Compressed air-fused salt combined energy storage photovoltaic-photothermal-fuel backup complementary power generation system

Abstract

A compressed air-fused salt combined energy storage photovoltaic-photo-thermal-fuel backup complementary power generation system comprises a photovoltaic power generation panel, a cooling tower, a multi-stage cooler, a multi-stage isothermal compressor, a heat recovery device, a compressed air storage tank, a reservoir, a multi-stage isothermal expansion machine, a multi-stage countercurrent heat exchanger, a high-temperature fused salt tank, a low-temperature fused salt tank, a photo-thermal tower and a heliostat field. And a combustion furnace and a fused salt coil pipe are arranged. According to the system, photovoltaic power generation, compressed air energy storage, fused salt energy storage and photo-thermal power generation technologies are integrated, and efficient conversion and storage of energy are achieved. Through the three working cycle processes of sunny day energy storage, night power generation and cloudy day fuel backup power generation, the system can achieve stable supply of renewable energy sources, improve the energy utilization efficiency and reduce dependence on fossil energy, and has wide application prospects and market value.

Description

Technical Field

[0001] This utility model belongs to the field of energy storage technology, and specifically relates to a compressed air-molten salt combined energy storage photovoltaic-photothermal-fuel backup complementary power generation system. Background Technology

[0002] Against the backdrop of the current global energy structure transitioning towards cleaner and renewable energy, the large-scale application of renewable energy sources such as photovoltaics and wind power has become an inevitable trend. However, the inherent instability and uncertainty of these renewable energy sources affect the continuity and stability of energy supply, while also posing challenges to the safe operation of the power grid. Although our unit has successfully developed a hydraulic balance isothermal cycle energy storage power generation system (application number: 2024108305209) and a coal-fired energy storage power generation system (application number: 2024214667166), which have addressed the instability and uncertainty of renewable energy to some extent, these technologies mainly rely on electricity converted from photovoltaic and wind power for green energy utilization, while neglecting the direct utilization of other renewable energy sources such as solar thermal power. Furthermore, there are still certain limitations in terms of backup energy, limited to providing stable energy support when renewable energy supply is insufficient or interrupted, and unable to achieve a backup power effect completely similar to that of a diesel generator.

[0003] Therefore, this application proposes a photovoltaic, solar thermal, and fuel backup complementary power generation mode, aiming to achieve stable and direct utilization of renewable energy, further improve energy efficiency, and ensure the continuity and stability of energy supply. Through the design of backup energy, it achieves a backup effect similar to that of a diesel generator. This utility model will provide strong support for the global energy structure transformation, promote the widespread application of renewable energy, and has significant practical implications and broad market prospects. Summary of the Invention

[0004] This invention provides a compressed air-molten salt combined energy storage photovoltaic-solar thermal-fuel backup complementary power generation system, integrating photovoltaic power generation, compressed air energy storage, molten salt energy storage, and solar thermal power generation technologies. It organically combines the energy storage power generation system and the backup energy system, forming a novel energy supply model. This model not only addresses the instability and uncertainty of renewable energy but also allows for flexible adjustment of energy supply strategies according to actual needs, achieving efficient energy utilization and optimized allocation.

[0005] The specific description is as follows: A compressed air-molten salt combined energy storage photovoltaic-solar thermal-fuel backup complementary power generation system includes photovoltaic panels, a cooling tower, a multi-stage cooler, a multi-stage isothermal compressor, a heat recovery device, a compressed air storage tank, a water storage tank, a multi-stage isothermal expander, a multi-stage counter-current heat exchanger, a high-temperature molten salt tank, a low-temperature molten salt tank, a solar thermal tower, a heliostat field, a first clutch, a second clutch, an electric motor, a generator, a hydraulic generator, a first molten salt pump, a second molten salt pump, a cooling water pump, a booster pump, and connecting pipes between them; the electric motor, the multi-stage isothermal compressor, the multi-stage isothermal expander, and the generator are mounted on the same rotating shaft;

[0006] The first clutch is installed between the multi-stage isothermal compressor and the multi-stage isothermal expander;

[0007] The second clutch is installed between the electric motor and the multi-stage isothermal compressor;

[0008] The working fluid inlet of the first stage of the multi-stage isothermal compressor is directly connected to the environment, and the working fluid outlet of the last stage is connected to the inlet of the working fluid channel of the compressed air storage tank and the heat recovery device; the hydraulic generator and the booster pump are connected in parallel between the bottom of the compressed air storage tank and the bottom of the water storage tank; the compressed air storage tank is connected to the working fluid channel inlet of the heat recovery device through a pipeline, and the outlet of the working fluid channel of the heat recovery device is connected to the working fluid inlet of the first stage countercurrent heat exchanger of the multi-stage countercurrent heat exchanger; the exhaust gas channel inlet of the heat recovery device is connected to the exhaust gas outlet of the last stage of the multi-stage isothermal expander.

[0009] A cooler is installed between every two compression stages in the multi-stage isothermal compressor.

[0010] The multi-stage countercurrent heat exchanger is installed on the working fluid pipeline between every two expansion stages of the multi-stage isothermal expander or on the working fluid pipeline between the heat recovery device and the first expansion stage of the multi-stage isothermal expander.

