exchanger 15, respectively. The air inlet of the low-temperature heat storage tank 14 is connected to the tube-side air outlet of the first-stage regenerative heat exchanger 16 and the tube-side air outlet of the second-stage regenerative heat exchanger 15, respectively. The air outlet of the gas storage tank 12 is connected to the shell-side air inlet of the first-stage regenerative heat exchanger 16.

[0028] The shell-side exhaust port of the first-stage regenerative heat exchanger 16 is connected to the air inlet of the first-stage expander 17. The exhaust port of the first-stage expander 17 is connected to the shell-side air inlet of the second-stage regenerative heat exchanger 15. The shell-side exhaust port of the second-stage regenerative heat exchanger 15 is connected to the air inlet of the second-stage expander 18. The first-stage expander 17 and the second-stage expander 18 expand and do work, driving the generator 19 to generate electricity.

[0029] This invention achieves segmented heat storage by setting up a high-temperature heat storage tank 13 and a low-temperature heat storage tank 14. Segmented heat storage differs from traditional single-temperature heat storage methods; it allows for matched storage across different temperature ranges, enabling the stratified utilization of high-temperature and low-temperature heat, thereby significantly improving energy efficiency. While ensuring compression efficiency, it maximizes heat recovery and avoids the heat loss problems found in conventional CAES systems.

[0030] The system of this invention achieves an integrated process of "multi-stage compression - staged heat storage - high-pressure storage" during the compression stage. This not only effectively reduces the energy consumption and heat load of single-stage compression but also significantly improves the utilization rate of heat storage and the overall system safety. This innovative structure of staged compression and segmented heat recovery allows the system to flexibly adapt to fluctuations in photovoltaic output and provides a stable high-pressure gas source and adjustable heat source input for subsequent expansion work.

[0031] This invention, through its dual-stage regenerative and dual-expansion structure, effectively extends the energy release path of the high-pressure air, allowing it to perform work in stages during the gradual depressurization and cooling process, thus significantly improving expansion and energy conversion efficiency. The expanded low-pressure air can be recycled through a regenerative heat exchanger, further enhancing system energy efficiency.

[0032] This invention achieves efficient utilization and long-term energy storage of photovoltaic energy, significantly improving energy utilization and operational safety, and solving problems such as low efficiency, large heat loss, and insufficient regulation capacity in traditional compressed air energy storage systems. By employing direct photovoltaic power supply, the power chain is short, reducing energy conversion stages and increasing the proportion of photovoltaic energy consumption. During the discharge phase, stored heat and waste heat are fully utilized, avoiding reliance on external fossil fuels or electric heating.

[0033] Furthermore, the photovoltaic module 4 is electrically connected to the first-stage compressor 5 via the MPPT controller 1 and the DC / DC converter 2. The photovoltaic module 4 generates DC power under sunlight conditions. The MPPT controller 1 optimizes and regulates the current and voltage. The MPPT controller 1 tracks the maximum power point of the photovoltaic array in real time, sampling parameters including voltage, current, irradiance, and temperature, and dynamically adjusts the operating point using perturbation observation or model prediction algorithms. The DC / DC converter 2 performs voltage matching and stabilizes the output, providing power to the subsequent multi-stage compressor unit.

[0034] Furthermore, the DC / DC converter can adopt buck-boost topology, multiphase parallel topology, or LLC resonant structure, which can adapt to photovoltaic series-parallel configurations of different scales and effectively reduce ripple current.

[0035] Furthermore, the high-temperature heat storage tank 13 and the low-temperature heat storage tank 14 each include several heat storage devices, which can store gases with different temperature ranges. The multi-stage compression design allows the air to be pressurized step by step under different pressure and temperature conditions. At the same time, each exhaust end is coupled to the heat storage unit through a heat exchanger, avoiding the problem of uneven temperature distribution in a single heat storage unit.

[0036] Furthermore, the low-temperature thermal storage tank 14 is filled with a water-ethylene glycol mixture, an aluminum-based particle bed, or a phase change material (PCM), with a thermal storage temperature range of 50–200°C. The high-temperature thermal storage tank 13 is filled with molten salt, a high-temperature resistant ceramic honeycomb, or a silicon carbide particle bed, with a thermal storage temperature range of 300–600°C.

