A multi-mode dual-channel photovoltaic-photothermal integrated system

Abstract

This invention discloses a multi-mode dual-channel photovoltaic-thermal integrated system, belonging to the field of solar energy and photovoltaic thermal management technology. The system constructs a sandwich-style dual-channel thermal management structure on the back of the photovoltaic module, coupling near-panel liquid heat exchange, composite phase change heat storage, and back-side finned air heat exchange. The composite phase change material layer comprises organic phase change material, expanded graphite, and rice husk charcoal, with a mass ratio of 65~75:20~28:4~8. Liquid heat exchange channels are embedded on one side of the composite phase change material layer; heat dissipation fins are attached to the back of the composite phase change material layer and extend into the airflow channel. Under the control of the control unit, the system can switch between four operating modes: passive phase change heat storage, liquid heat extraction, air heat exchange regeneration, and liquid-air synergistic cooling, achieving uniform cooling, rapid regeneration of the phase change material, and cascade utilization of waste heat. This invention significantly reduces the peak temperature of the photovoltaic panel and improves temperature uniformity and overall energy utilization efficiency.

Description

Technical Field

[0001] This invention relates to the field of solar energy and photovoltaic thermal management technology, specifically to a multi-mode dual-channel photovoltaic-thermal integrated system that integrates compounded biomass-shaped composite phase change materials. Background Technology

[0002] Solar energy, as a clean and renewable energy source, boasts significant advantages such as wide availability and zero pollution. Photovoltaic power generation, as an important form of solar energy utilization, has become a crucial source of electricity. However, in the photoelectric conversion process of crystalline silicon photovoltaic cells, only a portion of solar radiation is converted into electrical energy, with the remainder primarily converted into heat, leading to increased panel temperature. The photoelectric conversion efficiency of photovoltaic cells decreases with rising temperature, and prolonged exposure to excessively high temperatures or uneven temperature distribution accelerates the aging of encapsulation materials and shortens module lifespan. Therefore, continuous, uniform, and low-energy-consumption thermal management of photovoltaic modules is necessary.

[0003] Existing photovoltaic heat dissipation technologies mainly include active cooling and passive cooling. While active water cooling or forced air cooling has high heat exchange efficiency, it usually requires external power such as water pumps and fans, which leads to parasitic energy consumption. At the same time, single-fluid cooling is prone to forming temperature gradients along the fluid flow direction, resulting in uneven temperature distribution on the panel surface. Although passive cooling does not require additional power, it is limited by ambient temperature, natural wind speed, and heat dissipation area, making it difficult to maintain a stable cooling effect for a long time under high radiation or high temperature conditions.

[0004] Phase change materials (PCMs) have been used for heat storage and temperature equalization on the back side of photovoltaic (PV) modules due to their near-isothermal heat storage properties. However, existing PV thermal management systems combining conventional composite PCMs with water-cooled pipes primarily rely on PCM heat storage and a single water-cooling channel, failing to fully establish a spatial coupling relationship between near-panel liquid heat extraction, PCM layer temperature equalization and heat storage, and back-side air heat exchange. Furthermore, once the PCMs reach heat absorption saturation, their subsequent temperature regulation capability decreases. In addition, conventional PCMs suffer from low thermal conductivity, melt leakage, and poor cycle stability.

[0005] Therefore, there is an urgent need for a photovoltaic-thermal integrated system that can achieve efficient thermal management, multi-mode collaborative operation, and waste heat utilization. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a multi-mode dual-channel photovoltaic-thermal integrated system that integrates compounded biomass-based phase change materials. This system achieves efficient and uniform cooling and multi-mode waste heat recovery through a sandwich-style thermal management structure, effectively solving the problems of single heat exchange paths, decreased temperature regulation capability after phase change material saturation, and low waste heat utilization rate in existing technologies.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A multi-mode dual-channel photovoltaic-thermal integrated system includes a photovoltaic module unit, a composite phase change material layer disposed on the back surface of the photovoltaic module unit, a liquid heat exchange channel embedded in the composite phase change material layer, a heat dissipation fin plate disposed on the side of the composite phase change material layer away from the photovoltaic module unit, and a duct shell forming an airflow channel together with the heat dissipation fin plate; the composite phase change material layer is composed of a shaped composite phase change material body, and the liquid heat exchange channel is located on the side of the shaped composite phase change material body closer to the back surface of the photovoltaic module unit; the heat dissipation fin plate includes components related to the shaped composite phase change material layer. The back of the material body is attached to and encapsulated by a substrate and multiple fins extending into the airflow channel; the shaped composite phase change material body includes an organic phase change material with a phase change temperature of 30~40℃, expanded graphite and rice husk charcoal, with a mass ratio of 65~75:20~28:4~8; the liquid heat exchange channel and the airflow channel respectively form two independent heat exchange paths located inside and on the back side of the composite phase change material layer, which can operate independently or simultaneously under the action of the control unit to achieve four working modes: passive phase change heat storage, liquid heat extraction, air heat exchange regeneration, and liquid-air synergistic cooling.