[0011] The inlet of each stage of the multi-stage countercurrent heat exchanger is connected to the outlet of the second molten salt pump, the inlet of the second molten salt pump is connected to the high-temperature molten salt storage tank, and the outlet of each stage of the multi-stage countercurrent heat exchanger is connected to the low-temperature molten salt storage tank; the first molten salt pump is connected between the low-temperature molten salt storage tank and the solar thermal tower, and the high-temperature molten salt storage tank is directly connected to the solar thermal tower.

[0012] Furthermore, it also includes a combustion furnace and a molten salt coil; the molten salt coil is evenly arranged in the combustion furnace, one end of the molten salt coil is connected to the outlet of the first molten salt pump, the inlet of the first molten salt pump is connected to the low-temperature molten salt storage tank, and the other end of the molten salt coil is connected to the high-temperature molten salt storage tank.

[0013] Furthermore, it also includes a multi-stage combustion chamber, wherein the combustion chamber is installed on the working fluid pipeline between every two expansion stages of the multi-stage isothermal expander or on the working fluid pipeline between the heat recovery device and the first expansion stage of the multi-stage isothermal expander.

[0014] Furthermore, the working fluid inlet of the first-stage combustion chamber of the multi-stage combustion chamber is connected to the outlet of the working fluid channel of the heat recovery device; the inlets / outlets of the combustion chambers other than the first-stage combustion chamber of the multi-stage combustion chamber are respectively connected to the working fluid outlet of the previous expansion stage / the working fluid inlet of the next expansion stage of the multi-stage isothermal expander.

[0015] Furthermore, the cooling water channels, cooling water pumps, and cooling towers of the multi-stage cooler are connected by pipes to form a cooling water circulation system. The inlet and outlet of the air medium channel of the multi-stage cooler are respectively connected to the working fluid outlet of the previous compression stage and the working fluid inlet of the next compression stage of the multi-stage isothermal compressor.

[0016] Furthermore, the first-stage countercurrent heat exchanger of the multi-stage countercurrent heat exchanger is installed on the working fluid pipeline between the working fluid channel of the heat recovery device and the first expansion stage of the multi-stage isothermal expander; the inlet / outlet of the other countercurrent heat exchangers of the multi-stage countercurrent heat exchanger, except for the first-stage countercurrent heat exchanger, are respectively connected to the working fluid outlet of the previous expansion stage / the working fluid inlet of the next expansion stage of the multi-stage isothermal expander.

[0017] Furthermore, the fuel in the combustion furnace is one or more of the following: coal, pulverized coal, biomass, coal gas, natural gas, hydrogen, and liquid fuel.

[0018] Furthermore, the fuel in the multi-stage combustion chamber is one of coal gas, natural gas, hydrogen, or liquid fuel.

[0019] Furthermore, the electric motor is a DC motor, which is connected to multiple series and parallel photovoltaic panels. At the same time, the DC motor drives a multi-stage isothermal compressor to compress air for energy storage.

[0020] Furthermore, it also includes a wind turbine unit, which replaces the photovoltaic panels and is electrically connected to an electric motor.

[0021] This invention employs a combined strategy of photovoltaics, solar thermal, and fuel. During sunny days, it utilizes photovoltaic power generation, compressed air charging, and solar thermal equipment to heat low-temperature molten salt into high-temperature molten salt, achieving both photovoltaic compressed air energy storage and solar thermal molten salt energy storage. At night, it generates electricity through heat exchange between high-pressure air and molten salt via an expander. On cloudy or rainy days, it provides a backup energy system by mixing compressed air with fuel for combustion and expansion, ensuring stable energy support and continuity of energy supply during emergencies such as power shortages, insufficient or interrupted renewable energy supply, and a lack of available stored energy. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Appendix Figure 1 This is a schematic diagram of the structure of the new utility model of a compressed air-molten salt combined energy storage photovoltaic-solar thermal-fuel backup complementary power generation system.

[0024] Appendix Figure 2 This is a schematic diagram of the structure of the solar daytime energy storage process of this utility model.

[0025] Appendix Figure 3 This is a schematic diagram of the nighttime power generation process of this utility model.

[0026] Appendix Figure 4 This is a schematic diagram of the structure of the fuel backup power generation process in cloudy weather according to this utility model. Figure 1 .

[0027] Appendix Figure 5 This is a schematic diagram of the structure of the fuel backup power generation process in cloudy weather according to this utility model. Figure 2 .

[0028] The numbers in the above diagram represent the following: 1. Photovoltaic panel; 2. Cooling tower; 3. Multistage cooler; 4. Multistage isothermal compressor; 5. Heat recovery device; 6. Compressed air storage tank; 7. Water storage tank; 8. Multistage combustion chamber; 9. Multistage isothermal expander; 10. Multistage countercurrent heat exchanger; 111. High-temperature molten salt tank; 112. Low-temperature molten salt tank; 12. Solar thermal tower; 13. Heliostat field; 141. First clutch; 142. Second clutch; 151. Electric motor; 152. Generator; 153. Hydraulic generator; 161. First molten salt pump; 162. Second molten salt pump; 163. Cooling water pump; 164. Booster pump; 171~1711. Valves; 18. Combustion furnace; 19. Molten salt coil. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions of this utility model will be described in detail below.