[0037] Furthermore, both the high-temperature heat storage tank 13 and the low-temperature heat storage tank 14 are provided with a vacuum insulation layer or an aerogel insulation layer on the outside to reduce heat transfer loss.

[0038] Furthermore, temperature, pressure, and flow sensors are installed at different locations in the high-temperature heat storage tank 13 and the low-temperature heat storage tank 14. These sensors can monitor the temperature distribution of each layer inside the heat storage tank in real time and track the movement of heat within the tank. This prevents excessively rapid heat mixing, which could cause the high-temperature and low-temperature zones to lose their stratification, ensuring that the stored heat can be effectively utilized according to different temperature levels. Each heat storage circuit is equipped with an electrically controlled valve and a bypass valve, facilitating the selection of appropriate temperature zones for heat output under different discharge requirements.

[0039] Furthermore, the electrical energy output by generator 19 is connected to the power grid 21 through the grid connection interface to achieve stable power supply.

[0040] Furthermore, the photovoltaic-driven compressed air energy storage system with multi-stage compression and segmented heat recovery also includes a central controller 3, which comprehensively manages the operation of the entire system. The central controller 3 collects real-time data on photovoltaic output, grid load, compressor status, gas storage pressure, and thermal storage temperature, and adjusts the parameters of control valves or equipment at each level to achieve flexible switching of operating conditions. For example, when photovoltaic output is high and grid load is low, the system automatically enters charging mode to maximize compression and energy storage; during peak grid periods, the system switches to releasing mode to release stored gas and thermal storage to achieve peak power generation; and when photovoltaic fluctuations are severe, the central controller 3 can coordinate the operation of some compressors or expanders to achieve rapid grid response.

[0041] Furthermore, both the primary expander 17 and the secondary expander 18 are multi-stage radial turbine or high-temperature screw type machines, which can be operated in single or dual parallel operation depending on the power level and operating conditions.

[0042] Furthermore, the entire system is equipped with multiple control valves, which are opened and closed by commands from the central controller 3, allowing for the regulation of the entire system and ensuring its safety and stability.

[0043] In some embodiments, such as Figure 2 As shown, a condenser 10 is connected between the three-stage compressor 7 and the gas storage tank 12.

[0044] In some embodiments, a dehydrator is provided inside the condenser 10 near the exhaust port of the condenser 10. This dehydrator removes moisture and oil mist during the compression process, ensuring the purity and stability of the stored air, preventing the risk of corrosion and condensation inside the air tank 12, and extending the service life of downstream valves, expanders, and other core components.

[0045] Understandably, multi-stage compression significantly increases air temperature, and the subsequent cooling process is often accompanied by water vapor condensation. If this is not removed in time, it will lead to condensation and corrosion inside the air tank 12, and may even cause valve freezing and pipe blockage.

[0046] In some embodiments, such as Figure 1 As shown, the photovoltaic-driven compressed air energy storage system with multi-stage compression and segmented heat recovery also includes an ORC unit 20. The exhaust ports of the first-stage expander 17 and the second-stage expander 18 are respectively connected to the air inlets of the ORC unit 20. The ORC unit 20 uses the waste heat from the exhaust gases of the first-stage expander 17 and the second-stage expander 18 to drive the generator 19 for secondary power generation.

[0047] This invention, through the configuration of ORC unit 20, achieves a dual-path collaborative mode of "expander main power generation + ORC auxiliary power generation": the expander undertakes the main power generation task, while ORC unit 20 fully utilizes the waste heat of the expander exhaust gas for supplementary power generation. This not only improves the utilization rate of waste heat and reduces heat dissipation losses, but also effectively enhances the overall round-trip efficiency of the system. The operating status of ORC unit 20 can be automatically adjusted according to the real-time changes in expander exhaust temperature and flow rate. During operation, when the expander exhaust temperature is high or the flow rate is large, ORC unit 20 increases its power to achieve additional electrical energy output; when the exhaust gas temperature decreases, ORC unit 20 automatically reduces its load to maintain cycle stability and thermal efficiency.