[0008] Furthermore, the centerline of the liquid heat exchange channel is located in the half region of the back surface of the photovoltaic module unit in the thickness direction of the shaped composite phase change material body, so as to ensure that the high heat flux density heat from the photovoltaic module is preferentially removed.

[0009] Furthermore, the liquid heat exchange channel is a serpentine copper tube, which is uniformly arranged within the shaped composite phase change material body and is equipped with an inlet, an outlet, and a valve or pump for adjusting the liquid flow rate.

[0010] Furthermore, the heat dissipation fin plate is an aluminum fin plate, and its substrate serves as the back-side encapsulation cover plate of the shaped composite phase change material body. The plurality of fin teeth are arranged at intervals along the length direction of the substrate, and a heat dissipation gap communicating with the airflow channel is formed between adjacent fin teeth.

[0011] Furthermore, the expanded graphite forms a continuous thermally conductive framework in the shaped composite phase change material body, and the rice husk char forms a multi-level porous adsorption framework. The organic phase change material is confined within the composite pore network jointly formed by the continuous thermally conductive framework and the multi-level porous adsorption framework.

[0012] Furthermore, the organic phase change material is a paraffin-based solid-liquid phase change material with a phase change temperature of 30℃~40℃, and the mass ratio of the organic phase change material, expanded graphite and rice husk char is 70:24:6.

[0013] Furthermore, based on a total mass of 100 parts for the organic phase change material, expanded graphite, and rice husk char, the shaped composite phase change material body further includes 0.5 to 3 parts for flake boron nitride and 0.1 to 1 part for silane coupling agent; the flake boron nitride is dispersed along the substrate direction of the heat dissipation fin plate to enhance in-plane thermal conductivity; the silane coupling agent is located at the interface between the organic phase change material and the carbon-based or inorganic filler to improve cycle stability.

[0014] Furthermore, the air duct housing is composed of acrylic airflow channels. One end of the airflow channel is connected to the air supply device, and the other end serves as a hot air outlet. The airflow channel is used to output hot air during active air cooling in the daytime, and to forcibly discharge residual heat in the shaped composite phase change material body during low irradiation or shutdown phases, thereby realizing the rapid regeneration of the phase change material.

[0015] Furthermore, the system also includes a temperature detection unit and a control unit. The control unit automatically adjusts the liquid flow rate of the liquid heat exchange channel and the air volume of the airflow channel based on the temperature of the photovoltaic module unit, the temperature of the shaped composite phase change material body, the outlet water temperature, the outlet air temperature, the hot water demand signal, and the hot air demand signal, so as to match the thermal management requirements under different operating conditions.

