Zero-energy-consumption real-time photovoltaic panel passive cooling device

Abstract

The invention discloses a zero-energy-consumption real-time photovoltaic panel passive cooling device, and belongs to the technical field of photovoltaic panel cooling. Zero-carbon operation of the system is achieved while real-time temperature drop of the photovoltaic panel is obtained, water vapor is cooled in time through the micro-channel-Janus micro-membrane, and the operation performance of the photovoltaic panel under various complex climate environment conditions is improved. Comprising a solar evaporative cooling system, a condensation circulating device and a water collecting device, the water collecting device and the condensation circulating device are connected through preset room-temperature cooling water, the cooling water serves as a cold source to promote condensation of water vapor in the condensation system, and waste heat of the system is collected to promote evaporation to provide a humidity environment for a hygroscopic medium. Water on the lower layer is evaporated under the combined action of waste heat of the photovoltaic panel and steam condensation heat release, and formed steam is diffused in the system so that a high-humidity environment can be formed. According to the method for forming high humidity by utilizing waste heat of the photovoltaic panel and steam condensation heat dissipation to evaporate water, the defect that the adsorption capacity of a hygroscopic medium is low under low humidity is fundamentally avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of photovoltaic panel cooling, and in particular relates to a zero-energy-consumption real-time photovoltaic panel passive cooling device. Background Art

[0002] Due to the limited band gap of silicon-based semiconductor materials, only a small portion of photons are absorbed to achieve photoelectric conversion, and a considerable portion of the remaining photons are converted into waste heat on the surface, so that photovoltaic modules can only convert less than 20% of the energy in solar radiation into electrical energy, and the rest is converted into heat, causing the temperature of the photovoltaic panels to rise. High temperature will have an adverse effect on photovoltaic modules and may even damage the internal structure of the modules. Such temperature effect has become an important factor restricting the efficiency of photovoltaic power generation. High-efficiency photovoltaic panel water spray cooling technology is difficult to apply in some areas. Therefore, it is urgent to develop a refrigeration technology that is efficient, energy-saving, and independent of external power supply and liquid water resources.

[0003] In order to achieve the purpose of cooling the photovoltaic panel, a circulating refrigeration system that pumps cooling water is usually used. For example, the existing invention patent with publication number CN220528008U discloses a photovoltaic power generation radiator, which cools the photovoltaic panel by setting a cooling water tank, a circulating cooling pipe, a semiconductor refrigeration sheet and a water pump, and further cools the photovoltaic panel by using a heat conducting plate, a heat dissipation fin and a fan, thereby improving the performance and service life of the photovoltaic panel. Another example is the invention patent with publication number CN219577002U, in which the cooling water is in full contact with the back of the photovoltaic panel, so that the heat of the photovoltaic panel is taken away in time, and the photovoltaic panel is effectively cooled.

[0004] The above cooling strategies all require a large amount of cooling water during application. Although the water cooling process accompanied by the evaporation effect can enable the photovoltaic panels to obtain a significant cooling effect, water resources cannot be completely recycled and additional energy is required to drive the pumping device. Summary of the invention

[0005] The purpose of the present invention is to provide a real-time photovoltaic panel passive cooling device with zero energy consumption, which can achieve zero-carbon operation of the system while obtaining real-time temperature drop of the photovoltaic panel, and timely cool water vapor through microchannel-Janus microfilm to improve the operation performance of photovoltaic panels under various complex climate conditions. It is used to solve the stability and drinking water safety problems of photovoltaic power generation in remote environments, energy-deficient and water-scarce areas and outdoor working environments.

[0006] The technical solution adopted by the present invention is:

[0007] A zero-energy real-time photovoltaic panel passive cooling device comprises a solar evaporative cooling system, a condensing circulation device and a water collecting device; the solar evaporative cooling system is arranged above the condensing circulation device, and the condensing circulation device and the water collecting device are connected through room temperature cooling water pre-arranged in the water collecting device.

