A photovoltaic photo-thermal air collector

Abstract

The application is suitable for the technical field of solar power generation and heat collection, and provides a photovoltaic and photo-thermal air heat collector, which comprises a shell, a light-transmitting plate installed on the top of the shell, a space formed by the light-transmitting plate and the shell, a corrugated back plate fixedly installed on the bottom of the shell, photovoltaic cells, a substrate and 1 / 2 period ribs arranged in the space, the substrate is provided with multiple groups, each group of the substrate is fixedly connected with multiple 1 / 2 period ribs, the 1 / 2 period ribs are fixed on the crests of the corrugated back plate at the ends away from the substrate, multiple groups of the photovoltaic cells are attached to each substrate, and the two sides of the substrate are respectively an upper flow channel and a lower flow channel. Under the double effects of the upper and lower flow channels and the mutual cooperation of the 1 / 2 period ribs and the corrugated back plate in the lower flow channel, the convection heat exchange of air is greatly enhanced, the temperature of the photovoltaic cells is reduced, and the output of the whole heat collector is improved.

Description

Technical Field

[0001] This invention relates to the fields of solar power generation and heat collection technology, specifically a photovoltaic thermal air collector. Background Technology

[0002] Traditional flat-plate photovoltaic-thermal air collectors consist of a cover plate, photovoltaic cells, absorber plate, back plate, shell, and insulation layer (as shown in the attached image). Figure 1 As shown in the diagram, photovoltaic cells are laid flat on the heat absorber plate, and there is an air cooling channel between the heat absorber plate and the back plate. When the system is operating, the photovoltaic cells can only convert a small portion of the received solar energy into electrical energy, and the majority of the remaining energy is converted into heat energy. Due to the low heat capacity of air and the formation of an increasingly thick flow boundary layer on the inner wall of the cooling channel during the flow process, the convective heat transfer resistance is increased, which is not conducive to the convective heat transfer between the air and the heat absorber plate. This causes problems such as the photovoltaic cells themselves getting hotter and the air outlet temperature being low, which seriously affects the overall output performance of the collector.

[0003] Therefore, in view of the above situation, there is an urgent need to provide a photovoltaic thermal air collector to overcome the shortcomings of flat-plate photovoltaic thermal air collectors. Summary of the Invention

[0004] The purpose of this invention is to address the problems of low air heat capacity, high convective heat transfer resistance, and low air outlet temperature in traditional flat-plate photovoltaic thermal air collectors by redesigning their structure in conjunction with fluid flow characteristics and heat transfer mechanisms, and to provide a novel photovoltaic thermal air collector.

[0005] This invention is implemented as follows: a photovoltaic-thermal air collector, comprising:

[0006] The housing and the light-transmitting plate installed on the top of the housing form an airflow channel in the space enclosed by the light-transmitting plate and the housing.

[0007] A corrugated back plate, which is fixedly installed at the bottom of the housing;

[0008] The photovoltaic cells, substrate, and 1 / 2 period fins are disposed inside the air flow channel. The substrate is provided in multiple sets, and multiple 1 / 2 period fins are fixedly connected to each set of substrates. The ends of the multiple 1 / 2 period fins away from the substrate are fixed to the crests of the corrugated back plate. The multiple sets of photovoltaic cells are attached side by side to each substrate. The two sides of the substrate are the upper flow channel and the lower flow channel, respectively.

[0009] As a further aspect of the present invention: the light-transmitting plate comprises two layers of velvet tempered glass, and the two layers of velvet tempered glass are vacuum layers.

[0010] As a further aspect of the present invention: the substrate has a three-layer structure, with the top layer being a transparent PET board, the middle layer being an absorption film, and the bottom layer being a metal layer with high thermal conductivity.

[0011] As a further aspect of the present invention: the photovoltaic cell is bonded to the PET board with EVA adhesive, and the PET board and the metal layer are bonded together with EVA adhesive.

[0012] As a further aspect of the present invention: the absorption membrane is a selective absorption membrane, the material of the absorption membrane is reduced graphene oxide, the solar absorption rate of the absorption membrane is 0.92, and the thermal emissivity is 4%.