[0016] A method for operating a multi-mode dual-channel photovoltaic-thermal integrated system includes: A. When the photovoltaic module unit (1) generates electricity from light and the temperature is below the first temperature threshold, the composite phase change material layer absorbs heat and dissipates heat naturally through the heat dissipation fin plate (5). B. When the temperature of the photovoltaic module unit (1) reaches or exceeds the first temperature threshold and there is a demand for hot water, coolant is introduced into the liquid heat exchange channel (3) and the outlet water temperature is controlled by adjusting the flow rate. C. When the temperature of the photovoltaic module unit (1) reaches or exceeds the first temperature threshold and there is a demand for hot air, airflow is introduced into the airflow channel (6) and the outlet temperature is controlled by adjusting the airflow. D. When the temperature of the photovoltaic module unit (1) reaches or exceeds the second temperature threshold or when there is both hot water demand and hot air demand, the liquid heat exchange channel (3) and the airflow channel (6) are opened simultaneously. E. Under low radiation, at night, or after the photovoltaic module unit (1) stops generating electricity, the airflow channel (6) is opened to regenerate the composite phase change material layer by air heat exchange.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention achieves spatial coupling and functional complementarity between liquid and air cooling media by constructing a sandwich-style dual-channel structure on the back of the photovoltaic module, consisting of "near-panel liquid heat exchange - composite phase change homogenization and heat storage - back-side fin air heat exchange". The liquid flow channel is close to the heat source, preferentially removing heat with high heat flux density; the phase change layer acts as a buffer and homogenizes the temperature; and the back-side fins provide additional heat dissipation area and air heat exchange path, effectively suppressing the temperature gradient caused by a single cooling method and improving the temperature uniformity of the photovoltaic module.

[0018] 2. This invention employs a composite system of "organic phase change material + expanded graphite + rice husk charcoal". The highly efficient thermally conductive network formed by expanded graphite significantly improves the overall thermal conductivity of the material, solving the problem of poor thermal conductivity in organic phase change materials; the hierarchical porous structure provided by biomass rice husk charcoal enhances the adsorption confinement capacity, effectively preventing the phase change material from melting and leaking, and improving cycle stability. The preferred formulation (70:24:6) and the addition of flake boron nitride and silane coupling agents further enhance in-plane thermal conductivity and interfacial compatibility.

[0019] 3. The system of this invention can intelligently switch between four modes—passive heat storage, liquid heat extraction, air heat exchange regeneration, and synergistic cooling—based on the temperature of the photovoltaic modules and the user's hot water and hot air needs. This not only achieves precise control of the photovoltaic module temperature but also enables the cascade utilization of waste heat (producing hot water and hot air), significantly improving the overall energy efficiency of the system. In particular, the "air heat exchange regeneration" mode can actively restore the heat storage capacity of the phase change material under low radiation or at night, ensuring the continuous and efficient operation of the system. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall structure of the multi-mode dual-channel photovoltaic-thermal integrated system provided in an embodiment of the present invention.

[0021] Figure 2 This is a schematic diagram of the side layered structure of the multi-mode dual-channel photovoltaic-thermal integrated system provided in an embodiment of the present invention.

[0022] Figure 3 This is a schematic diagram of the serpentine arrangement of liquid heat exchange channels in a composite phase change material layer, as provided in an embodiment of the present invention.

[0023] Figure 4 This is a differential calorimetry (DSC) test image of the PCM-A-35H solid-liquid phase change material used in the embodiments of the present invention.

[0024] Figure 5 The image shows a differential calorimetric scanning (DSC) test result of the PCM-A-35H-expanded graphite-rice husk carbon-shaped composite phase change material used in the embodiments of the present invention.

[0025] Figure 6This is a temperature curve of a single photovoltaic panel without cooling.

[0026] Figure 7 This is a temperature curve of the system in an embodiment of the present invention when active cooling is not used.

[0027] Figure 8 This is a temperature curve diagram of the system using active water cooling in an embodiment of the present invention.

[0028] Figure 9 This is a temperature curve diagram of the system using active air cooling in an embodiment of the present invention.

[0029] Figure 10 This is a temperature curve diagram of the system using water-air combined cooling in an embodiment of the present invention.