[0030] Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments.

[0031] Based on the embodiments of this utility model, all other implementation methods obtained by those skilled in the art without inventive effort are within the scope of protection of this utility model. To facilitate understanding of the embodiments, various embodiments or implementation methods are provided below to illustrate the related devices, modules, and functions of this utility model.

[0032] To enable readers of this embodiment to quickly understand the implementation of this utility model, the appendix is ​​first described below. Figure 1 The working principle expressed is explained.

[0033] As attached Figure 1 As shown, a compressed air-molten salt combined energy storage photovoltaic-solar thermal-fuel backup complementary power generation system includes a photovoltaic power generation panel 1, a cooling tower 2, a multi-stage cooler 3, a multi-stage isothermal compressor 4, a heat recovery device 5, a compressed air storage tank 6, a water storage tank 7, a multi-stage combustion chamber 8, a multi-stage isothermal expander 9, a multi-stage countercurrent heat exchanger 10, a high-temperature molten salt tank 111, a low-temperature molten salt tank 112, a solar thermal tower 12, a heliostat field 13, a first clutch 141, a second clutch 142, an electric motor 151, a generator 152, a hydraulic generator 153, a first molten salt pump 161, a second molten salt pump 162, a cooling water pump 163, a booster pump 164, a combustion furnace 18, molten salt coils 19, and connecting pipes between them. The electric motor 151, the multi-stage isothermal compressor 4, the multi-stage isothermal expander 9, and the generator 152 are mounted on the same rotating shaft. A first clutch 141 connects the multi-stage isothermal compressor 4 and the multi-stage isothermal expander 9, allowing for a disengaged rotational connection between them. The electric motor 151 is a DC motor; the generator 152 is an AC generator, driven by the multi-stage isothermal expander 9. The DC motor 151 is connected to multiple series-parallel photovoltaic panels 1. A second clutch 142 connects the DC motor 151 to the multi-stage isothermal compressor 4, allowing for a disengaged rotational connection between them. Thus, the DC motor 151 can drive the AC generator 152 to generate electricity, acting as a motor inverter; simultaneously, the DC motor 151 drives the multi-stage isothermal compressor 4 to compress air for energy storage.

[0034] Please refer to Figure 2 As shown, the function of the multi-stage isothermal compressor 4 is to draw in working fluid air and perform multi-stage isothermal compression on the working fluid air to increase the pressure of the working fluid. The multi-stage isothermal compressor 4 has n (n≥2) compression stages, which are the first compression stage 41, the second compression stage 42, ..., the final compression stage 4n.

[0035] The function of the multi-stage cooler 3 is to dissipate the heat generated by the isothermal compressor 1 to the outside, so that the compression process is kept at a low temperature and achieves an approximate "isothermal compression". It has n-1 coolers, namely the first-stage cooler 31, the second-stage cooler 32, ..., the final-stage cooler 3n-1. Each cooler is installed on the working fluid pipeline between every two compression stages of the multi-stage isothermal compressor 4.

[0036] Please refer to Figures 3-5 As shown, the multi-stage isothermal expander 9 has m (m≥2) expansion stages, which are the first expansion stage 91, the second expansion stage 92, ..., the final expansion stage 9m.

[0037] The multi-stage counter-current heat exchanger 10 has m counter-current heat exchangers corresponding one-to-one with the expansion stages of the multi-stage isothermal expander 9, namely, the first-stage counter-current heat exchanger 101, the second-stage counter-current heat exchanger 102, the third-stage counter-current heat exchanger 103, ..., the final-stage counter-current heat exchanger 10m. The counter-current heat exchangers of the multi-stage counter-current heat exchanger 10 are installed on the working fluid pipeline between every two expansion stages of the multi-stage isothermal expander 9 or on the working fluid pipeline between the heat recovery device 5 and the first-stage isothermal expander 91 of the multi-stage isothermal expander 9.

[0038] The multi-stage combustion chamber 8 has m combustion chambers corresponding one-to-one with the expansion stages of the multi-stage isothermal expander 9, namely, the first-stage combustion chamber 81, the second-stage combustion chamber 82, the third-stage combustion chamber 83, ..., the final-stage combustion chamber 8m. The combustion chambers of the multi-stage combustion chamber 8 are installed on the working fluid pipeline between every two expansion stages of the multi-stage isothermal expander 9 or on the working fluid pipeline between the heat recovery device 5 and the first-stage isothermal expander 91 of the multi-stage isothermal expander 9.

[0039] The working fluid inlet of the first stage 41 of the multi-stage isothermal compressor 4 is directly connected to the environment, and the working fluid outlet of its last stage 4n is connected to the inlet of the working fluid channel of the compressed air storage tank 6 and the heat recovery device 5. The hydraulic generator 153 and the booster pump 164 are connected in parallel between the bottom of the compressed air storage tank 6 and the bottom of the water storage tank 7. The compressed air storage tank 6 is connected to the working fluid channel inlet of the heat recovery device 5 through a pipeline. The outlet of the working fluid channel of the heat recovery device 5 is connected to the working fluid inlet of the first stage countercurrent heat exchanger 101 of the multi-stage countercurrent heat exchanger 10 and the first stage combustion chamber 81 of the multi-stage combustion chamber 8, respectively. The exhaust gas channel inlet of the heat recovery device 5 is connected to the exhaust gas outlet of the last stage 9m of the multi-stage isothermal expander 9.