[0013] As a further aspect of the present invention: multiple sets of the substrates are arranged in a stepped shape in the airflow space, and the two ends of each substrate are fixedly connected to the two sides of the shell. There is a gap between adjacent substrates in the vertical direction, and the space formed by the substrates and the two sides of the shell is a microchannel.

[0014] As a further aspect of the present invention: the 1 / 2 cycle ribs are composed of metal plates with high thermal conductivity, the height of several rows of 1 / 2 cycle ribs increases sequentially, the starting end of each 1 / 2 cycle rib is connected to the end of the previous 1 / 2 cycle rib, the whole composed of multiple 1 / 2 cycle ribs presents a gradually expanding trend in the up, down and left and right, and the narrow slits formed by the staggered beginning and end of the adjacent 1 / 2 cycle ribs are microchannels II.

[0015] As a further aspect of the present invention: the adjacent 1 / 2 periodic ribs attached to the back of each of the substrates present a left-right symmetrical structure.

[0016] As a further aspect of the present invention: the corrugated back plate is a solid fixed structure, and one side of the corrugated back plate is corrugated, while the other side of the corrugated back plate is a flat surface, which is fixedly connected to the shell.

[0017] As a further aspect of the present invention, the two side plates and the bottom plate of the shell are filled with thermal insulation material.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] The photovoltaic-thermal air collector of this invention is theoretically sound and has significant effects. It thins the flow boundary layer on the upper surface of the photovoltaic cell and the back of the substrate, reduces the convective heat transfer resistance, greatly reduces the temperature of the photovoltaic cell itself, and synergistically improves the photoelectric conversion efficiency and photothermal conversion efficiency, thereby improving the overall output performance of the photovoltaic-thermal air collector and enhancing the utilization rate of solar energy. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a traditional flat-plate photovoltaic-thermal air collector.

[0021] Figure 2 This is a schematic diagram of the overall structure of a photovoltaic thermal air collector provided in an embodiment of the present invention.

[0022] Figure 3 This is a schematic diagram of the longitudinal cross-sectional structure of a photovoltaic thermal air collector provided in an embodiment of the present invention.

[0023] Figure 4 This is a schematic diagram of the front cross-sectional structure of a photovoltaic thermal air collector provided in an embodiment of the present invention.

[0024] Figure 5 This is a schematic diagram of the transverse cross-sectional structure of a photovoltaic thermal air collector provided in an embodiment of the present invention.

[0025] Figure 6 This is a schematic diagram of the structure of a 1 / 2 cycle fin in a photovoltaic-thermal air collector provided in an embodiment of the present invention.

[0026] In the attached diagram: 1-shell, 2-transparent plate, 3-photovoltaic cell, 4-substrate, 5-1 / 2 periodic ribs, 6-insulation material, 7-microchannel one, 8-vacuum layer, 9-microchannel two, 10-corrugated back plate. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0028] Please see Figure 2 and Figure 6 The present invention provides a photovoltaic thermal air collector, which includes:

[0029] The housing 1 and the light-transmitting plate 2 installed on the top of the housing 1 form an airflow channel in the space enclosed by the light-transmitting plate 2 and the housing 1;

[0030] Corrugated back plate 10, the corrugated back plate 10 is fixedly installed at the bottom of the housing 1;

[0031] The photovoltaic cells 3, substrate 4, and 1 / 2 periodic fins 5 are disposed inside the air flow channel. The substrate 4 is provided in multiple sets, and multiple 1 / 2 periodic fins 5 are fixedly connected to each set of substrate 4. The ends of the multiple 1 / 2 periodic fins 5 away from the substrate 4 are fixed to the crests of the corrugated back plate 10. Multiple sets of photovoltaic cells 3 are attached side by side to each substrate 4. The two sides of the substrate 4 are the upper flow channel and the lower flow channel, respectively.