[0048] Compared to traditional CAES systems, this embodiment of the invention introduces an ORC unit 20 to convert previously unusable medium- and low-temperature waste heat into usable electrical energy, thereby improving the overall energy efficiency of the system by 5% to 10%. This ensures that the system not only has energy storage capabilities but also enables waste heat power generation, significantly improving energy utilization efficiency and economy, which aligns with the development direction of efficient utilization of clean energy.

[0049] It is understandable that after the expander completes the staged expansion of air, the temperature of the exhaust gas is usually still between 100 and 300°C. Direct discharge would result in a large amount of energy loss.

[0050] In some embodiments, such as Figure 4 As shown, the ORC unit 20 includes an evaporator 2001 and a turbine 2002. The evaporator 2001 has a pipe-side air inlet, a pipe-side air outlet, a shell-side air inlet, and a shell-side air outlet. The shell-side air inlet of the evaporator 2001 is connected to the exhaust outlet of the first-stage expander 17 and the exhaust outlet of the second-stage expander 18, respectively. The pipe-side air outlet of the evaporator 2001 is connected to the air inlet of the turbine 2002 so that the high-temperature and high-pressure steam discharged from the evaporator 2001 expands and does work in the turbine 2002, driving the generator 19 to generate electricity. The exhaust outlet of the turbine 2002 is connected to the pipe-side air inlet of the evaporator 2001 so that the low-temperature and low-pressure steam discharged from the turbine 2002 can be recycled. The shell-side air outlet of the evaporator 2001 is connected to the air inlet of the first-stage expander 17 and the air inlet of the second-stage expander 18, respectively, so as to recycle the waste heat of the expander exhaust gas.

[0051] The ORC working fluid is a low-boiling-point, high-thermal-stability organic compound (such as R245fa, R134a, isobutane, or propane). It is heated by the exhaust gas and vaporized into high-pressure steam within the evaporator 2001. This high-pressure steam enters the turbine 2002, expands, and performs work, driving the generator 19 to rotate, thus achieving secondary power generation. The low-temperature, low-pressure steam discharged from the turbine 2002 is then pumped back to the evaporator 2001, forming a closed thermodynamic cycle.

[0052] Furthermore, the evaporator 2001 is connected to a working fluid flow meter and a pressure sensor, which are respectively connected to the central controller 3. The central controller 3 dynamically adjusts the working fluid flow and turbine load according to the changes in the exhaust gas temperature and flow of the expander, so as to ensure that the ORC unit 20 and the main system maintain heat and power matching.

[0053] In some embodiments, such as Figure 2 As shown, the primary compressor 5 includes a housing, a piston rod 505, a first piston 501, a second piston 504, and a drive mechanism. The housing contains a compression chamber 502. The rear end of the housing is connected to a packing chamber 503, which communicates with the compression chamber 502. The housing has an intake port on one side of the compression chamber 502 and an exhaust port on the other side. The compression chamber 502 has two intake ports and two exhaust ports. The two intake ports are located at the front and rear ends of the compression chamber 502, respectively, and the two exhaust ports are located at the front and rear ends of the compression chamber 502, respectively. At the rear end, one end of the piston rod 505 is fixedly connected to the first piston 501, and the other end of the piston rod 505 is fixedly connected to the drive mechanism. The second piston 504 is connected to the piston rod 505 and is located between the first piston 501 and the drive mechanism. The drive mechanism drives the first piston 501 to slide linearly in the compression chamber 502, and at the same time drives the second piston 504 to slide linearly in the packing chamber 503. The packing chamber 503 is filled with packing to reduce leakage and wear caused by motion friction, thereby reducing energy consumption while ensuring airtightness. The structures of the first-stage compressor 5, the second-stage compressor 6, and the third-stage compressor 7 are the same.

[0054] By providing a second piston 504, this embodiment of the invention can enhance the mechanical support of the piston rod 505 within the packing cavity 503, enabling the piston rod 505 to maintain stable operation under high-pressure impact without displacement or vibration.

[0055] The compressor in this embodiment of the invention achieves a high compression ratio while ensuring high efficiency and stability of operation, enabling the compressor to run continuously for a long time without serious wear or failure, and significantly improving the reliability of the entire system during long-term operation.

[0056] Furthermore, the piston rod 505 is made of high-strength alloy steel or composite materials, which has good wear resistance and fatigue resistance. It can maintain strength and rigidity even in high-frequency reciprocating motion, ensuring the long service life of the compressor.