[0040] A multi-stage cooler 3 is installed between every two compressors in the multi-stage isothermal compressor 4. The inlet / outlet of the air medium channel of the multi-stage cooler 3 is connected to the working fluid outlet of the previous compression stage / the working fluid inlet of the next compression stage of the multi-stage isothermal compressor 4, respectively. The cooling water channel, cooling water pump 163, and cooling tower 2 of the multi-stage cooler 3 are connected by pipes to form a cooling water circulation system. The cooling water dissipates the heat generated by each compression stage of the multi-stage isothermal compressor 4 to the outside through the cooler of the multi-stage cooler 3, so that the compression process is kept at a low temperature, achieving an approximate "isothermal compression".

[0041] The countercurrent heat exchangers of the multi-stage countercurrent heat exchanger 10 are installed on the working fluid pipeline between every two expansion stages of the multi-stage isothermal expander 9 or on the working fluid pipeline between the heat recovery device 5 and the first expansion stage 91 of the multi-stage isothermal expander 9. That is, the first countercurrent heat exchanger 101 is installed on the working fluid pipeline between the working fluid channel of the heat recovery device 5 and the first expansion stage 91 of the multi-stage isothermal expander 9. The inlets / outlets of the other countercurrent heat exchangers of the multi-stage countercurrent heat exchanger 10, except for the first countercurrent heat exchanger 101, are respectively connected to the working fluid pipeline between the working fluid outlet of the previous expansion stage and the working fluid inlet of the next expansion stage of the multi-stage isothermal expander 9. The molten salt medium inlet of each stage of the multi-stage countercurrent heat exchanger 10 is connected to the outlet of the second molten salt pump 162, the inlet of the second molten salt pump 162 is connected to the high-temperature molten salt storage tank 111, and the outlet of each stage of the multi-stage countercurrent heat exchanger 10 is connected to the low-temperature molten salt storage tank 112. The first molten salt pump 161 is connected between the low-temperature molten salt storage tank 112 and the solar thermal tower 12, and the high-temperature molten salt storage tank 111 is directly connected to the solar thermal tower 12. In this way, the first molten salt pump 161 transports the low-temperature molten salt from the low-temperature molten salt storage tank 112 after heat exchange to the absorber of the solar thermal tower 12. The solar thermal tower 12 receives sunlight reflected by the heliostats in the heliostat field 13 to heat the low-temperature molten salt into high-temperature molten salt, which is then stored in the high-temperature molten salt storage tank 111.

[0042] The molten salt coils 19 are evenly arranged in the combustion furnace 18. One end of the molten salt coil 19 is connected to the outlet of the first molten salt pump 161 via valve 1710, and the inlet of the first molten salt pump 161 is connected to the low-temperature molten salt storage tank 112. The other end of the molten salt coil 19 is connected to the high-temperature molten salt storage tank 111 via valve 1211. In this way, the first molten salt pump 161 transports the low-temperature molten salt from the low-temperature molten salt storage tank 112 to the molten salt coils 19 in the combustion furnace 18. Simultaneously, fuel is fed into the combustion furnace 18 for complete combustion, heating the low-temperature molten salt in the molten salt coils 19 in the combustion furnace 18 into high-temperature molten salt, which is then stored in the high-temperature molten salt storage tank 111. The fuel in the combustion furnace 18 can be coal, pulverized coal, biomass, coal gas, natural gas, hydrogen, liquid fuel, etc.

[0043] The combustion chambers of the multi-stage combustion chamber 8 are installed on the working fluid pipeline between every two expansion stages of the multi-stage isothermal expander 9 or on the working fluid pipeline between the heat recovery device 5 and the first expansion stage 91 of the multi-stage isothermal expander 9. That is, the first-stage combustion chamber 81 is installed on the working fluid pipeline between the working fluid channel of the heat recovery device 5 and the first expansion stage 91. The inlets / outlets of the other combustion chambers of the multi-stage combustion chamber 8, except for the first-stage combustion chamber 81, are respectively connected to the working fluid outlet of the previous expansion stage / the working fluid inlet of the next expansion stage of the multi-stage isothermal expander 9. The working fluid outlet of the final expansion stage 9m is connected to the exhaust gas inlet of the heat recovery device 5.

[0044] The function of the compressed air storage tank 6 is to store / release compressed air medium that has undergone multi-stage isothermal compression. The function of the hydraulic generator 153 is to stabilize the pressure of the compressed air entering the compressed air storage tank 6 and to recover part of the energy of the compressed air; in this process, high-pressure compressed air enters the compressed air storage tank 6, and the water in the compressed air storage tank 6 is forced outward under the action of high-pressure gas. The discharged high-pressure water drives the hydraulic generator 153 to operate and generate electricity.

