A phase change thermal storage photovoltaic thermal collector

Abstract

This invention discloses a novel phase-change thermal storage photovoltaic (PV) collector, comprising a heat collection and transfer mechanism, a controller, and a hot water storage tank. The hot water storage tank is connected to a heat transfer tube within the heat transfer mechanism via a pipeline, on which a water pump is mounted. A temperature sensor is installed within the heat collection and transfer mechanism. Both the temperature sensor and the water pump are connected to the controller. The temperature sensor transmits collected data to the controller in real time, and the controller controls the operation of the water pump based on the data received from the temperature sensor. Beneficial effects: The novel phase-change thermal storage PV collector provided by this invention can effectively and rapidly reduce the temperature of photovoltaic cell modules, increasing their output power. It can also store and release heat in an orderly and efficient manner according to heat demand, synergistically improving the photoelectric and photothermal conversion efficiency, greatly enhancing the comprehensive utilization rate of solar energy, and promoting the efficient use of solar energy resources.

Description

Technical Field

[0001] This invention relates to a photovoltaic thermal collector, and more particularly to a phase change thermal storage photovoltaic thermal collector. Background Technology

[0002] Currently, photovoltaic cells can only convert a portion of solar energy into electrical energy, while the remaining energy is converted into heat energy, causing the photovoltaic cell temperature to rise and thus affecting the photovoltaic cell's photoelectric conversion output. Existing phase change thermal storage photovoltaic collectors suffer from problems such as low thermal conductivity of phase change materials, long heat storage and release cycles, and when the heat collected by the collector exceeds the heat stored by the phase change material, the temperature of the phase change material will rise sensibly, causing the photovoltaic cell temperature to rise. These problems directly lead to a reduction in the overall output performance of the device. Therefore, there is an urgent need to invent a phase change thermal storage photovoltaic collector to effectively solve the above problems. Summary of the Invention

[0003] The purpose of this invention is to solve the problem of low thermal conductivity of heat storage materials and the temperature rise of photovoltaic cells caused by the heat collection of heat being greater than that of phase change materials, and to provide a phase change heat storage photovoltaic thermal collector.

[0004] The phase change solar thermal storage photovoltaic collector provided by the present invention includes a heat collection and heat transfer mechanism, a controller, and a hot water storage tank. The hot water storage tank is connected to a heat transfer tube installed in the heat transfer mechanism via a pipeline. A water pump is installed on the connecting pipeline. A temperature sensor is installed in the heat collection and heat transfer mechanism. Both the temperature sensor and the water pump are connected to the controller. The temperature sensor can transmit the collected data to the controller in real time. The controller controls the operation of the water pump by receiving the data from the temperature sensor.

[0005] The heat collection and heat transfer mechanism includes a shell, a heat spreader plate, and heat transfer tubes, wherein the heat transfer tubes are assembled at the bottom of the shell, and the heat spreader plate is inserted into the inner cavity of the shell and the heat transfer tubes.

[0006] The top of the casing is sequentially equipped with a light-transmitting panel, photovoltaic cells, and a substrate. The light-transmitting panel consists of two layers of textured tempered glass, with a vacuum between them. The substrate has a three-layer structure, with the top layer being a transparent PET sheet to which the photovoltaic cells are bonded using EVA adhesive. The middle layer of the substrate is an absorption film, and the bottom layer is a high thermal conductivity metal layer. The absorption film in the middle layer is a selective absorption film made of reduced graphene oxide, with a solar absorptivity of 0.92 and a thermal emissivity of 4%. The bottom layer of the light-transmitting panel, textured tempered glass, is bonded to the transparent PET sheet using EVA adhesive. The inner cavity of the casing is connected to an exhaust pipe, with the exhaust port located at the top of the casing.