[0030] In the diagram: 1-Photovoltaic cell array, 2-Aluminum frame, 3-Water cooling pipe, 4-Composite phase change material layer, 5-Heat dissipation fin plate, 6-Air duct, 7-Acrylic airflow channel. Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0032] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "horizontal," "inner," "outer," and "one side," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, unless otherwise explicitly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0033] Example 1

[0034] Please see Figures 1 to 10This embodiment provides a multi-mode dual-channel photovoltaic-thermal integrated system, including a photovoltaic cell module 1, an aluminum frame 2, a water-cooling pipe 3, a composite phase change material layer 4, a heat dissipation fin plate 5, an air duct 6, and an acrylic airflow channel 7. The photovoltaic cell module 1 includes a light-receiving surface and a back-lighting surface. The composite phase change material layer 4 is attached to the back-lighting surface of the photovoltaic cell module 1. The water-cooling pipe 3 is embedded in the composite phase change material layer 4 and located on the side close to the back-lighting surface of the photovoltaic cell module 1. The heat dissipation fin plate 5 is disposed on the side of the composite phase change material layer 4 away from the photovoltaic cell module 1 and encapsulates the composite phase change material layer 4. The acrylic airflow channel 7 is fastened to the outside of the heat dissipation fin plate 5 and together with the heat dissipation fin plate 5 forms the air duct 6.

[0035] Thus, the heat from the back of the photovoltaic cell 1 is first transferred to the water cooling pipe 3 and the composite phase change material layer 4 on the near-panel side. The composite phase change material layer 4 stores and equalizes the heat, and the back side then exchanges heat with the air through the heat dissipation fin plate 5 and the air duct 6, forming a sandwich-type thermal management structure that couples the near-panel side liquid heat exchange, the composite phase change material layer for equalization and heat storage, and the back side fin air heat exchange.

[0036] In this embodiment, the composite phase change material layer 4 is a shaped composite phase change material consisting of organic phase change material, expanded graphite, and rice husk charcoal. Specifically, the organic phase change material is a paraffin-based solid-liquid phase change material with a phase change temperature of 30°C to 40°C, specifically PCM-A-35H. The expanded graphite has a leech-like morphology and an expansion ratio of approximately 400 times. The rice husk charcoal is a porous biomass charcoal material obtained from waste rice husks through drying, carbonization, grinding, and sieving. The expanded graphite forms a continuous thermally conductive framework, while the rice husk charcoal forms a hierarchical porous adsorption framework. Together, they confine the PCM-A-35H solid-liquid phase change material and reduce the risk of melt leakage.

[0037] In this embodiment, the mass ratio of PCM-A-35H solid-liquid phase change material, expanded graphite, and rice husk char is 70:24:6. The purity of PCM-A-35H solid-liquid phase change material is 99%. Figure 4 As shown, its phase transition temperature is 35℃ and its phase transition enthalpy is 234.2 J / g; the phase transition temperature of the composite phase change material layer 4 formed by pressing is still 35℃ and its phase transition enthalpy is 166.6 J / g, as... Figure 5 As shown.

[0038] As a preferred embodiment of the present invention, based on 100 parts by weight of PCM-A-35H solid-liquid phase change material, expanded graphite, and rice husk char, 0.5 to 3 parts of flake boron nitride and 0.1 to 1 part of silane coupling agent may be added to the composite phase change material layer 4. The flake boron nitride is dispersed along the substrate direction of the heat dissipation fin plate 5 to form an auxiliary in-plane heat conduction path; the silane coupling agent is located at the interface between the phase change material and the carbon-based or inorganic filler to improve the interface stability and anti-leakage ability during the cyclic melting-solidification process.

[0039] In this embodiment, the composite method for the composite phase change material layer 4 is as follows: treated rice husk charcoal and expanded graphite are weighed according to a predetermined ratio and physically stirred to ensure thorough mixing and form a uniform support matrix; the mixed support matrix is ​​preheated in a 65°C oven; solid PCM-A-35H is weighed according to a set ratio and heated in a 65°C constant temperature water bath until completely melted to obtain liquid PCM-A-35H; the preheated support matrix is ​​mixed with liquid PCM-A-35H and stirred for preliminary adsorption treatment; the mixture is then transferred to an electric vacuum drying oven, where a vacuum pressure of 64 kPa is applied at a constant temperature of 65°C and maintained for 2 hours to remove air from the pores of the support matrix and promote the full penetration of molten PCM-A-35H; subsequently, the vacuum is released and stirred, and the vacuuming and degassing process is repeated once to finally obtain the composite phase change material.

[0040] In this embodiment, the composite phase change material is filled and compacted into the aluminum frame 2, with a filling length of 770 mm and a width of 330 mm. The composite phase change material layer 4 is directly bonded to the back surface of the photovoltaic cell array 1, or thermally conductive grease or thermally conductive adhesive can be applied at the bonding interface to reduce contact thermal resistance.