[0032] In the embodiments of the present invention, the photovoltaic-thermal air collector theory is valid and the effect is significant. It thins the flow boundary layer on the upper surface of the photovoltaic cell 3 and the back of the substrate 4, reduces the convective heat transfer thermal resistance, greatly reduces the temperature of the photovoltaic cell 3 itself, and synergistically improves the photoelectric conversion efficiency and photothermal conversion efficiency, improves the overall output performance of the photovoltaic-thermal air collector, and can also improve the utilization rate of solar energy.

[0033] In one embodiment of the present invention, please refer to Figures 2-4 The light-transmitting plate 2 consists of two layers of velvet tempered glass, and the two layers of velvet tempered glass are a vacuum layer 8.

[0034] In one embodiment of the present invention, please refer to Figures 2-5 The substrate 4 has a three-layer structure, with the top layer being a transparent PET board, the middle layer being an absorption film, and the bottom layer being a metal layer with high thermal conductivity.

[0035] The photovoltaic cell 3 is bonded to the PET board with EVA adhesive, and the PET board is bonded to the metal layer with EVA adhesive.

[0036] The absorption membrane is a selective absorption membrane made of reduced graphene oxide. The membrane has a solar absorptivity of 0.92 and a thermal emissivity of 4%.

[0037] Multiple sets of substrates 4 are arranged in a stepped shape in the airflow space, and the two ends of each substrate 4 are fixedly connected to the two sides of the housing 1. There is a gap between adjacent substrates 4 in the vertical direction. The space formed by the substrates 4 and the two sides of the housing 1 is a microchannel 7.

[0038] In this embodiment, adjacent substrates 4 are spaced a certain distance apart in the vertical direction (with a gap);

[0039] In one embodiment of the present invention, please refer to Figures 2-4 as well as Figure 6 The 1 / 2 cycle rib 5 is composed of a metal plate with high thermal conductivity. The height of several rows of 1 / 2 cycle ribs 5 increases sequentially. The starting end of each 1 / 2 cycle rib 5 is connected to the end of the previous 1 / 2 cycle rib 5. The whole composed of multiple 1 / 2 cycle ribs presents a trend of gradually expanding up, down and left and right.

[0040] The adjacent half-cycle ribs 5 attached to the back of each substrate 4 have a left-right symmetrical structure.

[0041] In this embodiment, the 1 / 2-cycle ribs 5 are composed of metal plates with high thermal conductivity and are arranged in several rows. Each row has multiple 1 / 2-cycle ribs 5, and the height of the 1 / 2-cycle ribs 5 in the rear row is large. When arranged longitudinally, the upper end of each 1 / 2-cycle rib 5 is attached to the back of a substrate 4, and the middle of the other end abuts the crest of the corrugated back plate 10. The starting end of each 1 / 2-cycle rib 5 is connected to the end of the previous 1 / 2-cycle rib 5 at the microchannel 7, but is offset laterally by a certain distance, so that the whole composed of multiple 1 / 2-cycle ribs 5 presents a gradually expanding trend in the top, bottom and left and right. The unclosed space surrounded by the front and rear 1 / 2-cycle ribs 5 and the substrate 4 is the microchannel 9, which is on the same cross section as the microchannel 7. When arranged laterally, the adjacent 1 / 2-cycle ribs 5 attached to the back of each substrate 4 present a left-right symmetrical structure.

[0042] In one embodiment of the present invention, please refer to Figure 2 and Figure 3 The corrugated back plate 10 is a solid fixed structure, with one side of the corrugated back plate 10 being corrugated and the other side being a flat surface, which is fixedly connected to the housing 1.

[0043] In this embodiment, the material of the corrugated back plate 10 can be the same as that of the shell 1. It is a solid material and is fixedly connected to the shell 1, which can increase the thermal resistance of the bottom of the shell 1 and effectively reduce the heat loss through this surface.

[0044] In one embodiment of the present invention, please refer to Figure 2 The two side plates and the bottom plate of the shell 1 are filled with thermal insulation material 6.

