Photovoltaic-geothermal energy storage system physical model test device and method

Abstract

The invention discloses a photovoltaic-geothermal energy storage system physical model test device and method, and belongs to the technical field of laboratory simulation devices. Comprising a liquid storage tank, a high-pressure injection system, a fluid heating system, a rock core clamping system, a rock core constant temperature system, a confining pressure system, a liquid recovery system, an acoustic emission monitoring system, a temperature and pressure monitoring system, a permeability coefficient testing system and a pipeline connection system, according to the invention, the process that the high-temperature and high-pressure fluid is circularly injected into the rock to induce rock fracture and seepage heat transfer can be carried out, so that the actual working process that the photovoltaic heating fluid is stored into the geothermal energy storage stratum can be simulated, and the test that the high-temperature and high-pressure fluid is injected into the rock under different injection-production strategy conditions is carried out; the dynamic evolution characteristics of the temperature field in the rock and the change mechanism of the thermal damage of the reservoir surrounding rock under different injection-production strategies are defined, and corresponding technical theoretical support is provided for improving the energy storage efficiency of the photovoltaic-geothermal energy storage system to the maximum extent.

Description

Technical Field

[0001] The present invention belongs to the technical field of laboratory simulation devices, and in particular relates to a physical model test device and method for a photovoltaic-geothermal energy storage system. Background Art

[0002] Energy is an important foundation for maintaining economic development and social stability. With the improvement of world prosperity and the growth of global production, the demand for energy is increasing. Due to the defects of traditional fossil fuels such as limited reserves and serious pollution, under the dual challenges of growing energy demand and reducing carbon emissions, countries around the world have focused their attention on the development and utilization of clean renewable energy. In this environment, my country urgently needs to rapidly promote the clean and low-carbon transformation of energy through energy structure adjustment and the construction of a new power system. The development and utilization of renewable energy such as solar energy, hydropower, wind power, and geothermal energy will continue to grow.

[0003] The combination of photovoltaic power generation and energy storage systems can be a cheaper alternative to coal-fired power generation, and is also an option that is more compatible with the power grid. Geothermal energy storage has the advantages of large scale, low cost, wide application, and can be used across seasons, providing a unique way of photovoltaic power generation and energy storage. The photovoltaic-geothermal energy storage system uses solar radiation to heat the fluid, which is then injected into the sedimentary strata for storage, forming a high-temperature geothermal reservoir, and then used for geothermal power generation, heating and other cascade utilization. While solving the problem of power supply imbalance caused by the intermittent nature of solar energy, the system compensates for geothermal gradients, enhances the potential for geothermal power generation, and accelerates the construction of photovoltaic-geothermal energy storage systems. It can not only meet all-weather energy needs, but also maintain the stability and reliability of the power grid after being connected to the power grid.

[0004] When the fluid heated by solar radiation is injected into the geothermal reservoir formation, the surrounding rock of the injection channel will be damaged and fractured due to the influence of mass and heat transfer of high-temperature fluid. At present, the relevant research on photovoltaic geothermal energy storage system is in the initial exploration stage, and many processes are not yet mature, such as well network layout, injection and production process, etc. Simulating the operation process of photovoltaic-geothermal energy storage system in the laboratory has guiding significance for actual engineering, so it is very necessary to simulate the circulation injection and production of high-temperature fluid in geothermal reservoir indoors. At present, the research on rock thermal damage and fracture in indoor physical model experiments mostly directly heats the rock, injects low-temperature fluid into the rock, and monitors the change of temperature at the fluid outlet. It is impossible to accurately simulate the process of rock damage and fracture in geothermal reservoirs with a certain temperature when high-temperature fluid is injected. In addition, the current indoor test methods and means cannot accurately monitor the evolution process of surrounding rock damage and fracture in photovoltaic-geothermal energy storage system, so it is impossible to analyze the influence of rock thermal damage and fracture on photovoltaic-geothermal energy storage efficiency when solar thermal radiation fluid is injected into geothermal energy storage system. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a physical model test device and method for a photovoltaic-geothermal energy storage system to simulate the high-temperature and high-pressure fluid circulation injection and production process and the high-temperature fluid seepage heat transfer process. The test device and test method provide certain guidance for the analysis of the thermal damage behavior of the surrounding rock during the operation of the photovoltaic geothermal reservoir system, analyze the influence of different injection and production factors on the energy storage efficiency, and provide scientific and engineering guidance for the arrangement of various mining conditions of the actual photovoltaic geothermal energy storage system.