[0057] Furthermore, the packing material is made of high-temperature resistant and compression-resistant sealing material.

[0058] In some embodiments, such as Figure 2As shown, the compression chamber 502 divides the housing into an intake chamber and an exhaust chamber. The intake port of the housing is located in the intake chamber, and the exhaust port of the housing is located in the exhaust chamber. The intake port and exhaust port of the housing, as well as the two intake ports and two exhaust ports of the compression chamber 502, are each equipped with a one-way valve to prevent gas backflow. The intake chamber and the compression chamber 502 are connected through the two intake ports of the compression chamber 502, and the exhaust chamber and the compression chamber 502 are connected through the two exhaust ports of the compression chamber 502.

[0059] When the first-stage compressor 5 is running, the drive mechanism drives the first piston 501 to move to the right within the compression chamber 502. A negative pressure is created on the left side of the compression chamber 502. The one-way valve at the left-side intake port automatically opens after reaching the set opening pressure, allowing ambient air to enter the compression chamber 502 on the left side of the first piston 501. As the first piston 501 moves to the left, it compresses the air, gradually increasing the pressure in the left-side compression chamber 502. The one-way valve on the left side automatically opens after reaching the set opening pressure, and the high-pressure air is discharged through the exhaust port and sent to the second-stage compressor 6. Simultaneously, while the left side of the compression chamber 502 compresses the air, a negative pressure is created on the right side. The one-way valve at the right-side intake port automatically opens after reaching the set opening pressure, allowing ambient air to enter the compression chamber 502 on the right side of the first piston 501. As the first piston 501 moves to the right, it compresses the air, gradually increasing the pressure in the right-side compression chamber 502. The one-way valve on the right side automatically opens after reaching the set opening pressure, and the high-pressure air is discharged through the exhaust port and sent to the second-stage compressor 6.

[0060] The compressor in this embodiment of the invention can achieve bidirectional operation; when one side of the compression chamber 502 is performing a compression operation, the other side of the compression chamber 502 is performing a suction operation. This can improve the working efficiency of the compressor.

[0061] In some embodiments, the compression chamber 502 is provided with a spray cooling device to cool the compression chamber 502.

[0062] It should be noted that during the compression process, as the air is gradually compressed, the temperature inside the compression chamber 502 rises rapidly. To prevent excessive temperature from reducing compressor efficiency and damaging components, a spray cooling device is installed inside the compression chamber 502. Its nozzles directly spray coolant (such as deionized water or a specific coolant) into the compression chamber 502. The spray droplets come into full contact with the high-temperature air in a short time and absorb a large amount of heat, thereby significantly reducing the gas temperature inside the chamber. This direct spray cooling method is more efficient than traditional jacketed cooling, keeping the compression temperature rise within a reasonable range and improving the compression isentropic efficiency.

[0063] Furthermore, the spray cooling device is located at both ends of the compression chamber 502, which can set the limit position of the movement of the first piston 501 so that the first piston 501 will not come into contact with the spray cooling device.

[0064] Furthermore, the compressor's exhaust port is connected to a gas-liquid separator.

[0065] After being spray-cooled, the gas, carrying some coolant droplets, enters the gas-liquid separator through the exhaust port of compression chamber 502. The gas-liquid separator uses principles such as swirling flow, inertia, or gravitational settling to separate the droplets from the gas. The collected liquid is recycled back to the coolant system for reuse, while the dry air enters the next stage compressor for further pressurization. This process effectively prevents blade erosion or valve jamming caused by droplets entering the next stage compressor, ensuring long-term stable system operation.

[0066] This invention utilizes the synergistic effect of spray cooling and gas-liquid separation to form a closed cooling loop: the injected coolant lowers the temperature of the compression chamber 502, while the droplets carried out with the gas are separated and recovered, allowing the liquid to be recycled. This design reduces compression power consumption and extends the lifespan of vulnerable components such as valves and seals; furthermore, it ensures that the air entering the next stage compressor is low-temperature, low-humidity clean gas, thereby improving the overall efficiency and safety of the system.