[0045] In summary, the working principle of this invention is as follows:

[0046] During operation, sunlight passes through the two layers of textured tempered glass on the top of the housing 1. Part of the sunlight is absorbed by the photovoltaic cells 3 on the substrate 4 to generate electricity. Another part of the sunlight shines on the absorption film in the middle layer of the substrate 4 through the transparent PET plate on the top layer of the substrate 4. 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, the substrate 4 and the 1 / 2 periodic ribs 5. This part of the heat energy is fully absorbed by the air on the upper side of the photovoltaic cells 3 and the lower side of the substrate 4. Furthermore, the space between the two layers of textured tempered glass on the top of the housing 1 is a vacuum, which can effectively reduce the heat loss through this surface, greatly reduce the temperature of the photovoltaic cells 3, and improve the photoelectric conversion efficiency.

[0047] When air flows in the upper channel, the viscosity of the air will brake the air flow, that is, the air will form a flow boundary layer on the upper surface of the photovoltaic cell 3. According to Prandtl's boundary layer theory, the thickness of the boundary layer will gradually increase along the flow direction, and a large velocity gradient and temperature gradient will be generated inside the boundary layer. This will increase the convective heat transfer resistance. Since the substrate 4 is arranged in a stepped shape in this invention, after the flow boundary layer of the air thickens to a certain extent, it will be interrupted and split at the microchannel 7. A small part of the air will enter the lower channel through the microchannel 7, reform the boundary layer on the back of the substrate 4 and increase the air flow in the lower channel. It will also affect the back step flow formed by the air in the lower channel during the flow on the back of the substrate 4, that is, it will hinder the formation of the velocity stagnation area in the inner corner of the back step flow. The remaining part of the air will reform the boundary layer on the surface of the photovoltaic cell 3 of the next step, and flow back and forth. The thickness of the flow boundary layer on the surface of the photovoltaic cell 3 is always relatively thin, which enhances the heat exchange between the photovoltaic cell 3 and the air in the upper channel, reduces the temperature of the photovoltaic cell 3 itself, and improves the overall output performance of the collector.

[0048] The corrugated back plate 10 is a solid material with one side corrugated and the other side flat and fixed to the shell 1. The material can be the same as that of the shell 1. Using a solid material and being fixed to the shell 1 can increase the thermal resistance of the bottom of the shell 1 and effectively reduce the heat loss through this surface.

[0049] When air flows in the lower channel, viewed from the overall transverse section, the entire structure composed of discontinuous 1 / 2-period ribs 5 exhibits a gradually expanding trend in all directions. Therefore, the shape of the channels divided by the discontinuous 1 / 2-period ribs 5 shows a gradually contracting trend. Furthermore, since each 1 / 2-period rib 5 abuts against the corrugated back plate 10 at the middle of the 1 / 2-period rib 5, and in the transverse arrangement, the adjacent 1 / 2-period ribs 5 attached to the back of each substrate 4 exhibit a left-right symmetrical structure, that is, viewed locally from the transverse section, as air rises from the trough to the crest of the corrugated back plate 10, adjacent segmented channels either show a gradually contracting trend or a gradually expanding trend. Therefore, although adjacent segmented channels both exhibit a gradually contracting trend overall, viewed locally from the same transverse section, their airflow channel forms are different, resulting in different airflow patterns, as detailed below:

[0050] Form 1: If the two sides of the segmented flow channel are 1 / 2 cycle fins 5 with a gradually decreasing trend, the flow cross-sectional area gradually decreases during airflow, which on the one hand leads to an increase in velocity, thins the flow boundary layer on the back of the substrate 4 in this area, reduces the convective heat transfer resistance and promotes convective heat transfer. On the other hand, due to the mutual compression of the air inside, a flow split is generated, which flows through the microchannel 2 9 to the adjacent segmented flow channel and regenerates the flow boundary layer on the back of the next 1 / 2 cycle fin 5. Moreover, during the air shrinkage process, it will directly scour the front part of the 1 / 2 cycle fin 5, and the heat of the substrate 4 is guided to the 1 / 2 cycle fin 5 by heat conduction and is fully carried away by the air, further improving the convective heat transfer between the air and the fins.