[0006] A physical model test device for a photovoltaic-geothermal energy storage system, comprising a liquid storage tank, a high-pressure injection system, a fluid heating system, a core clamping system, a core constant temperature system, a confining pressure system, a liquid recovery system, an acoustic emission monitoring system, a temperature and pressure monitoring system, a permeability coefficient testing system, and a pipeline connection system;

[0007] The liquid storage tank is connected to a high-pressure injection system, which includes a pump I, a pump II, and a controller, and injects fluid into the rock sample according to a set injection flow rate or injection pressure;

[0008] The fluid heating system includes two groups of pressure stabilizing tanks, and a heating device is arranged outside each group of pressure stabilizing tanks, one end of the pressure stabilizing tank is connected to the high-pressure injection system, and the other end is connected to the core clamping system;

[0009] The core clamping system is arranged inside the core constant temperature system. The core clamping system is a cylindrical barrel structure, and a high-temperature and high-pressure rubber sleeve is arranged inside. The rock sample is arranged inside the high-temperature and high-pressure rubber sleeve. The inlet end of the core clamping system is connected to the pressure-stabilizing tank, and the outlet end is connected to the back pressure valve I. The back pressure valve I is used to maintain the pressure in the fluid experiment to prevent the fluid from liquefying.

[0010] The acoustic emission monitoring system includes one or more acoustic emission probes, which are respectively arranged at both ends and around the rock sample;

[0011] The temperature and pressure monitoring system includes one or more temperature probes and pressure sensors. The temperature probes are respectively arranged at both ends and around the rock sample; the pressure sensors are arranged at both ends of the rock sample;

[0012] The permeability coefficient testing system includes two flow meters, which are respectively arranged at the inlet and outlet ends of the core clamping system;

[0013] The confining pressure system adopts a confining pressure pump, one end of which is connected to a liquid storage tank, and the other end is connected to a core clamping system. The confining pressure pump injects liquid between the high-temperature and high-pressure rubber sleeve and the cylindrical barrel to wrap the rock sample and uniformly apply confining pressure to the rock sample;

[0014] The liquid recovery system is provided with a refrigeration device, a coil is provided inside the refrigeration device, a temperature probe is provided at the tail end of the coil, and a pressure sensor is provided at the head end; the valve at the tail end of the back pressure valve II is connected to the liquid storage tank, and the interface is located at the upper end of the liquid storage tank. The liquid recovery system is used to provide a low temperature environment to cool the high temperature and high pressure liquid flowing through the back pressure valve I.

[0015] It also includes a data acquisition system for collecting data from an acoustic emission probe, a temperature probe, a pressure sensor and a flow meter.

[0016] The reference heat storage temperature of the fluid heating system is 200°C.

[0017] A photovoltaic-geothermal energy storage system physical model test method, using the photovoltaic-geothermal energy storage system physical model test device, includes the following steps:

[0018] Step 1: Cut the sandstone for the experiment and put it into the high-temperature and high-pressure rubber sleeve as a rock sample, place the high-temperature and high-pressure rubber sleeve inside the cylindrical barrel of the core clamping system, pass the temperature probe and the acoustic emission probe through the reserved holes of the cylindrical barrel and the high-temperature and high-pressure rubber sleeve, contact with the rock sample, seal the reserved holes, and close the test pipeline;

[0019] Step 2: Turn on the refrigeration switch of the liquid recovery system and set the refrigeration temperature; turn on the injection pump and valve I, and when the refrigeration device is filled with distilled water, close valve I and the injection pump; open the valve of the confining pressure system, start the confining pressure pump, inject the distilled water in the liquid storage tank into the core clamping system, wrap the high-temperature and high-pressure rubber sleeve, and apply confining pressure to the rock sample; turn on the heating device of the core constant temperature system to increase the temperature;