[0041] In this embodiment, the water-cooling pipe 3 is a copper pipe with an inner diameter of 7.5 mm and an outer diameter of 8 mm. It is uniformly embedded in a serpentine pattern on the side of the composite phase change material layer 4 near the back surface of the photovoltaic cell module 1. The centerline of the water-cooling pipe 3 is located in the half area near the back surface of the photovoltaic cell module 1 in the thickness direction of the composite phase change material layer 4, so as to preferentially remove the high heat flux density heat from the photovoltaic module. The water-cooling pipe 3 is connected to the water supply system, and its inlet and outlet are equipped with pagoda connectors. It is connected to the water supply system through a flexible hose. A valve or water pump can be installed on the water inlet side to adjust the coolant flow rate.

[0042] In this embodiment, the heat dissipation fin plate 5 is an aluminum fin plate, including a substrate and multiple fin teeth. The substrate serves as the back-side encapsulation cover plate of the composite phase change material layer 4, and is attached to the back side of the composite phase change material layer 4; multiple fin teeth extend into the air duct 6, and heat dissipation gaps are formed between adjacent fin teeth. The base thickness of the heat dissipation fin plate 5 can be 8mm, the tooth thickness can be 3mm, and the height can be 50mm.

[0043] In this embodiment, the acrylic airflow channel 7 and the heat dissipation fin plate 5 together constitute the air duct 6. One end of the air duct 6 can be connected to the air supply system, and the other end serves as a hot air outlet. When the air supply system is running, the airflow passes through the air duct 6 and directly washes the fin teeth of the heat dissipation fin plate 5, carrying away the heat transferred from the composite phase change material layer 4 to the heat dissipation fin plate 5. The air duct 6 is used to output hot air during active air cooling in the daytime, and is used to forcibly remove residual heat in the composite phase change material layer 4 during low irradiation or shutdown phases, realizing rapid regeneration of the phase change material.

[0044] The system in this embodiment may include a temperature detection unit and a control unit. The temperature detection unit is used to detect the temperature of the photovoltaic cell array 1, the temperature of the composite phase change material layer 4, the outlet water temperature, and the outlet air temperature. The control unit automatically adjusts the liquid flow rate of the water cooling pipe 3 and the air volume of the air duct 6 according to the above temperature parameters and the hot water demand signal and hot air demand signal to match the thermal management requirements under different operating conditions. The temperature detection unit and the control unit can be implemented using existing temperature sensors, controllers, valves, water pumps, and fans, which are not shown in the accompanying drawings.

[0045] The usage method of the multi-mode dual-channel photovoltaic-thermal integrated system with integrated compound biomass-shaped phase change material provided in this embodiment is as follows: When there is sunlight, the photovoltaic cell module 1 receives solar radiation and converts it into electrical energy; when the temperature of the photovoltaic cell module 1 is below 40°C, the composite phase change material layer 4 absorbs the excess heat on the back of the photovoltaic cell module 1, the heat dissipation fin plate 5 dissipates heat naturally, the water cooling pipe 3 is closed, the air duct 6 does not provide active ventilation, and the system is in a passive phase change heat storage mode.

[0046] When the temperature of photovoltaic cell 1 is higher than 40°C and there is a demand for hot water, the inlet valve of the water cooling pipe 3 is opened, the air duct 6 does not perform active ventilation, and cold water enters the water cooling pipe 3 from the water supply system. During the flow process, the cold water preferentially carries away the heat on the side closest to the back of the photovoltaic cell 1, and the output water temperature is controlled by adjusting the flow rate of the coolant. The system is in liquid heat extraction mode.

[0047] When the temperature of the photovoltaic cell array 1 is higher than 40°C and there is a need for hot air, the water cooling pipe 3 is closed, the air duct 6 is actively ventilated, the airflow passes through the air duct 6 and washes the heat dissipation fin plate 5, taking away the heat transferred from the composite phase change material layer 4 to the heat dissipation fin plate 5, and the output airflow temperature is controlled by adjusting the air volume, and the system is in air heat exchange mode.