[0051] Form 2: If the two sides of the segmented flow channel are 1 / 2 periodic ribs 5 with a gradually expanding trend, the flow cross-sectional area during airflow gradually increases and the flow velocity decreases. However, when the flow cross-sectional area of ​​the segmented flow channel increases to the maximum, the flow cross-section at this time is on the same plane as the cross-section of microchannel 1 7 and microchannel 2 9. Part of the air from the upper flow channel is diverted through microchannel 1 7 and part of the air from the adjacent two-sided segmented flow channels is diverted through microchannel 2 9, which increases the airflow of this segmented flow channel and increases the mixing of air inside the adjacent segmented flow channels. After that, as the flow cross-sectional area of ​​the segmented flow channel gradually decreases from the maximum, the flow will be consistent with that described in Form 1.

[0052] The novel photovoltaic-thermal air collector, under the dual action of the upper and lower flow channels, and the combined action of the 1 / 2 cycle fins 5 and the corrugated back plate 10 in the lower flow channel, greatly enhances the convective heat transfer of the air, significantly reduces the temperature of the photovoltaic cell 3 itself, and improves the photoelectric conversion efficiency and photothermal conversion efficiency in a synergistic manner, thereby improving the overall output performance of the collector.

[0053] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A photovoltaic-thermal air collector, comprising a housing and a light-transmitting plate mounted on the top of the housing, wherein the space enclosed by the light-transmitting plate and the housing forms an airflow channel, characterized in that, Also includes: A corrugated back plate, which is fixedly installed at the bottom of the housing; The photovoltaic cells, substrate, and 1 / 2 period fins are disposed inside the air flow channel. The substrate is provided in multiple sets, and multiple 1 / 2 period fins are fixedly connected to each set of substrates. The ends of the multiple 1 / 2 period fins away from the substrate are fixed to the crests of the corrugated back plate. The multiple sets of photovoltaic cells are attached side by side to each substrate. The two sides of the substrate are the upper flow channel and the lower flow channel, respectively. Multiple sets of substrates are arranged in a stepped shape in the airflow space, and the two ends of each substrate are fixedly connected to the two sides of the shell. There is a gap between adjacent substrates in the vertical direction. The space formed by the substrates and the two sides of the shell is a microchannel. The 1 / 2 cycle fins are composed of metal plates with high thermal conductivity. The height of several rows of 1 / 2 cycle fins increases sequentially. The starting end of each 1 / 2 cycle fin is connected to the end of the previous 1 / 2 cycle fin. The whole composed of multiple 1 / 2 cycle fins presents a trend of gradually expanding up, down, left and right.

2. The photovoltaic-thermal air collector according to claim 1, characterized in that, The light-transmitting panel consists of two layers of textured tempered glass, and the two layers of textured tempered glass are vacuum layers.

3. The photovoltaic-thermal air collector according to claim 1, characterized in that, The substrate has a three-layer structure, with the top layer being a transparent PET sheet, the middle layer being an absorption film, and the bottom layer being a metal layer with high thermal conductivity.

4. The photovoltaic-thermal air collector according to claim 3, characterized in that, The photovoltaic cells are bonded to the PET board with EVA adhesive, and the PET board is bonded to the metal layer with EVA adhesive.

5. The photovoltaic-thermal air collector according to claim 3, characterized in that, The absorption membrane is a selective absorption membrane made of reduced graphene oxide. The absorption membrane has a solar absorptivity of 0.92 and a thermal emissivity of 4%.

6. The photovoltaic-thermal air collector according to claim 1, characterized in that, The adjacent half-cycle ribs attached to the back of each substrate have a left-right symmetrical structure.

7. The photovoltaic-thermal air collector according to claim 1, characterized in that, The corrugated back plate is a solid fixed structure, with one side of the corrugated back plate being corrugated and the other side being a flat surface, which is fixedly connected to the shell.

8. The photovoltaic thermal air collector according to claim 1, characterized in that, The two side plates and the bottom plate of the shell are filled with thermal insulation material.

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