[0007] The heat spreader is arranged in several rows, and each row of heat spreaders is a one-piece molded structure. The heat spreader is a vacuum cavity with a capillary structure on the inner wall. The cavity is filled with working fluid. Each row of heat spreaders is divided into three working sections. The heat spreader attached to the bottom of the base plate at the top of the shell is the first working section. The section of the heat spreader located in the inner cavity of the shell after bending is the second working section. The heat spreader inserted into the heat transfer tube through the bottom of the shell and the side wall of the heat transfer tube is the third working section. Each row of heat spreaders assembled in the inner cavity of the shell is equipped with ribs between itself and the bottom of the shell.

[0008] The heat transfer tubes are elliptical metal tubes arranged in a serpentine pattern at the bottom of the shell. The inlet and outlet of the heat transfer tubes are connected to the hot water storage tank through pipelines.

[0009] The fins are metal plates with high thermal conductivity. The fins have circular holes of different radii, with the radius of the circular holes at the top of the fins being smaller than that at the bottom.

[0010] The inner cavity of the shell is filled with a phase change heat storage material, which is paraffin wax. The phase change temperature of the paraffin wax is around the average value of the ambient temperature. The temperature sensor is assembled in the phase change heat storage material.

[0011] An insulation layer is attached to the outside of the shell.

[0012] The controller, water pump, and temperature sensor mentioned above are all assemblies of existing equipment; therefore, their specific models and specifications are not detailed here.

[0013] Working principle of the invention:

[0014] The phase change solar thermal storage photovoltaic collector provided by this invention, when working, allows sunlight to pass through two layers of textured tempered glass on the top of the casing. Part of the sunlight is absorbed by the photovoltaic cells to generate electricity, while another part of the sunlight shines on the absorption film in the middle layer of the substrate through the transparent PET plate on the top layer of the substrate. Due to the low emissivity of the absorption film to the environment and the high absorptivity of the solar spectrum, this part of the sunlight is efficiently converted into heat energy. Furthermore, the absorption film has extremely low radiative heat transfer to the environment. The heat absorbed by the absorption film heats the PET plate and the substrate. This part of the heat energy is fully absorbed by the heat spreader at the bottom of the substrate. In addition, the space between the two layers of textured tempered glass on the top of the casing is a vacuum, which can effectively reduce the heat loss through this surface, greatly reduce the temperature of the photovoltaic cells, and improve the photoelectric conversion efficiency.

[0015] When sunlight shines on the substrate at the top of the shell, the generated heat energy is transferred to the first working section of the heat exchanger. The liquid working fluid between the capillary structures on the inner wall of the first working section of the heat exchanger in contact with the substrate absorbs the heat from the substrate and evaporates. The gaseous working fluid flows in the cavity of the heat exchanger under the drive of the working fluid vapor pressure. It is cooled and liquefied near the inner wall of the first working section of the heat exchanger in contact with the ribs and near the inner wall of the second working section. After liquefaction, the working fluid returns to the first working section of the heat exchanger under the action of capillary force. The ribs in contact with the first and second working sections of the heat exchanger transfer heat to the phase change heat storage material in the cavity of the shell.

[0016] Because the volume change of the phase change thermal storage material after solid-liquid and liquid-solid conversion will cause pressure changes in the internal space of the shell, the pressure is regulated by the exhaust pipe connected to the inner cavity of the shell to prevent the internal space pressure from being too low or too high.

[0017] To enhance the contact area between the first and second working sections of the heat exchanger and the phase change thermal storage material, several longitudinal ribs are arranged between the first and second working sections of the heat exchanger. The heat absorbed by the first and second working sections of the heat exchanger is transferred to the phase change thermal storage material through the ribs. After absorbing heat, the phase change thermal storage material completes a solid-liquid phase change and stores a large amount of heat. Due to the volume change of the phase change thermal storage material during solid-liquid and liquid-solid transitions, and the difference in heat transfer caused by the partial shading of sunlight on the shell surface by photovoltaic cells, the melting and solidification rates of the phase change thermal storage material in different rib compartments will vary. The circular holes on the ribs facilitate the flow of the liquid phase change thermal storage material. Since the liquid phase change thermal storage material has a high density and a higher liquid phase component in the lower space, the openings on the ribs are smaller on the upper side and larger on the lower side to facilitate the lateral flow of the liquid phase change thermal storage material.