[0008] Compared with the prior art, the present invention has the following beneficial effects:

[0009] 1. The present invention prepares a back-mounted lithium-rich high-efficiency hygroscopic medium to enhance the adsorption and analysis of moisture in the atmosphere. The internal water evaporates rapidly at high temperature of the photovoltaic panel to dissipate the waste heat generated by carrier transport; thereby obtaining a solar photovoltaic panel passive cooling device with efficient operation, solving the adverse effects of high temperature on the power generation efficiency of photovoltaic modules, and promoting the development of green and sustainable solar photovoltaic energy.

[0010] 2. A condensation water layer is provided in the water collecting device of the present invention. The water vapor generated by the evaporative cooling system diffuses downward to the condensation circulation device. There is a temperature difference between the evaporated water vapor and the lower cooling water, and condensation occurs. The condensation device collects the evaporated water inside the hygroscopic medium and recycles it. The present invention gets rid of the restrictions on the acquisition of liquid water resources, has no CO2 emissions, alleviates the greenhouse effect, and provides a promising method for efficient and sustainable power generation of photovoltaic panels.

[0011] 3. The present invention combines a microchannel with super-hydrophobic properties with a wettability gradient microfilm (Janus microfilm) from super-hydrophobicity to hydrophilicity, and uses the Janus microfilm to induce the directional migration of droplets from the super-hydrophobic surface to the hydrophilic surface, thereby achieving rapid combination with the unformed water column in the super-hydrophobic microchannel, timely refreshing the attachment surface of the micro-droplets, and the condensed water droplets are easy to slide off due to the properties of the super-hydrophobic surface, reducing the obstruction of heat transfer. The droplets nucleate, grow and coalesce to form a liquid column in the microchannel. When each liquid column grows and contacts the hydrophobic net, the condensed droplets on the net membrane are removed, thereby separating the vapor flow and the liquid flow, resulting in higher heat transfer.

[0012] 4. In the present invention, the water collection device and the condensation circulation device are connected by pre-set room temperature cooling water. The cooling water acts as a cold source to promote the condensation of water vapor in the condensation system, and the waste heat of the collection system promotes evaporation to provide a humidity environment for the hygroscopic medium. The lower layer of moisture is evaporated under the combined action of the waste heat of the photovoltaic panel and the heat released by steam condensation, and the formed water vapor diffuses inside the system to form a high humidity environment. The method of using the waste heat of the photovoltaic panel and the heat dissipation of steam condensation to evaporate moisture and thus form a high humidity is named environmental passive humidification method. This method fundamentally avoids the weakness of low adsorption capacity of hygroscopic media under low humidity.

[0013] 5. Create a high humidity environment to promote the continuous moisture absorption of the hygroscopic medium, which further extends the cooling of the photovoltaic panel. During the operation of the solar panel, this design realizes the dynamic cycle of adsorption and desorption of the hygroscopic medium through the high humidity environment formed in the system and its own waste heat, thereby achieving a continuous temperature drop of the photovoltaic panel.

[0014] 6. When it is dark (at night or on a cloudy day), the photovoltaic panel enters a dormant state. At this time, the adsorption capacity of the hygroscopic medium exceeds the desorption capacity, and it continues to absorb moisture in the high humidity environment provided by the system until it is under light conditions. The system-based real-time photovoltaic panel cooling enters a new cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0016] Figure 2 is a top view of the present invention;

[0017] Figure 3 It is a schematic diagram of the structure of the solar evaporative cooling system of the present invention;

[0018] Figure 4 It is a schematic diagram of the side wall structure of the condensation circulation device of the present invention;

[0019] Figure 5 It is a schematic diagram of the working principle of the Janus micromembrane of the present invention;

[0020] Figure 6 It is a schematic diagram of the condensation behavior of water vapor on the side wall of the condensation cycle device;

[0021] Figure 7 It is a schematic diagram of the working principle of the present invention;

[0022] Figure 8 is a schematic diagram of the hygroscopic medium of the present invention;

[0023] Fig. 9 This is a diagram showing the cooling effect of the hygroscopic medium of the present invention on the surface of a photovoltaic panel;

[0024] Fig.10 It is a graph showing the improvement of the actual operating voltage of the photovoltaic panel under illumination conditions by the hygroscopic medium of the present invention;

[0025] Fig.11 This is a diagram showing the cooling effect of hygroscopic media on the back panel of a photovoltaic panel;

[0026] Among them: 1. Photovoltaic panel; 2. Silicone gasket; 3. Hygroscopic medium; 4. Condensation circulation device; 5. Water collection device; 6. Support net; 7. Microchannel; 8. Janus micromembrane; 9. Droplet; 10. Liquid column; 11. Water vapor; 12. Lithium chloride. DETAILED DESCRIPTION

[0027] In order to better understand the purpose, structure and function of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings.