[0020] Step 3, inject distilled water into the pressure-stabilizing tank, heat the distilled water, maintain the pressure during the heating process, and keep the distilled water in the liquid phase; set the pressure of the back-pressure valve I; open the injection pump and valve II of the liquid recovery system, set the pressure of the back-pressure valve II, and the set pressure value is lower than the pressure of the back-pressure valve I; input the distilled water into the coil of the liquid return system, and when the pressure sensor in the refrigeration device indicates a value slightly lower than the pressure of the back-pressure valve II, close the injection pump and valve II;

[0021] Step 4: Inject distilled water heated to the set temperature into the rock sample. After the pressure sensor reading near the outlet is stable, stop injecting and store the high-temperature distilled water in the rock sample for a period of time. During this process, the temperature probe, pressure sensor and acoustic emission probe in the core clamping system transmit data to the data acquisition system in real time.

[0022] Step 5. After the interval time reaches the set value, the set pressures of back pressure valve I and back pressure valve II are reduced synchronously, so that the pressure set by back pressure valve I is lower than the indication of the pressure sensor at the outlet end. The high temperature and high pressure fluid in the core holder will flow into the liquid recovery system through back pressure valve I. When the indication of the temperature probe is lower than 100°C, open the connecting valve between the liquid recovery system and the liquid storage tank to cool down and reduce the pressure of the high temperature and high pressure liquid flowing through the liquid recovery system so as to recycle water resources. After the distilled water inside the entire experimental device is discharged, the rock sample is taken out, and the dynamic behavior characteristic test of the rock sample under the next test condition can be carried out.

[0023] Step 6. During the test, the fracture process of rock samples during high-temperature fluid injection is observed through acoustic emission data, and the evolution of the temperature field in the rock samples is monitored through temperature data to obtain rock fracture, temperature field evolution, heat storage efficiency under different injection schemes, as well as rock fracture mechanism and temperature field evolution law during high-temperature fluid injection.

[0024] Through the above-mentioned design scheme, the present invention can bring the following beneficial effects: the present invention provides a physical model test device and method for a photovoltaic-geothermal energy storage system, which can carry out the process of circulating high-temperature and high-pressure fluid injection into rocks to induce rock fracture and seepage heat transfer to simulate the actual workflow of photovoltaic heating fluid storage in geothermal energy storage formations. By carrying out experiments on high-temperature and high-pressure fluid injection into rocks under different injection and production strategies, the dynamic evolution characteristics of the temperature field in the rock and the change mechanism of thermal damage to the reservoir surrounding rock under different injection and production strategies can be clarified, so as to provide corresponding technical theoretical support for maximizing the energy storage efficiency of the photovoltaic-geothermal energy storage system.

[0025] The acoustic emission monitoring system in this test device can monitor the initiation and expansion of cracks in rocks during the injection of high-temperature fluids in real time.

[0026] The temperature monitoring system in this test device can monitor the fluid temperature at the inlet and outlet of the rock and the temperature at different positions around the rock in real time to characterize the evolution law of the rock and fluid temperature field.

[0027] The pressure monitoring system in this test device can monitor the changes in fluid pressure at the inlet and outlet of the rock in real time to determine the changes in the permeability characteristics of the rock.

[0028] The liquid recovery device in this experimental device can quickly cool the high-temperature and high-pressure fluid to ensure the recycling of the liquid and the safe and efficient conduct of the experiment. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention is further described below with reference to the accompanying drawings and specific embodiments:

[0030] Figure 1It is a structural schematic diagram of a physical model test device of a photovoltaic-geothermal energy storage system of the present invention.

[0031] Figure 2 It is a structural schematic diagram of a core clamping system of a physical model test device for a photovoltaic-geothermal energy storage system of the present invention.

[0032] Figure 3 It is a structural schematic diagram of a liquid recovery system of a physical model test device for a photovoltaic-geothermal energy storage system of the present invention.