[0018] The specific operating conditions are as follows:

[0019] Operating Condition 1: When the temperature sensor detects that the temperature of the phase change thermal storage material exceeds the phase change point, it indicates that the phase change thermal storage material has completely liquefied after absorbing heat. At this time, the controller commands the water pump to start, and the liquid working medium, such as water, in the heat transfer tube rushes the third working section of the heat exchange plate at high speed. At this time, the first working section of the heat exchange plate is the evaporation section, and the third working section is the condensation section. The heat collected by the photovoltaic collector unit is efficiently transferred to the liquid working medium in the heat transfer tube by the heat exchange plate. The photovoltaic cell can still maintain a low temperature, which can effectively avoid the problem that when the heat collected by the photovoltaic collector unit is greater than the heat stored by the phase change material, the heat of the photovoltaic cell itself cannot be transferred, and the temperature of the photovoltaic cell rises. Moreover, this heat can also be collected and utilized, maximizing the utilization of solar energy.

[0020] Operating Condition 2: When the user needs heat, the heat storage unit does not need to store heat. The water pump is started, and the liquid working medium, such as water, in the heat transfer tubes washes the third working section of the heat spreader at high speed. The heat absorbed by the photovoltaic collector is transferred to the first working section of the heat spreader, which is the evaporation section. The third working section of the heat spreader is the condensation section. The heat collected by the photovoltaic collector is efficiently transferred to the liquid in the heat transfer tubes by the heat spreader. The photovoltaic cells can be maintained at a lower temperature and maintain a high photoelectric conversion efficiency.

[0021] Operating Condition 3: When there is no sun at night and the user needs heat, the controller commands the water pump to start. The liquid working medium, such as water, in the heat transfer tube washes the third working section of the heat exchange plate at high speed. The second working section of the heat exchange plate in the shell is the evaporation section, and the third working section of the heat exchange plate is the condensation section. The heat stored in the heat storage unit is efficiently transferred to the liquid in the heat transfer tube by the heat exchange plate. When the temperature sensor detects that the temperature is lower than the phase change point of the phase change heat storage material, the phase change heat storage material changes from liquid to solid to release heat. At this time, the controller commands the water pump to be turned off.

[0022] The phase change heat storage material is paraffin wax, whose phase change point is similar to the average ambient temperature. This prevents the phase change point from being lower than the ambient temperature, thus preventing heat transfer from the environment to the material. If the phase change point is higher than the ambient temperature, the temperature of the photovoltaic cell will remain near the phase change point and higher than the ambient temperature. A higher photovoltaic cell temperature is not conducive to photoelectric conversion.

[0023] The beneficial effects of this invention are:

[0024] The phase change thermal storage photovoltaic thermal collector provided by this invention can effectively and quickly reduce the temperature of photovoltaic cell modules and increase their output power. It can also store and release heat in an orderly and efficient manner according to heat demand, thereby synergistically improving the photoelectric and photothermal conversion efficiency, greatly improving the comprehensive utilization rate of solar energy, and facilitating the efficient utilization of solar energy resources. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall structure of the photovoltaic thermal collector described in this invention.

[0026] Figure 2 This is a schematic diagram of the heat collection and heat transfer mechanism described in this invention.

[0027] Figure 3 This is a schematic diagram of the longitudinal cross-section of the photovoltaic thermal collector described in this invention.

[0028] Figure 4 This is a schematic diagram of the front cross-sectional structure of the photovoltaic thermal collector described in this invention.

[0029] The annotations in the image above are as follows:

[0030] 1. Heat collection and transfer mechanism; 2. Controller; 3. Hot water storage tank; 4. Heat transfer pipes

[0031] 5. Water pump; 6. Temperature sensor; 7. Housing; 8. Heat spreader; 10. Light-transmitting plate.