[0048] When the temperature of the photovoltaic cell array 1 rises further (reaching or exceeding the second temperature threshold), or when there is a demand for both hot water and hot air, the water cooling pipe 3 and the air duct 6 are turned on simultaneously. The water cooling pipe 3 removes heat from inside the composite phase change material layer 4, and the air duct 6 removes heat from the heat dissipation fin plate 5. Together, they reduce the temperature of the photovoltaic cell array 1 and improve the temperature uniformity of the plate surface. The system is in a liquid-air synergistic cooling mode.

[0049] When solar radiation decreases, the system shuts down at night, or the photovoltaic cell module 1 stops generating electricity, the control unit opens the air duct 6, allowing ambient air to carry away the residual heat in the composite phase change material layer 4 through the heat dissipation fin plate 5, promoting the PCM-A-35H to recover from a liquid or partially liquid state to a solid state, thereby restoring the heat storage and temperature regulation capability for the next working cycle, and the system is in air heat exchange regeneration mode.

[0050] In actual testing, a comparison between the technical solution in this embodiment and a single photovoltaic module revealed the following: The test experiment was conducted with an ambient temperature of 20℃, a total solar radiation intensity of 800W / m², an air supply volume of 75m³ / h, a circulating water temperature of 20℃, and a flow rate of 150ml / min. The average temperature was continuously measured for 240 minutes, during which: The peak surface temperature of photovoltaic panel 1 without any cooling method is approximately 71.5℃; The peak surface temperature of photovoltaic panel 1 when using a photovoltaic-thermal integrated system without any active cooling is approximately 71.5℃, but the heating process is significantly slowed down. The peak surface temperature of photovoltaic panel 1 when using a photovoltaic-thermal integrated system with single active water cooling is approximately 35.2℃; The peak surface temperature of photovoltaic panel 1 when using a photovoltaic-thermal integrated system and single active air cooling is approximately 61.2℃; The peak surface temperature of the photovoltaic panel 1 when using a photovoltaic-thermal integrated system and water-air co-cooling is approximately 34.2℃.

[0051] Based on the above data, it can be seen that this embodiment can reduce the peak temperature of the photovoltaic panel through the combined action of the composite phase change material layer 4, the water cooling pipe 3, the heat dissipation fin plate 5, and the air duct 6. At the same time, the water-air synergistic cooling mode can also output hot air while outputting hot water, and reduce the risk of thermal saturation of the composite phase change material layer 4 through back-side air heat exchange, which is beneficial to continuous operation stability and subsequent air heat exchange regeneration.

[0052] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A multi-mode dual-channel photovoltaic-thermal integrated system, characterized in that, The system includes a photovoltaic module unit (1), a composite phase change material layer disposed on the back surface of the photovoltaic module unit (1), a liquid heat exchange channel (3) embedded in the composite phase change material layer, a heat dissipation fin plate (5) disposed on the side of the composite phase change material layer away from the photovoltaic module unit (1), and a duct shell (7) that forms an airflow channel (6) together with the heat dissipation fin plate (5); the liquid heat exchange channel (3) is located on the side of the composite phase change material layer close to the back surface of the photovoltaic module unit (1); the heat dissipation fin plate (5) includes a back surface attached to and aligned with the back surface of the composite phase change material layer. The substrate for encapsulation and multiple fins extending into the airflow channel (6); the composite phase change material layer includes an organic phase change material with a phase change temperature of 30~40℃, expanded graphite and rice husk charcoal, with a mass ratio of 65~75:20~28:4~8; the liquid heat exchange channel (3) and the airflow channel (6) respectively form two independent heat exchange paths located inside and on the back side of the composite phase change material layer, and the two can operate independently or simultaneously under the action of the control unit to realize four working modes: passive phase change heat storage, liquid heat extraction, air heat exchange regeneration and liquid-air synergistic cooling.

2. The multi-mode dual-channel photovoltaic-thermal integrated system according to claim 1, characterized in that, The centerline of the liquid heat exchange channel (3) is located in half of the area of ​​the back surface of the photovoltaic module unit (1) in the thickness direction of the composite phase change material layer, so as to remove the high heat flux density heat from the photovoltaic module.