[0033] In the figure, 1-liquid storage tank, 2-pump I, 3-pump II, 4-pressure stabilizing tank, 5-heating device, 6-core clamping system, 6-A-inlet end, 6-B-outlet end, 6-C-high temperature and high pressure rubber sleeve, 6-D-rock sample, 7-core constant temperature system, 8-confining pressure system, A-back pressure valve I, 9-liquid recovery system, 9-1-coil, 9-2-refrigeration device, 9-3-temperature probe, 9-4-pressure sensor, 9-5-connecting valve, B-back pressure valve II, 9-6-injection pump, 9-7-valve I, 9-8-valve II. DETAILED DESCRIPTION

[0034] A physical model test device for a photovoltaic-geothermal energy storage system comprises a liquid storage tank 1, a high-pressure injection system, a fluid heating system, a core clamping system 6, a core constant temperature system 7, a confining pressure system 8, a back pressure valve IA, a liquid recovery system 9, an acoustic emission monitoring system, a temperature and pressure monitoring system, a permeability coefficient testing system, a data acquisition system and a pipeline connection system.

[0035] The high-pressure injection system consists of two groups of pumps, namely pump I2, pump II3 and a controller. It has a constant speed working mode and a constant pressure working mode to choose from. Fluid can be injected into the rock sample according to the set injection flow rate or injection pressure. The dual pumps can alternately provide fluid to avoid interruption of fluid injection during the test.

[0036] The fluid heating system is used to generate high-temperature fluid, and is composed of two groups of high-temperature and high-pressure resistant pressure-stabilizing tanks 4 and a heating device 5. One end of the heating device 5 and the pressure-stabilizing tank 4 is connected to the high-pressure injection system, and the other end is connected to the core clamping system 6. Normal temperature fluid is injected into the pressure-stabilizing tank 4 through the high-pressure injection system, and after being heated to the set temperature by the fluid heating system, it is injected into the rock sample 6-D. The design of the two groups of pressure-stabilizing tanks 4 can ensure that the fluid maintains a stable high temperature when injected into the rock sample 6-D.

[0037] Furthermore, the heating system can heat the fluid in the storage tank 1 to 200°C, and the photovoltaic power generation device can heat the water to 400°C or even higher. However, in order to minimize potential operating problems and reduce costs, 200°C is selected as the reference heat storage temperature in the geothermal energy storage system.

[0038] Furthermore, the liquid storage tank 1 is provided with a high-precision pressure and temperature probe to monitor the pressure and temperature of the fluid in the liquid storage tank 1 .

[0039] The core clamping system 6 is composed of a cylindrical barrel and a high-temperature and high-pressure resistant rubber sleeve 6-C. The rock sample 6-D is placed in the rubber sleeve, and cylindrical pads are placed on both sides and placed in the cylindrical barrel together. Fixing devices are used on both sides of the cylindrical barrel to fix the rock sample 6-D. The inlet end 6-A of the core clamping system 6 is connected to the pressure-stabilizing tank 4, and the outlet end 6-B is connected to the back-pressure valve IA.

[0040] The back pressure valve IA is set to ensure that the fluid is always maintained above a certain pressure during the test. Since the fluid involves a relatively high temperature during the test, in order to ensure that the liquid is not vaporized, the fluid pressure needs to be maintained above a certain value.

[0041] In order to restore the photovoltaic-geothermal energy storage system to the greatest extent, the temperature of the surrounding rock around the reservoir is adjusted, which mainly depends on the core constant temperature system 7: the core clamping system 7 is placed in a constant temperature box, and the constant temperature box can maintain the ambient temperature at the value required by the project through a heating device.

[0042] The acoustic emission monitoring system consists of 9 acoustic emission probes, of which two acoustic emission probes are arranged at the inlet end 6-A and the outlet end 6-B of the core clamping system 6 respectively, and 5 acoustic emission probes are arranged around the rock sample to monitor the crack initiation and expansion process induced by the high-temperature fluid flowing through the rock sample.

[0043] The temperature and pressure monitoring system consists of temperature probes and pressure sensors, wherein five temperature probes are arranged around the rock sample 6-D to measure the temperature of the rock sample 6-D at different positions, and one temperature probe and one pressure sensor are arranged at the inlet end 6-A and the outlet end 6-B respectively to measure the temperature and pressure of the fluid at the inlet and outlet.

[0044] The permeability coefficient testing system is made up of two flowmeters, which are respectively arranged at the inlet end 6-A and the outlet end 6-B of the core clamping system 6 to measure the flow rate at the inlet and outlet of the fluid.