[0045] The function of the pressurization pump 164 is to inject water into the compressed air storage tank 6, and the water compresses the air in the compressed air storage tank 6 so that it enters the heat recovery device 5.

[0046] The function of the heat recovery device 5 is to recover the heat of the high-temperature exhaust gas from the final expansion stage 9m of the multi-stage isothermal expansion stage 9, and to use the recovered heat for preheating the compressed air before it does work; that is, the high-pressure, low-temperature compressed air exchanges heat with the exhaust gas discharged from the final expansion stage 9m in the heat recovery device 5. The high-pressure, low-temperature compressed air absorbs the heat of the exhaust gas and is preheated once, and then enters the first-stage countercurrent heat exchanger 101 or the first-stage combustion chamber 81.

[0047] Each combustion chamber of the multi-stage combustion chamber 5 is quantitatively injected with fuel, which mixes with the circulating working fluid and air entering the combustion chamber and is then fully combusted to produce exhaust gas. Each expansion stage of the multi-stage isothermal expander 9 is connected to a combustion chamber, which is driven by the exhaust gas produced in the combustion chamber to generate electricity.

[0048] The fuel in the combustion chamber 5 is coal gas, natural gas, hydrogen, liquid fuel, etc.

[0049] The power generation system of this utility model has three working cycles: daytime energy storage on sunny days, nighttime power generation, and fuel backup power generation on cloudy days.

[0050] During the daytime when there is abundant solar energy, please refer to... Figure 2As shown, the energy storage process includes two parts. The first is compressed air energy storage, where a portion of the electricity from the photovoltaic panel 1 drives a multi-stage isothermal compressor 4 via an electric motor 151 to compress and store air, achieving an efficient conversion of mechanical energy into compressed air potential energy. The second is solar thermal energy storage via a tower-type solar thermal system.

[0051] The working cycle of compressed air energy storage is as follows: The first stage 41 of the multi-stage isothermal compressor 4 draws in working air from the atmosphere and compresses it, causing both the temperature and pressure of the working air to rise. To prevent the working air temperature from rising too much, the working air that has been pressurized by the first stage 41 directly enters the first stage cooler 31 of the multi-stage cooler for cooling. After cooling, the first-pressurized working air enters the second stage 42 for secondary pressurization. After secondary pressurization, the working air enters the second stage cooler 32 for cooling. This process continues until the final stage 4n compresses the air to the predetermined pressure, after which it directly enters the compressed air storage tank 6. The water in the compressed air storage tank 6 is discharged from the compressed air storage tank 6 under the action of high-pressure gas, driving the hydraulic generator 153 to operate and generate electricity. The water output from the outlet of the hydraulic generator 153 finally enters the water storage tank 7, thus completing the energy storage process. During this process, the cooling tower 2 provides a continuous supply of cooling water to each stage of the multi-stage condenser 3 via the cooling water pump 163, dissipating the heat generated by each compression stage of the multi-stage isothermal compressor 4 to the outside, keeping the compression process at a low temperature and achieving approximate "isothermal compression".

[0052] The working cycle of the tower-type solar thermal system's solar thermal energy storage is as follows: Low-temperature molten salt in the low-temperature molten salt storage tank 112 is pumped by the first molten salt pump 161 to the absorber at the top of the solar thermal tower 12. The heliostat field 13 focuses sunlight onto the absorber at the top of the solar thermal tower 12, where the absorber converts light energy into heat energy, heating the molten salt to a high temperature. The high-temperature molten salt, propelled by the first molten salt pump 161, then enters the high-temperature molten salt storage tank 111 for storage.

[0053] Nighttime power generation process:

[0054] When renewable energy is unavailable at night, compressed air in compressed air storage tank 6 is released through pipelines to exchange heat with high-temperature molten salt in multi-stage counter-current heat exchanger 10, absorbing the heat from the molten salt and providing sufficient energy for subsequent power generation, thus providing stable and efficient power support. Figure 3As shown, the nighttime power generation cycle is as follows: The pressurization pump 164 injects water into the compressed air storage tank 6 to compress the air inside the tank and allow it to circulate back (this process increases the compressed air pressure). The compressed air directly enters the heat recovery device 5, where it exchanges heat with the high-temperature exhaust gas discharged from the final expansion stage 9m of the multi-stage isothermal expander 9. The compressed air absorbs the heat from the high-temperature exhaust gas and then enters the compressed air channel of the first-stage counter-current heat exchanger 101 of the multi-stage counter-current heat exchanger 10. Simultaneously, under the action of the second molten salt pump 162, the high-temperature molten salt in the high-temperature molten salt storage tank 111 is sent into the molten salt medium channel of the first-stage counter-current heat exchanger 101, transferring the heat of the high-temperature molten salt to the compressed air. After absorbing the heat from the high-temperature molten salt, the compressed air drives the first-stage expansion stage 91 of the multi-stage isothermal expander 9 to perform work. The compressed air then cools and depressurizes after performing work. The cooled and depressurized compressed air discharged from the first-stage expansion stage 91 of the multi-stage isothermal expander 9... The compressed air enters the secondary countercurrent heat exchanger 102 of the multi-stage countercurrent heat exchanger 10. The cooled and depressurized compressed air discharged from the first expansion stage 91 is heated by the high-temperature molten salt from the high-temperature molten salt storage tank 111 in the secondary countercurrent heat exchanger 102. Then, the heated compressed air drives the secondary expansion stage 92 of the multi-stage isothermal expander 9 to generate power and do work, and then cools and depressurizes again. In this way, before each expansion stage of the multi-stage isothermal expander 9 is driven by the working fluid of the power generation cycle, it first undergoes a heating process (that is, the working fluid of the power generation cycle is heated by the high-temperature molten salt from the high-temperature molten salt storage tank 111 in the corresponding countercurrent heat exchanger). The heated working fluid of the power generation cycle drives the expansion stage of the corresponding multi-stage isothermal expander 9 to generate power for power generation, until the last expansion stage 9m of the multi-stage isothermal expander 9. The exhaust gas discharged from the last expansion stage 9m of the multi-stage isothermal expander 9 directly enters the heat recovery device 5 for heat recovery, and the exhaust gas discharged from the heat recovery device 5 directly enters the air. This cyclical process completes the entire cycle.