[0032] 11. Photovoltaic cell; 12. Substrate; 13. Exhaust pipe; 14. Fin; 15. Circular hole

[0033] 16. Insulation layer. Detailed Implementation

[0034] Please see Figures 1 to 4 As shown:

[0035] The phase change solar thermal storage photovoltaic collector provided by the present invention includes a heat collection and heat transfer mechanism 1, a controller 2, and a hot water storage tank 3. The hot water storage tank 3 is connected to a heat transfer tube 4 installed in the heat collection and heat transfer mechanism 1 through a pipeline. A water pump 5 is installed on the connecting pipeline. A temperature sensor 6 is installed in the heat collection and heat transfer mechanism 1. Both the temperature sensor 6 and the water pump 5 are connected to the controller 2. The temperature sensor 6 can transmit the collected data to the controller 2 in real time. The controller 2 controls the operation of the water pump 5 by receiving the data from the temperature sensor 6.

[0036] The heat collection and heat transfer mechanism 1 includes a shell 7, a heat spreader plate 8, and a heat transfer tube 4, wherein the heat transfer tube 4 is assembled at the bottom of the shell 7, and the heat spreader plate 8 is inserted into the inner cavity of the shell 7 and the heat transfer tube 4.

[0037] The top of the housing 7 is sequentially equipped with a light-transmitting plate 10, a photovoltaic cell 11, and a substrate 12. The light-transmitting plate 10 consists of two layers of textured tempered glass, with a vacuum between the two layers. The substrate 12 has a three-layer structure, with the top layer being a transparent PET sheet. The photovoltaic cell 11 is bonded to the PET sheet with EVA adhesive. The middle layer of the substrate 12 is an absorption film, and the bottom layer is a metal layer with high thermal conductivity. The absorption film in the middle layer of the substrate 12 is a selective absorption film made of reduced graphene oxide. The absorption film has a solar absorptivity of 0.92 and a thermal emissivity of 4%. The bottom layer of the light-transmitting plate 10 is bonded to the transparent PET sheet with EVA adhesive. The inner cavity of the housing 7 is connected to an exhaust pipe 13, with the exhaust port of the exhaust pipe 13 located at the upper end of the housing 7.

[0038] The heat spreader 8 is arranged in several rows, and each row of heat spreader 8 is an integrally formed structure. The heat spreader 8 is a vacuum cavity with a capillary structure on the inner wall. The cavity is filled with working fluid. Each row of heat spreader 8 is divided into three working sections. The heat spreader 8 attached to the bottom of the top substrate 12 of the shell 7 is the first working section. The section of the heat spreader 8 located in the inner cavity of the shell 7 after bending is the second working section of the heat spreader 8. The heat spreader 8 inserted into the heat transfer tube 4 through the bottom of the shell 7 and the side wall of the heat transfer tube 4 is the third working section of the heat spreader 8. Each row of heat spreader 8 assembled in the inner cavity of the shell 7 is equipped with ribs 14 between it and the bottom of the shell 7.

[0039] The heat transfer tube 4 is an elliptical metal tube, which is arranged in a serpentine pattern at the bottom of the shell 7. The inlet and outlet of the heat transfer tube 4 are connected to the hot water storage tank 3 through pipelines.

[0040] The fin 14 is a metal plate with high thermal conductivity. The fin 14 has circular holes 15 with different radii. The radius of the circular holes 15 in the upper part of the vertical direction of the fin 14 is smaller than that in the lower part.

[0041] The inner cavity of the housing 7 is filled with a phase change heat storage material, which is paraffin wax. The temperature sensor 6 is assembled in the phase change heat storage material.

[0042] An insulation layer 16 is attached to the outside of the shell 7.

[0043] The controller 2, water pump 5 and temperature sensor 6 mentioned above are all assemblies of existing equipment, therefore, their specific models and specifications are not described in detail.