[0045] The confining pressure system 8 is composed of a confining pressure pump and a liquid storage tank 1. One end of the confining pressure pump is connected to the liquid storage tank 1, and the other end is connected to the core clamping system. The confining pressure pump injects liquid between the rubber sleeve and the cylindrical barrel to wrap the rock sample to uniformly apply confining pressure to the rock sample, and the applied confining pressure is reduced by pumping the liquid back to the liquid storage tank 1. The automatic servo system can automatically adjust the confining pressure to maintain a constant value during the test.

[0046] The liquid recovery system 9 is composed of a coil 9-1, a refrigeration device 9-2, a temperature probe 9-3, a pressure sensor 9-4, a back pressure valve ⅡB, a connecting valve 9-5, an injection pump 9-6, a valve Ⅰ 9-7 and a valve Ⅱ 9-8. The coil 9-1 is composed of a certain length of pipeline and is placed in the refrigeration device 9-2. The injection pump 9-6 in the liquid recovery system 9 is connected to the liquid storage tank 1. The refrigeration device 9-2 is used to provide a certain low temperature (between 0℃ and 5℃) liquid to promote the rapid cooling of the high temperature and high pressure liquid flowing through the back pressure valve ⅠA. A temperature probe 9-3 is set at the tail end of the coil 9-1. The back pressure valve ⅡB is used to control the temperature of the liquid flowing into the liquid storage tank. When the temperature drops below 100℃, the connecting valve 9-5 is opened to ensure the safe recovery of the liquid into the liquid storage tank 1.

[0047] The data acquisition system is composed of a data line and a computer, and can automatically collect data from the acoustic emission probe, temperature probe, pressure sensor and water flow rate, and transmit the data to the computer at intervals as needed for recording.

[0048] A physical model test method for a photovoltaic-geothermal energy storage system is as follows:

[0049] The sandstone obtained from the on-site system is cut into samples that meet the test size requirements and placed in a high-temperature and high-pressure rubber sleeve 6-C. The high-temperature and high-pressure rubber sleeve 6-C is placed in the core clamping system 6. The temperature probe and the acoustic emission probe are passed through the small circular holes reserved on the core clamping system 6 and the high-temperature and high-pressure rubber sleeve 6-C to contact the rock sample 6-D. The circular holes on the core clamping system 6 are closed with screw buckles and rubber rings to check the airtightness of the entire test pipeline.

[0050] Turn on the refrigeration switch in the liquid recovery system 9 and set the refrigeration temperature to 3°C.

[0051] Open the valve of the confining pressure system 8, set the target confining pressure (higher than the boiling point corresponding to the water temperature), start the confining pressure pump, inject the distilled water in the liquid storage tank 1 into the core clamping system 6 to wrap the high-temperature and high-pressure rubber sleeve 6-C to apply confining pressure to the rock sample 6-D, set the target temperature of the thermostat to 60°C, turn on the heating device of the core thermostat system 7 to start heating, and during the heating process of the thermostat, adjust the liquid volume in the core clamp and the rubber sleeve through the confining pressure system 8 to maintain a constant confining pressure.

[0052] According to the test plan, distilled water is injected into two pressure stabilizing tanks 4 at a certain flow rate through pumps Ⅰ2 and Ⅱ3. The target temperature in the pressure stabilizing tank 4 is set to 200℃ (the corresponding boiling point of distilled water is 6.25MPa), and the heating device 5 is turned on to heat the distilled water in the pressure stabilizing tank 4. At the same time, the pressure in the pressure stabilizing tank 4 is maintained above 12MPa to ensure that the distilled water is always maintained in the liquid phase during the heating process.

[0053] After the fluid in the pressure-stabilizing tank 4 reaches the target temperature, the pressure of the back pressure valve IA is kept consistent with the pressure set by the confining pressure system to ensure that the distilled water remains in liquid form during the entire test. At the same time, the pressure value of the back pressure valve ⅡB is set slightly lower than the back pressure valve IA but higher than the atmospheric pressure, and the injection pump 9-6 and valve Ⅰ9-7 in the liquid recovery system 9 are opened to input the distilled water into the refrigeration device 9-2. After the refrigeration device is filled with distilled water, valve Ⅱ9-8 is opened, valve Ⅰ9-7 is closed, and distilled water is injected into the coil 9-1. When the reading of the pressure sensor 9-4 in the refrigeration device is slightly lower than that of the pressure sensor close to the back pressure valve IA, the injection pump 9-6 and valve Ⅱ9-8 are closed.