[0055] In order to achieve approximately isothermal expansion, the compressed air first enters the counter-current heat exchanger connected to each expansion stage of the multi-stage isothermal expander 9 before entering each expansion stage. This heat exchangers exchange heat with the high-temperature molten salt exiting the high-temperature molten salt storage tank 111, absorbing heat from the molten salt to drive the corresponding expansion stage of the multi-stage isothermal expander 9 to perform work.

[0056] like Figure 4 As shown, the first step of fuel backup power generation on a cloudy day:

[0057] First, the first molten salt pump 161 transports the low-temperature molten salt from the low-temperature molten salt storage tank 112 to the molten salt coil 19 in the combustion furnace 18. At the same time, fuel is sent into the combustion furnace 18 for complete combustion, heating the low-temperature molten salt in the molten salt coil 19 in the combustion furnace 18 into high-temperature molten salt, which is then stored in the high-temperature molten salt storage tank 111, thus completing the molten salt heat storage.

[0058] Secondly, the first stage 41 of the multi-stage isothermal compressor 4 draws in working air from the atmosphere for compression, causing both the temperature and pressure of the working air to rise. To prevent the working air temperature from rising too much, the working air, after being pressurized in the first stage 41, directly enters the first stage cooler 31 of the multi-stage cooler for cooling. After cooling, the first-pressurized working air enters the second stage 42 for secondary pressurization, and after secondary pressurization, it enters the second stage cooler 32 for further cooling. This process continues until the final stage 4n compresses the working air to the predetermined pressure. The compressed working fluid air directly enters the heat recovery device 5, where it exchanges heat with the high-temperature exhaust gas discharged from the final expansion stage 9m of the multi-stage isothermal expander 9. Then, it enters the compressed air passage of the first-stage counter-current heat exchanger 101 of the multi-stage counter-current heat exchanger 10. Simultaneously, under the action of the second molten salt pump 162, the high-temperature molten salt in the high-temperature molten salt storage tank 111 is sent into the molten salt medium passage of the first-stage counter-current heat exchanger 101, transferring the heat of the high-temperature molten salt to the compressed air. The compressed air absorbs the heat from the high-temperature molten salt and drives the multi-stage isothermal expander. The first expansion stage 91 of the multi-stage isothermal expander 9 performs work, and the compressed air after performing work is cooled and depressurized. The cooled and depressurized compressed air discharged from the first expansion stage 91 of the multi-stage isothermal expander 9 enters the secondary counter-current heat exchanger 102 of the multi-stage counter-current heat exchanger 10. The cooled and depressurized compressed air discharged from the first expansion stage 91 is heated by the high-temperature molten salt from the high-temperature molten salt storage tank 111 in the secondary counter-current heat exchanger 102. Then, the heated compressed air drives the secondary expansion stage 92 of the multi-stage isothermal expander 9 to generate power and perform work, and then cools and depressurizes again. In this way, the working fluid of the power generation cycle is repeated each time. Before each expansion stage of the multi-stage isothermal expander 9 is driven, a heating process is first performed (i.e., the power generation cycle working fluid is heated in the corresponding counter-current heat exchanger by the high-temperature molten salt from the high-temperature molten salt storage tank 111). The heated power generation cycle working fluid drives the corresponding expansion stage of the multi-stage isothermal expander 9 to generate power, until the last expansion stage 9m of the multi-stage isothermal expander 9. The exhaust gas discharged from the last expansion stage 9m of the multi-stage isothermal expander 9 directly enters the heat recovery device 5 for heat recovery, and the exhaust gas discharged from the heat recovery device 5 directly enters the air. This cycle repeats continuously, completing the backup power generation process.