[0067] In some embodiments, such as Figure 3 As shown, the gas storage tank 12 includes an outer shell 1203 and an inner liner 1201. The inner liner 1201 is connected to the inside of the outer shell 1203. A vacuum insulation layer 1202 is filled between the inner liner 1201 and the outer shell 1203. The gas storage tank 12 has an air inlet and an air outlet, which are located on opposite sides of the gas storage tank 12. A safety valve, a temperature sensor, and a pressure sensor are connected to the gas storage tank 12. The safety valve, temperature sensor, and pressure sensor extend into the inside of the inner liner 1201.

[0068] This invention incorporates a safety valve that automatically releases pressure in case of abnormal gas pressure, ensuring safe system operation. When the gas storage pressure exceeds the design limit, the safety valve automatically opens, releasing excess gas into the environment, thereby preventing the gas storage tank 12 from rupturing due to overpressure.

[0069] The gas storage tank 12 of this embodiment of the invention adopts a double-layer structure. The inner liner 1201 is used to directly withstand high-pressure air, while the outer shell 1203 provides additional mechanical strength and protection. The vacuum insulation layer 1202 can not only effectively reduce the heat loss generated during air compression, but also suppress the influence of the external ambient temperature on the gas state inside the gas storage tank 12, thereby maintaining the thermodynamic stability during the gas storage process.

[0070] In this embodiment of the invention, a pressure sensor is installed to measure the internal pressure changes of the inner liner 1201 in real time and transmit the signal to the central controller 3. When the pressure deviates from the set range, the central controller 3 will issue an audible and visual alarm and automatically execute commands to reduce load or switch the gas storage unit to ensure that the system operates within a safe range.

[0071] This invention, by incorporating a temperature sensor, can detect the temperature rise caused by the thermal effect of compressed air, thus preventing excessively high temperatures from degrading the performance of the inner liner 1201 material.

[0072] The air storage tank 12 of this invention not only enhances safety at the structural level, but also, compared with traditional compressed air energy storage devices, can automatically degrade operation, quickly depressurize, and provide real-time early warning under abnormal conditions, significantly improving the safety and reliability of operation.

[0073] Furthermore, multiple gas storage tanks 12 can be connected in parallel. Each gas storage tank 12 can be independently started, stopped, and vented in stages via an electrically controlled valve, avoiding cyclic fatigue caused by frequent charging and discharging of a single gas storage tank 12. The parallel arrangement also allows the remaining gas storage tanks 12 to continue operating while one gas storage tank 12 is under maintenance or decommissioned, thereby improving system redundancy and maintainability.

[0074] Furthermore, a check valve is connected to the gas storage pipeline to ensure unidirectional flow of compressed air, prevent backflow, and protect the safety of the upstream compressor and pipeline. At the same time, the check valve can also isolate the gas in emergencies, preventing interference between multiple gas storage tanks 12.

[0075] Furthermore, the safety valve is configured as a spring-loaded or pilot-operated structure and can form a dual protection system with the rupture disc. In extreme operating conditions, the rupture disc can serve as a last line of defense, rapidly releasing the internal high-pressure gas to ensure the safety of equipment and personnel.

[0076] Furthermore, the housing 1203 is connected to strain gauges or acoustic emission sensors for real-time monitoring of metal fatigue and potential crack formation, providing early warning of material degradation.

[0077] Furthermore, the inner liner 1201 can be made of 20MnMoNb high-strength steel or composite material wound tank, and the outer shell 1203 is a steel load-bearing shell.

[0078] In some embodiments, such as Figure 1 As shown, the exhaust port of the gas storage tank 12 is connected to the inlet of the first-stage compressor 5 to recycle the gas in the gas storage tank 12. A heat regenerator 11 is connected to the connecting pipe between the exhaust port of the gas storage tank 12 and the inlet of the first-stage compressor 5 to preheat the gas that needs to be recycled.

[0079] In some embodiments of the present invention, the heat exchangers and high-temperature heat storage tank 13 involved in the multi-stage compression and segmented heat recovery photovoltaic-driven compressed air energy storage system are lined with Inconel alloy, stainless steel, or ceramic to prevent high-temperature oxidation and thermal fatigue. All high-temperature pipelines are made of alloy steel or ceramic composite materials with a pressure resistance ≥10MPa and a temperature resistance ≥600℃. Control valves are all equipped with electric or pneumatic actuators, and a manual bypass is retained to ensure operability during maintenance. The measurement and control system adopts redundant communication and a dual PLC architecture, and key sensors are equipped with dual backups to improve overall reliability.