[0044] Working principle of the invention:

[0045] When the phase change solar thermal storage photovoltaic collector provided by this invention is in operation, sunlight passes through the two layers of textured tempered glass plates on the top of the housing 7. Part of the sunlight is absorbed by the photovoltaic cells 11 to generate electrical energy, and another part of the sunlight is irradiated onto the absorption film in the middle layer of the substrate 12 through the transparent PET plate on the top layer of the substrate 12. Due to the low emissivity of the absorption film to the environment and the high absorptivity of the solar spectrum, this part of the sunlight is efficiently converted into heat energy. Moreover, the absorption film has extremely low radiative heat transfer to the environment. The heat absorbed by the absorption film heats the PET plate and the substrate 12. This part of the heat energy is fully absorbed by the heat spreader 8 at the bottom of the substrate 12. Furthermore, the space between the two layers of textured tempered glass on the top of the housing 7 is a vacuum, which can effectively reduce the heat loss through this surface, greatly reduce the temperature of the photovoltaic cells 11, and improve the photoelectric conversion efficiency.

[0046] When sunlight shines on the substrate 12 at the top of the housing 7, the generated heat energy is transferred to the first working section of the heat spreader 8. The liquid working fluid between the capillary structures on the inner wall of the heat spreader 8 absorbs the heat from the substrate 12 and evaporates. The gaseous working fluid flows in the cavity of the heat spreader 8 under the drive of the working fluid vapor pressure. It cools and liquefies near the inner wall of the second working section of the heat spreader 8. After liquefaction, the working fluid returns to the first working section of the heat spreader 8 under the action of capillary force. The ribs 14 that are in contact with the first and second working sections of the heat spreader 8 transfer heat to the phase change heat storage material in the cavity of the housing 7.

[0047] Because the volume change of the phase change thermal storage material after solid-liquid and liquid-solid conversion will cause pressure change in the internal space of the shell 7, in order to prevent the internal space pressure from being too low or too high, it is regulated by the exhaust pipe 13 connected to the inner cavity of the shell 7.

[0048] To enhance the contact area between the first and second working sections of the heat exchanger plate 8 and the phase change heat storage material, several longitudinal ribs 14 are arranged between the first and second working sections of the heat exchanger plate 8. The heat absorbed by the first and second working sections of the heat exchanger plate 8 is transferred to the phase change heat storage material through the ribs 14. After absorbing heat, the phase change heat storage material completes a solid-liquid phase change and stores a large amount of heat. Since the volume of the phase change heat storage material changes during solid-liquid and liquid-solid transitions, and the heat transfer will differ due to the partial shading of sunlight on the surface of the shell 7 by the photovoltaic cells 11, the melting and solidification rates of the phase change heat storage material in different rib 14 compartments will vary. The circular holes 15 provided on the ribs 14 facilitate the flow of the liquid phase change heat storage material. Since the liquid phase change heat storage material has a high density and more liquid phase component in the lower space, the openings on the ribs 14 are smaller on the upper side and larger on the lower side to facilitate the lateral flow of the liquid phase change heat storage material.

[0049] The specific operating conditions are as follows:

[0050] Operating Condition 1: When the temperature sensor 6 detects that the temperature of the phase change thermal storage material exceeds the phase change point, it indicates that the phase change thermal storage material has completely liquefied after absorbing heat. At this time, the controller 2 commands the water pump 5 to start. The liquid working fluid, such as water, in the heat transfer tube 4 washes the third working section of the heat spreader 8 at high speed, and the heat is transferred to the first working section of the heat spreader 8. At this time, the first working section of the heat spreader 8 is the evaporation section, and the third working section of the heat spreader 8 is the condensation section. The heat collected by the photovoltaic collector unit is efficiently transferred by the heat spreader 8 to the liquid in the heat transfer tube 4. The photovoltaic cell 11 can still maintain a lower temperature, which can effectively avoid the problem that when the heat collected by the photovoltaic collector unit is greater than the heat stored in the phase change material, the heat of the photovoltaic cell 11 itself cannot be transferred, and the temperature of the photovoltaic cell 11 rises. Moreover, this heat can also be collected and utilized, maximizing the utilization of solar energy.