[0059] Cloudy Day Fuel Backup Power Generation Process Two:

[0060] like Figure 5As shown, the first stage 41 of the multi-stage isothermal compressor 4 draws in working air from the atmosphere for compression, causing both the temperature and pressure of the working air to rise. To prevent the working air temperature from rising too much, the working air, after being pressurized in the first stage 41, directly enters the first stage cooler 31 of the multi-stage cooler for cooling. After cooling, the first-pressurized working air enters the second stage 42 for secondary pressurization, and after secondary pressurization, it enters the second stage cooler 32 for further cooling. This process continues until the final stage 4n of the compressor reaches the predetermined pressure, after which it directly enters the heat recovery device 5. In the heat recovery device 5, it exchanges heat with the high-temperature exhaust gas discharged from the final stage 9m of the multi-stage isothermal expander 9. The compressed air absorbs the heat from the high-temperature exhaust gas and then enters the first stage combustion chamber 81 of the multi-stage combustion chamber 8. At the same time, fuel is injected into the first stage combustion chamber 81 and mixed with the compressed air entering the combustion chamber. After complete combustion, primary exhaust gas is generated. The first expansion stage 91 of the multi-stage isothermal expander 9 is connected to the first combustion chamber 81 of the multi-stage combustion chamber 8. The first expansion stage 91 of the multi-stage isothermal expander 9 is driven by the incoming primary exhaust gas and generates power and work, followed by cooling and depressurization of the primary exhaust gas. The cooled and depressurized primary exhaust gas discharged from the first expansion stage 91 of the multi-stage isothermal expander 9 enters the second combustion chamber 81 of the multi-stage combustion chamber 8, mixes with the injected fuel, and is fully combusted again to generate secondary exhaust gas. The secondary exhaust gas then enters the second expansion stage 92 of the multi-stage isothermal expander 9. The second expansion stage 92 is driven and generates power and work, followed by cooling and depressurization of the secondary exhaust gas. This process continues until the final expansion stage 9m of the multi-stage isothermal expander 9. The final expansion stage 9m is driven and generates power and work, followed by cooling and depressurization of the final exhaust gas. The final exhaust gas is not directly discharged into the air, but directly enters the heat recovery device 5 for heat recovery. The temperature of the final exhaust gas discharged from the heat recovery unit 5 is close to the ambient temperature, and it is directly discharged into the environment, thus completing the cloudy day fuel backup power generation cycle.

[0061] As described above, during energy storage and power generation, the multi-stage isothermal expander 9 drives the alternator 152 to generate electricity. During backup power generation, a starting power supply is first provided to the multi-stage isothermal compressor 4, and then the multi-stage isothermal expander 9 simultaneously drives the alternator 152 and the multi-stage isothermal compressor 4.

[0062] As described above, in the power generation system, because the multi-stage isothermal compressor is divided into three stages, and the temperature rise of each compression stage is limited to a small temperature difference, coupled with the use of a cooler to lower the temperature of the compressed working fluid after each compression, the process of "isothermal compression" is approximately achieved. Similarly, in isothermal expansion, the working fluid in each expansion stage of the multi-stage isothermal expander is heated before operation, achieving an approximate "isothermal expansion" process. This makes the entire thermodynamic process relatively close to the "Carnot cycle," thus achieving a relatively high system thermal efficiency.

[0063] By employing a multi-stage expansion accompanied by multi-stage heating, the working fluid can maintain a higher temperature and a higher average temperature throughout the entire expansion process, compared to single-stage or few-stage expansion. According to the Carnot cycle principle, the higher this temperature, the higher the efficiency of the thermodynamic system. Similarly, through multi-stage compression and heat dissipation cooling, the compression process is maintained at a lower temperature, achieving approximately "isothermal compression," which also improves the efficiency of the thermodynamic system. By comparing the highest efficiency of the theoretical cycle, the efficiency improvement potential of this invention can be understood.

[0064] In addressing the significant challenge of complementary and combined power generation from renewable energy sources, this invention employs a combined strategy of photovoltaics, solar thermal, and fuel. During sunny days, photovoltaic power generation, compressed air charging, and solar thermal equipment heating low-temperature molten salt to high-temperature molten salt enable photovoltaic compressed air energy storage and solar thermal molten salt energy storage. At night, high-pressure air and molten salt exchange heat to generate electricity via an expander. On cloudy or rainy days, a backup energy system generates electricity through the combustion and expansion of a mixture of compressed air and fuel. This system provides stable energy support and ensures the continuity of energy supply during emergencies such as power shortages, insufficient or interrupted renewable energy supply, and a lack of available energy storage.