[0080] In some embodiments of the present invention, the operating parameters and control strategies involved in the photovoltaic-driven compressed air energy storage system with multi-stage compression and segmented heat recovery are as follows: the isentropic efficiency of the compressor is 0.75–0.85, the isentropic efficiency of the expander is 0.7–0.8, and the total UA value at the heat exchange end is optimized within the range of 2000–5000 W / K, enabling the system's round-trip efficiency to reach 55%–65% under cost constraints. The intelligent control strategy, combining mechanism modeling and data-driven approaches, can quickly adjust the operating mode when photovoltaic forecasts are insufficient or when grid load changes abruptly. For example, when photovoltaic forecasts decrease by more than 30%, the system automatically switches to an energy storage mitigation mode, with the expander operating at reduced capacity to ensure smooth grid power delivery.

[0081] In some embodiments of the present invention, the fault diagnosis and protection in a photovoltaic-driven compressed air energy storage system with multi-stage compression and segmented heat recovery is as follows: The system employs a mechanism-data hybrid diagnostic method. It monitors indicators such as compressor bearing temperature rise, heat exchanger pressure drop, tank leakage rate, valve jamming, and abnormal thermal front advancement. When an anomaly occurs, the control unit immediately triggers graded derating, switches bypass channels, and logs the changes, while simultaneously triggering audible and visual alarms and a remote monitoring interface. This design ensures the system has rapid self-healing capabilities under abnormal operating conditions.

[0082] like Figure 5 As shown, the compressor monitoring process is as follows: The central controller receives data on photovoltaic power, thermal storage tank temperature, and system temperature. It determines whether the photovoltaic power exceeds the current compression load requirement. If it does, the number of compression stages is increased to enhance heat recovery until the photovoltaic power falls below the current compression load requirement. Then, it checks whether the thermal storage tank temperature is greater than or equal to the upper limit. If it is, heat diversion is initiated to transfer heat externally and reduce the heat load accumulation. If it is less than the upper limit, heat storage continues to maintain thermal efficiency, and the compressor section is continuously monitored for any abnormalities. If an abnormality occurs, the compressor enters degraded operation or is shut down. The abnormal compressor stage is disconnected, emergency air cooling is used, the fault is recorded, and the number of compression stages is restored step by step, restoring the heat recovery mode until the compressor section returns to normal, maintaining the current compression and thermal management status.

[0083] The overall operation process of this invention includes the following steps: Photovoltaic module 4 generates DC power under sunlight. The MPPT controller 1 optimizes and regulates the current and voltage, and the DC / DC converter 2 performs voltage matching and stable output to power the subsequent compressor unit. During charging, atmospheric air is drawn in and compressed by the first-stage compressor 5. The compressed, high-temperature gas first enters the first-stage heat exchanger 8, transferring some heat to the high-temperature storage tank 13. The air after heat exchange is then introduced into the second-stage compressor 6, where it is pressurized again and enters the second-stage heat exchanger 9 for a second heat recovery, transferring some heat to the high-temperature storage tank 13. It then enters the third-stage compressor 7. After the third stage of compression, the air is cooled and dehumidified by the condenser 10, and the cooled and dehumidified air is then recycled into the storage tank 12.

[0084] Under energy release conditions, the high-pressure air in the gas storage tank 12 first absorbs high-temperature heat from the high-temperature heat storage tank 13 through the primary regenerative heat exchanger 16, and then enters the primary expander 17 to expand and do work, driving the generator 19 to generate electricity. The expanded air is then introduced into the secondary regenerative heat exchanger 15 to further absorb the heat released from the high-temperature heat storage tank 13, and then enters the secondary expander 18 for secondary expansion and power generation. After the two-stage expansion is completed, some of the waste heat from the exhaust gas enters the evaporator 2001 in the ORC unit 20 to drive the turbine 2002 for secondary power generation, realizing the utilization of waste heat. The high-temperature gas in the high-temperature heat storage tank 13, after heat exchange between the primary regenerative heat exchanger 16 and the secondary regenerative heat exchanger 15, is then introduced into the low-temperature heat storage tank 14 for heat recovery.