3. The multi-mode dual-channel photovoltaic-thermal integrated system according to claim 1, characterized in that, The liquid heat exchange channel (3) is a serpentine copper tube, which is uniformly arranged in the composite phase change material layer and is equipped with an inlet, an outlet, and a valve or pump for adjusting the liquid flow rate.

4. The multi-mode dual-channel photovoltaic-thermal integrated system according to claim 1, characterized in that, The heat dissipation fin plate (5) is an aluminum fin plate, and its substrate serves as the back-side encapsulation cover of the composite phase change material layer. The plurality of fin teeth are arranged at intervals along the length direction of the substrate, and a heat dissipation gap is formed between adjacent fin teeth that communicates with the airflow channel (6).

5. The multi-mode dual-channel photovoltaic-thermal integrated system according to claim 1, characterized in that, The expanded graphite forms a continuous thermally conductive framework in the composite phase change material layer, and the rice husk char forms a hierarchical porous adsorption framework. The organic phase change material is confined within the composite pore network jointly formed by the continuous thermally conductive framework and the hierarchical porous adsorption framework.

6. The multi-mode dual-channel photovoltaic-thermal integrated system according to claim 1, characterized in that, The organic phase change material is a paraffin-based solid-liquid phase change material with a phase change temperature of 30℃~40℃, and the mass ratio of the organic phase change material, expanded graphite and rice husk char is 70:24:

6.

7. The multi-mode dual-channel photovoltaic-thermal integrated system according to claim 1, characterized in that, Based on a total mass of 100 parts for the organic phase change material, expanded graphite, and rice husk char, the composite phase change material layer further includes 0.5 to 3 parts for flake boron nitride and 0.1 to 1 part for silane coupling agent; the flake boron nitride is dispersed along the substrate direction of the heat dissipation fin plate (5) to enhance in-plane thermal conductivity; the silane coupling agent is located at the interface between the organic phase change material and the carbon-based or inorganic filler to improve cycle stability.

8. The multi-mode dual-channel photovoltaic-thermal integrated system according to claim 1, characterized in that, The air duct housing (7) is made of acrylic airflow grooves. One end of the airflow channel (6) is connected to the air supply device, and the other end serves as a hot air outlet. The airflow channel (6) is used to output hot air during active air cooling in the daytime, and is used to forcibly discharge the residual heat in the composite phase change material layer during low irradiation or shutdown stages, so as to realize the rapid regeneration of the phase change material.

9. The multi-mode dual-channel photovoltaic-thermal integrated system according to claim 1, characterized in that, The system also includes a temperature detection unit and a control unit. The control unit automatically adjusts the liquid flow rate of the liquid heat exchange channel (3) and the air volume of the airflow channel (6) according to the temperature of the photovoltaic module unit (1), the temperature of the composite phase change material layer, the water outlet temperature, the air outlet temperature, the hot water demand signal and the hot air demand signal, so as to match the thermal management requirements under different working conditions.

10. A method for operating a multi-mode dual-channel photovoltaic-thermal integrated system as described in any one of claims 1 to 9, characterized in that, include: A. When the photovoltaic module unit (1) generates electricity from light and the temperature is below the first temperature threshold, the composite phase change material layer absorbs heat and dissipates heat naturally through the heat dissipation fin plate (5). B. When the temperature of the photovoltaic module unit (1) reaches or exceeds the first temperature threshold and there is a demand for hot water, coolant is introduced into the liquid heat exchange channel (3) and the outlet water temperature is controlled by adjusting the flow rate. C. When the temperature of the photovoltaic module unit (1) reaches or exceeds the first temperature threshold and there is a demand for hot air, airflow is introduced into the airflow channel (6) and the outlet temperature is controlled by adjusting the airflow. D. When the temperature of the photovoltaic module unit (1) reaches or exceeds the second temperature threshold or when there is both hot water demand and hot air demand, the liquid heat exchange channel (3) and the airflow channel (6) are opened simultaneously. E. Under low radiation, at night, or after the photovoltaic module unit (1) stops generating electricity, the airflow channel (6) is opened to regenerate the composite phase change material layer by air heat exchange.

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