[0051] Operating Condition 2: When the user needs heat, the heat storage unit does not need to store heat. The water pump 5 is started, and the liquid working medium, such as water, in the heat transfer tube 4 is flushed at high speed through the third working section of the heat spreader plate 8. The heat absorbed by the photovoltaic collector is transferred to the first working section of the heat spreader plate 8. The first working section of the heat spreader plate 8 is the evaporation section, and the third working section of the heat spreader plate 8 is the condensation section. The heat collected by the photovoltaic collector is efficiently transferred by the heat spreader plate 8 to the liquid in the heat transfer tube 4. The photovoltaic cell 11 can be maintained at a lower temperature and maintain a higher photoelectric conversion efficiency.

[0052] Operating Condition 3: When there is no sun at night and the user needs heat, the controller 2 commands the water pump 5 to start. The liquid working medium, such as water, in the heat transfer tube 4 washes the third working section of the heat spreader 8 at high speed. The second working section of the heat spreader 8 in the shell 7 is the evaporation section, and the third working section of the heat spreader 8 is the condensation section. The heat stored in the heat storage unit is efficiently transferred to the liquid in the heat transfer tube 4 by the heat spreader 8. When the temperature sensor 6 detects that the temperature is lower than the phase change point of the phase change heat storage material, the phase change heat storage material changes from liquid to solid to complete the heat release. At this time, the controller 2 commands the water pump 5 to be turned off.

Claims

1. A phase change thermal storage photovoltaic thermal collector, comprising a heat collection and heat transfer mechanism, a controller, and a hot water storage tank, wherein the hot water storage tank is connected to a heat transfer tube installed in the heat collection and heat transfer mechanism via a pipeline, a water pump is installed on the connecting pipeline, a temperature sensor is installed in the heat collection and heat transfer mechanism, and both the temperature sensor and the water pump are connected to the controller. The temperature sensor can transmit the collected data to the controller in real time, and the controller controls the operation of the water pump by receiving the data from the temperature sensor; characterized in that: The heat collection and transfer mechanism includes a shell, a heat spreader, and heat transfer tubes. The heat transfer tubes are assembled at the bottom of the shell, and the heat spreader is inserted into the inner cavity of the shell and the heat transfer tubes. Several rows of heat spreaders are arranged, each row being a one-piece molded structure. Each heat spreader is a vacuum cavity with a capillary structure on its inner wall, filled with a working fluid. Each row of heat spreaders is divided into three working sections: the heat spreader attached to the bottom of the top substrate of the shell is the first working section; the section of the heat spreader located within the inner cavity of the shell after bending is the second working section. The second working section consists of a heat spreader plate inserted into the heat transfer tubes through the bottom of the shell and the side wall of the heat transfer tubes. The third working section of the heat spreader plate consists of a rib installed between each row of heat spreaders in the shell cavity and the bottom of the shell. The ribs are metal plates with high thermal conductivity and have circular holes of different radii. The radius of the circular holes at the top of the vertical direction of the ribs is smaller than that at the bottom. The cavity of the shell is filled with a phase change heat storage material, which is paraffin wax. The temperature sensor is installed in the phase change heat storage material.

2. The phase change thermal storage photovoltaic thermal collector according to claim 1, characterized in that: The top of the housing is sequentially equipped with a light-transmitting plate, a photovoltaic cell, and a substrate. The light-transmitting plate consists of two layers of textured tempered glass, with a vacuum between them. The substrate has a three-layer structure, with the top layer being a transparent PET sheet to which the photovoltaic cell is bonded via EVA adhesive. The middle layer of the substrate is an absorption film, and the bottom layer is a high thermal conductivity metal layer. The absorption film in the middle layer is a selective absorption film made of reduced graphene oxide, with a solar absorptivity of 0.92 and a thermal emissivity of 4%. The bottom layer of the light-transmitting plate is bonded to the transparent PET sheet via EVA adhesive. The inner cavity of the housing is connected to an exhaust pipe, with the exhaust port located at the top of the housing.

3. The phase change thermal storage photovoltaic thermal collector according to claim 1, characterized in that: The heat transfer tube is an elliptical metal tube, which is arranged in a serpentine pattern at the bottom of the shell. The inlet and outlet of the heat transfer tube are connected to the hot water storage tank through pipelines.

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