[0085] In this invention, the term "some embodiments," etc., refers to specific features, structures, materials, or characteristics described in connection with that embodiment, which are included in at least one embodiment of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiments. Furthermore, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments. Moreover, those skilled in the art can combine and integrate the different embodiments described in this specification and the features of the different embodiments without contradiction.

[0086] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A photovoltaic-driven compressed air energy storage system with multi-stage compression and segmented heat recovery, characterized in that, include: Photovoltaic modules; A multi-stage compressor unit, wherein the photovoltaic module is electrically connected to the multi-stage compressor unit, the photovoltaic module supplies power to the multi-stage compressor unit, the multi-stage compressor unit includes a primary compressor, a secondary compressor and a tertiary compressor, the air inlet of the primary compressor is introduced into the primary compressor, the exhaust port of the primary compressor is connected to the air inlet of the secondary compressor, the exhaust port of the secondary compressor is connected to the air inlet of the tertiary compressor, and the exhaust port of the tertiary compressor is connected to an air storage tank; A primary heat storage heat exchanger and a secondary heat storage heat exchanger, wherein the primary heat storage heat exchanger has a tube-side air inlet and a tube-side air outlet, as well as a shell-side air inlet and a shell-side air outlet, and the primary heat storage heat exchanger is connected to the connecting pipeline between the tube-side air outlet of the primary compressor and the tube-side air inlet of the secondary compressor. The secondary heat storage heat exchanger has a tube-side air inlet and a tube-side air outlet, as well as a shell-side air inlet and a shell-side air outlet. The secondary heat storage heat exchanger is connected to the connecting pipeline between the tube-side air outlet of the secondary compressor and the tube-side air inlet of the tertiary compressor. A high-temperature thermal storage tank and a low-temperature thermal storage tank are provided. The high-temperature thermal storage tank has an air inlet and an air outlet, and the low-temperature thermal storage tank has an air inlet and an air outlet. The shell-side air outlet of the first-stage thermal storage heat exchanger is connected to the air inlet of the high-temperature thermal storage tank, and the air outlet of the high-temperature thermal storage tank is connected to the air inlet of the low-temperature thermal storage tank. The air outlet of the low-temperature thermal storage tank is connected to the shell-side air inlet of the first-stage thermal storage heat exchanger and the shell-side air inlet of the second-stage thermal storage heat exchanger, respectively. The air inlet of the high-temperature thermal storage tank is connected to the shell-side air outlet of the first-stage thermal storage heat exchanger and the shell-side air outlet of the second-stage thermal storage heat exchanger, respectively. A primary regenerative heat exchanger and a secondary regenerative heat exchanger are provided. The primary regenerative heat exchanger has a tube-side air inlet and a tube-side air outlet, as well as a shell-side air inlet and a shell-side air outlet. The secondary regenerative heat exchanger also has a tube-side air inlet and a tube-side air outlet, as well as a shell-side air inlet and a shell-side air outlet. The air outlet of the high-temperature heat storage tank is connected to the tube-side air inlet of the primary regenerative heat exchanger and the tube-side air inlet of the secondary regenerative heat exchanger, respectively. The air inlet of the low-temperature heat storage tank is connected to the tube-side air outlet of the primary regenerative heat exchanger and the tube-side air outlet of the secondary regenerative heat exchanger, respectively. The air outlet of the gas storage tank is connected to the shell-side air inlet of the primary regenerative heat exchanger. The system comprises a primary expander and a secondary expander. The shell-side exhaust port of the primary regenerative heat exchanger is connected to the air inlet of the primary expander, and the exhaust port of the primary expander is connected to the shell-side air inlet of the secondary regenerative heat exchanger. The shell-side exhaust port of the secondary regenerative heat exchanger is connected to the air inlet of the secondary expander. The primary and secondary expanders perform expansion work, driving a generator to generate electricity.

2. The photovoltaic-driven compressed air energy storage system with multi-stage compression and segmented heat recovery according to claim 1, characterized in that, A condenser is connected between the three-stage compressor and the gas storage tank.

3. The photovoltaic-driven compressed air energy storage system with multi-stage compression and segmented heat recovery according to claim 2, characterized in that, A dehydrator is installed inside the condenser near the condenser's exhaust port.