Claims

1. A compressed air-molten salt combined energy storage photovoltaic-solar thermal-fuel backup complementary power generation system, characterized in that, The system includes photovoltaic panels, cooling towers, multi-stage coolers, multi-stage isothermal compressors, heat recovery devices, compressed air storage tanks, water storage tanks, multi-stage isothermal expanders, multi-stage counter-current heat exchangers, high-temperature molten salt tanks, low-temperature molten salt tanks, solar thermal towers, heliostat fields, first clutches, second clutches, electric motors, generators, hydraulic generators, first molten salt pumps, second molten salt pumps, cooling water pumps, booster pumps, and connecting pipes between them; the electric motor, multi-stage isothermal compressor, multi-stage isothermal expander, and generator are mounted on the same rotating shaft. The first clutch is installed between the multi-stage isothermal compressor and the multi-stage isothermal expander; The second clutch is installed between the electric motor and the multi-stage isothermal compressor; The working fluid inlet of the first stage of the multi-stage isothermal compressor is directly connected to the environment, and the working fluid outlet of the last stage is connected to the inlet of the working fluid channel of the compressed air storage tank and the heat recovery device; the hydraulic generator and the booster pump are connected in parallel between the bottom of the compressed air storage tank and the bottom of the water storage tank; the compressed air storage tank is connected to the working fluid channel inlet of the heat recovery device through a pipeline, and the outlet of the working fluid channel of the heat recovery device is connected to the working fluid inlet of the first stage countercurrent heat exchanger of the multi-stage countercurrent heat exchanger; the exhaust gas channel inlet of the heat recovery device is connected to the exhaust gas outlet of the last stage of the multi-stage isothermal expander. A cooler is installed between every two compression stages in the multi-stage isothermal compressor. The multi-stage countercurrent heat exchanger is installed on the working fluid pipeline between every two expansion stages of the multi-stage isothermal expander or on the working fluid pipeline between the heat recovery device and the first expansion stage of the multi-stage isothermal expander. The inlet of each stage of the multi-stage countercurrent heat exchanger is connected to the outlet of the second molten salt pump, the inlet of the second molten salt pump is connected to the high-temperature molten salt storage tank, and the outlet of each stage of the multi-stage countercurrent heat exchanger is connected to the low-temperature molten salt storage tank; the first molten salt pump is connected between the low-temperature molten salt storage tank and the solar thermal tower, and the high-temperature molten salt storage tank is directly connected to the solar thermal tower.

2. The compressed air-molten salt combined energy storage photovoltaic-solar thermal-fuel backup complementary power generation system as described in claim 1, characterized in that, It also includes a combustion furnace and molten salt coils; the molten salt coils are evenly arranged in the combustion furnace, one end of the molten salt coils is connected to the outlet of the first molten salt pump, the inlet of the first molten salt pump is connected to the low-temperature molten salt storage tank, and the other end of the molten salt coils is connected to the high-temperature molten salt storage tank.

3. The compressed air-molten salt combined energy storage photovoltaic-solar thermal-fuel backup complementary power generation system as described in claim 1, characterized in that, It also includes a multi-stage combustion chamber, wherein the combustion chamber is installed on the working fluid pipeline between every two expansion stages of the multi-stage isothermal expander or on the working fluid pipeline between the heat recovery device and the first expansion stage of the multi-stage isothermal expander.

4. A compressed air-molten salt combined energy storage photovoltaic-solar thermal-fuel backup complementary power generation system as described in claim 3, characterized in that, The working fluid inlet of the first-stage combustion chamber of the multi-stage combustion chamber is connected to the outlet of the working fluid channel of the heat recovery device; the inlets / outlets of the combustion chambers other than the first-stage combustion chamber of the multi-stage combustion chamber are respectively connected to the working fluid outlet of the previous expansion stage / the working fluid inlet of the next expansion stage of the multi-stage isothermal expander.

5. A compressed air-molten salt combined energy storage photovoltaic-solar thermal-fuel backup complementary power generation system as described in claim 1, characterized in that, The cooling water channels, cooling water pumps, and cooling towers of the multi-stage cooler are connected by pipes to form a cooling water circulation system. The inlet and outlet of the air medium channel of the multi-stage cooler are respectively connected to the working fluid outlet of the previous compression stage and the working fluid inlet of the next compression stage of the multi-stage isothermal compressor.

6. A compressed air-molten salt combined energy storage photovoltaic-solar thermal-fuel backup complementary power generation system as described in claim 1, characterized in that, The first countercurrent heat exchanger of the multi-stage countercurrent heat exchanger is installed on the working fluid pipeline between the working fluid channel of the heat recovery device and the first expansion stage of the multi-stage isothermal expander; the inlet / outlet of the other countercurrent heat exchangers of the multi-stage countercurrent heat exchanger, except for the first countercurrent heat exchanger, are respectively connected to the working fluid outlet of the previous expansion stage / the working fluid inlet of the next expansion stage of the multi-stage isothermal expander.

7. A compressed air-molten salt combined energy storage photovoltaic-solar thermal-fuel backup complementary power generation system as described in claim 2, characterized in that, The fuel in the combustion furnace is one or more of the following: coal, pulverized coal, biomass, coal gas, natural gas, hydrogen, and liquid fuel.

8. A compressed air-molten salt combined energy storage photovoltaic-solar thermal-fuel backup complementary power generation system as described in claim 3, characterized in that, The fuel in the multi-stage combustion chamber is one of coal gas, natural gas, hydrogen, or liquid fuel.

9. A compressed air-molten salt combined energy storage photovoltaic-solar thermal-fuel backup complementary power generation system as described in claim 1, characterized in that, The motor is a DC motor, which is connected to multiple series and parallel photovoltaic panels. At the same time, the DC motor drives a multi-stage isothermal compressor to compress air for energy storage.

10. A compressed air-molten salt combined energy storage photovoltaic-solar thermal-fuel backup complementary power generation system as described in claim 1, characterized in that, It also includes wind turbine units, which replace photovoltaic panels and are electrically connected to motors.

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