[0054] Inject 200℃ distilled water into rock sample 6-D at the set injection flow rate. During the injection process, the temperature probe, pressure sensor and acoustic emission probe transmit data to the computer in real time. After the pressure sensor reading near the outlet 6-B stabilizes, stop the injection and store the high-temperature distilled water in the rock sample for a period of time. After the interval time reaches the set value, slowly and gradually reduce the setting values ​​of the back pressure valve IA and the back pressure valve ⅡB to be lower than the pressure sensor reading at the outlet of 6-B. When the temperature probe 9-3 reading is lower than 100 degrees Celsius, open the valve 9-5 connected to the liquid storage tank 1 in the liquid recovery system 9 to collect the distilled water into the liquid storage tank.

[0055] Replace the new rock sample, inject 200℃ distilled water into the rock sample again according to the test target injection flow rate, and carry out the next set of tests.

[0056] According to the above steps, design injection plans with different injection times, injection flow rates, injection temperatures, and interval times, implement high-temperature fluid injection, and record the monitoring data of the acoustic emission probe, temperature probe, pressure probe, and flow meter.

[0057] The fracture process of rock samples during high-temperature fluid injection is observed through acoustic emission data, and the evolution of the temperature field in the rock samples is monitored through temperature data. The similarities and differences in rock fracture, temperature field evolution and heat storage efficiency under different injection schemes are compared, the rock fracture mechanism and temperature field evolution law during high-temperature fluid injection are explained, the effects of injection times, injection temperature, injection flow rate, interval time, etc. on heat storage efficiency are revealed, and the photovoltaic-geothermal energy storage efficiency injection scheme is optimized.

Claims

1. A physical model test device for a photovoltaic-geothermal energy storage system, characterized by: It comprises a liquid storage tank (1), a high-pressure injection system, a fluid heating system, a core clamping system (6), a core constant temperature system (7), a confining pressure system (8), a liquid recovery system (9), an acoustic emission monitoring system, a temperature and pressure monitoring system, a permeability coefficient testing system and a pipeline connection system; The liquid storage tank (1) is connected to a high-pressure injection system, which includes a pump I (2), a pump II (3) and a controller, and injects fluid into the rock sample according to a set injection flow rate or injection pressure; The fluid heating system comprises two groups of pressure stabilizing tanks (4), and a heating device (5) is arranged outside each group of pressure stabilizing tanks (4), one end of the pressure stabilizing tank (4) is connected to the high-pressure injection system, and the other end is connected to the core clamping system (6); The core clamping system (6) is arranged inside the core constant temperature system (7); the core clamping system (6) is a cylindrical barrel structure, and a high-temperature and high-pressure rubber sleeve (6-C) is arranged inside; the rock sample (6-D) is arranged inside the high-temperature and high-pressure rubber sleeve (6-C); the inlet end (6-A) of the core clamping system (6) is connected to the pressure regulating tank (4), and the outlet end (6-B) is connected to the back pressure valve (9); the back pressure valve (9) is used to maintain pressure in the fluid experiment to prevent the fluid from liquefying; The acoustic emission monitoring system comprises one or more acoustic emission probes, which are respectively arranged at both ends and around the rock sample (6-D); The temperature and pressure monitoring system comprises one or more temperature probes and pressure sensors, wherein the temperature probes are respectively arranged at both ends and around the rock sample (6-D); and the pressure sensors are arranged at both ends of the rock sample (6-D); The permeability coefficient testing system comprises two flow meters, which are respectively arranged at the inlet end (6-A) and the outlet end (6-B) of the core clamping system (6); The confining pressure system (8) uses a confining pressure pump, one end of which is connected to the liquid storage tank (1), and the other end of which is connected to the core clamping system (6). The confining pressure pump injects liquid between the high-temperature and high-pressure rubber sleeve (6-C) and the cylindrical barrel to wrap the rock sample (6-D) and uniformly apply confining pressure to the rock sample; The liquid recovery system (9) is provided with a refrigeration device, a coil (9-1) is provided inside the refrigeration device, and a temperature probe (9-3) is provided at the tail end of the coil (9-1); a pressure sensor (9-4) is provided at the head end; a valve (9-5) is connected to the liquid storage tank (1) at the tail end of the back pressure valve II (B), and the interface is located at the upper end of the liquid storage tank (1); the liquid recovery system (9) is used to provide a low temperature environment to cool the high temperature and high pressure liquid flowing through the back pressure valve I (A).