4. The photovoltaic-driven compressed air energy storage system with multi-stage compression and segmented heat recovery according to claim 1, characterized in that, It also includes an ORC unit, wherein the exhaust port of the first-stage expander and the exhaust port of the second-stage expander are respectively connected to the air inlet of the ORC unit, and the ORC unit uses the waste heat of the exhaust gas from the first-stage expander and the second-stage expander to drive the generator for secondary power generation.

5. The photovoltaic-driven compressed air energy storage system with multi-stage compression and segmented heat recovery according to claim 4, characterized in that, The ORC unit includes an evaporator and a turbine. The evaporator has a pipe-side inlet, a pipe-side outlet, a shell-side inlet, and a shell-side outlet. The shell-side inlet of the evaporator is connected to the outlet of the first-stage expander and the outlet of the second-stage expander, respectively. The pipe-side outlet of the evaporator is connected to the inlet of the turbine so that the high-temperature and high-pressure steam discharged from the evaporator expands and does work in the turbine, driving the generator to generate electricity. The outlet of the turbine is connected to the pipe-side inlet of the evaporator so that the low-temperature and low-pressure steam discharged from the turbine can be recycled. The shell-side outlet of the evaporator is connected to the inlet of the first-stage expander and the inlet of the second-stage expander, respectively, so as to recycle the waste heat of the expander exhaust gas.

6. The photovoltaic-driven compressed air energy storage system with multi-stage compression and segmented heat recovery according to claim 1, characterized in that, The primary compressor includes a housing, a piston rod, a first piston, a second piston, and a drive mechanism. The housing has a compression chamber, and the rear end of the housing is connected to a packing chamber, which is in communication with the compression chamber. The housing has an intake port on one side of the compression chamber and an exhaust port on the other side. The compression chamber has two intake ports and two exhaust ports, located at the front and rear ends of the compression chamber, respectively. The two exhaust ports are located at the front and rear ends of the compression chamber, respectively. One end of the piston rod is fixedly connected to the first piston, and the other end is fixedly connected to the drive mechanism. The second piston is connected to the piston rod and located between the first piston and the drive mechanism. The drive mechanism drives the first piston to slide linearly within the compression chamber and simultaneously drives the second piston to slide linearly within the packing chamber, which is filled with packing material. The primary, secondary, and tertiary compressors have the same structure.

7. The photovoltaic-driven compressed air energy storage system with multi-stage compression and segmented heat recovery according to claim 6, characterized in that, The compression chamber divides the housing into an intake chamber and an exhaust chamber. The intake port of the housing is located in the intake chamber, and the exhaust port of the housing is located in the exhaust chamber. The intake port and exhaust port of the housing, as well as the two intake ports and two exhaust ports of the compression chamber, are each equipped with a one-way valve to prevent gas backflow. The intake chamber and the compression chamber are connected through the two intake ports of the compression chamber, and the exhaust chamber and the compression chamber are connected through the two exhaust ports of the compression chamber.

8. The photovoltaic-driven compressed air energy storage system with multi-stage compression and segmented heat recovery according to claim 6, characterized in that, The compression chamber is equipped with a spray cooling device to cool the compression chamber.

9. The photovoltaic-driven compressed air energy storage system with multi-stage compression and segmented heat recovery according to claim 1, characterized in that, The gas storage tank includes an outer shell and an inner liner. The inner liner is connected to the inside of the outer shell, and a vacuum insulation layer is filled between the inner liner and the outer shell. The gas storage tank has an air inlet and an air outlet, which are located on opposite sides of the gas storage tank. A safety valve, a temperature sensor, and a pressure sensor are connected to the gas storage tank, and the safety valve, the temperature sensor, and the pressure sensor extend into the inside of the inner liner.

10. The photovoltaic-driven compressed air energy storage system with multi-stage compression and segmented heat recovery according to claim 9, characterized in that, The exhaust port of the gas storage tank is connected to the inlet of the first-stage compressor to recycle the gas in the gas storage tank. A heat regenerator is connected to the connecting pipeline between the exhaust port of the gas storage tank and the inlet of the first-stage compressor to preheat the gas that needs to be recycled.

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