2. A photovoltaic-geothermal energy storage system physical model test device according to claim 1, characterized in that: It also includes a data acquisition system for collecting and storing data from acoustic emission probes, temperature probes, pressure sensors, flow meters and temperature sensors.

3. A photovoltaic-geothermal energy storage system physical model test device according to claim 1, characterized in that: The reference heat storage temperature of the fluid heating system is 200°C.

4. A physical model test method for a photovoltaic-geothermal energy storage system, characterized by: The photovoltaic-geothermal energy storage system physical model test device according to claim 1 comprises the following steps: Step 1: Cut the sandstone for the experiment as a rock sample (6-D) and place it in a high-temperature and high-pressure rubber sleeve (6-C), place the high-temperature and high-pressure rubber sleeve (6-C) inside the cylindrical barrel of the core clamping system (6), pass the temperature probe and the acoustic emission probe through the reserved holes of the cylindrical barrel and the high-temperature and high-pressure rubber sleeve (6-C), contact with the rock sample (6-D), seal the reserved holes, and close the test pipeline; Step 2: Turn on the refrigeration switch of the liquid recovery system (9) and set the refrigeration temperature; turn on the injection pump (9-6) and valve I (9-7), and when the refrigeration device is filled with distilled water, close the valve (9-7) and the injection pump (9-6); open the valve of the confining pressure system (8), start the confining pressure pump, inject the distilled water in the liquid storage tank (1) into the core clamping system (6), wrap the high-temperature and high-pressure rubber sleeve (6-C), and apply confining pressure to the rock sample; turn on the heating device of the core constant temperature system (7) to increase the temperature; Step 3, inject distilled water into the pressure stabilizing tank (4), heat the distilled water, maintain the pressure during the heating process, and keep the distilled water in the liquid phase; set the pressure of the back pressure valve Ⅰ (A); open the injection pump (9-6) and valve Ⅱ (9-8) of the liquid recovery system (9), set the pressure of the back pressure valve Ⅱ (B), and the set pressure value is lower than the pressure of the back pressure valve Ⅰ (A); input the distilled water into the coil (9-1) of the liquid return system (9), and when the pressure sensor (9-4) in the refrigeration device (9-2) indicates a value slightly lower than the pressure of the back pressure valve Ⅱ (B), close the injection pump (9-6) and valve Ⅱ (9-8); Step 4: inject distilled water heated to a set temperature into the rock sample (6-D), and stop injecting after the pressure sensor reading near the outlet end (6-B) stabilizes, so that the high-temperature distilled water is stored in the rock sample for a period of time. During the storage process, the temperature probe, pressure sensor and acoustic emission probe in the core clamping system (6) transmit data to the data acquisition system in real time; Step 5: After the interval time reaches the set value, the set pressures of the back pressure valve Ⅰ(A) and the back pressure valve ⅡB() are simultaneously reduced, so that the pressure set by the back pressure valve Ⅰ(A) is lower than the reading of the pressure sensor at the outlet end (6-B); the high temperature and high pressure fluid in the core clamping system will flow into the liquid recovery system through the back pressure valve Ⅰ(A); when the reading of the temperature probe (9-3) is lower than 100°C, the connecting valve (9-5) between the liquid recovery system (9) and the liquid storage tank (1) is opened to reduce the temperature and pressure of the high temperature and high pressure liquid flowing through the liquid recovery system (9) and recycle water resources; after the distilled water in the entire experimental device is discharged, the rock sample (6-D) is taken out, and the dynamic behavior characteristic test of the rock sample under the next test condition is carried out; Step 6. During the test, the fracture process of the rock sample (6-D) during the injection of high-temperature fluid is observed through acoustic emission data, and the evolution of the temperature field in the rock sample is monitored through temperature data to obtain rock fracture, temperature field evolution, heat storage efficiency under different injection schemes, as well as rock fracture mechanism and temperature field evolution law during high-temperature fluid injection.

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