[0028] The present invention is a composite cycle cooling technology that uses the waste heat of photovoltaic panels to drive evaporative cooling, microchannel cooling and passive humidification. The evaporative cooling strategy, atmospheric water collection technology and microchannel cooling technology are combined, and the evaporative cooling structure and the water collection device for microchannel cooling are integrated and optimized. The internal water relies on the high temperature of the photovoltaic panel to evaporate quickly to dissipate the waste heat generated by carrier transport, realizing "zero" carbon photovoltaic panel cooling and real-time operation.

[0029] The hygroscopic medium 3 is attached to the back of the photovoltaic panel 1. The heat generated by the photovoltaic panel 1 when working is diffused by the evaporation of water in the hygroscopic medium 3 to form water vapor. The heat migration promotes the cooling of the photovoltaic panel 1. The water vapor diffuses downward into the condensation circulation device 4. The super-hydrophobic microchannel-Janus microfilm on the wall of the condensation circulation device 4 condenses the water vapor in time. The condensed water droplets are easy to slide due to the properties of the super-hydrophobic surface, reducing the obstruction of heat transfer. The hygroscopic medium 3 uses the heat generated by the photovoltaic panel 1 when working to drive the evaporation of the bottom layer of the condensation circulation device 4, thereby providing a high humidity environment for its adsorption. At the same time, the desorption is driven by the heat of the photovoltaic panel 1 to achieve the purpose of cooling the photovoltaic panel 1. The hygroscopic medium 3 in the system simultaneously adsorbs and desorbs, so that the water inside it reaches a dynamic equilibrium state, ensuring the continuous water storage and cooling capacity of the hygroscopic medium 3, and extending the passive cooling time of the photovoltaic panel 1. At night, the adsorption capacity of the hygroscopic medium 3 exceeds the desorption capacity, and the system continues to absorb moisture in the high humidity environment until the next day, when the photovoltaic panel 1 of the system is cooled in real time and enters a new cycle.

[0030] The evaporative cooling system, the condensation circulation device 4 and the water collection device are integrated to achieve "zero" carbon photovoltaic panel cooling and real-time operation.

[0031] The evaporative cooling system is obtained by integrating the hygroscopic medium 3 on the back plate of the photovoltaic panel 1. The evaporative cooling system is divided into the photovoltaic panel 1 power generation layer and the hygroscopic medium 3 cooling layer. The solar radiation reaching the photovoltaic panel 1 is partially converted into electrical energy and partially converted into heat to increase the temperature of the solar panel. The converted heat is then transferred downward to the hygroscopic medium 3 cooling layer to drive the evaporation of water and realize evaporative passive cooling of the photovoltaic panel 1.

[0032] The condensation circulation device 4 is made of a super-hydrophobic microchannel 8 combined with a super-hydrophobic to hydrophilic wettability gradient microfilm (Janus microfilm 8). The heat of the photovoltaic panel 1 is released in the form of water vapor in the condensation circulation device 4 and condensed in the system device.

[0033] The water collecting device 5 is specially made of acrylic plate. The water condensed in the condensation circulation device 4 is collected in the water collecting device, and the heat is transferred to the condensation circulation device 4 through the condensation of water vapor.

[0034] Reference Figure 1 to Figure 3 As shown, a zero-energy real-time photovoltaic panel passive cooling device of the present invention includes a solar evaporative cooling system ( Figure 3 ), condensation circulation device 4, water collection device 5;

[0035] The solar photovoltaic panel 1 directly converts solar radiation energy into direct current to provide electricity to users, and the excess electricity is connected to the power grid, forming a zero-carbon emission, high-efficiency, and low-cost business model. The hygroscopic medium 3 absorbs water vapor from the condensation circulation device 4 and converts it into liquid water for storage. The heat generated during the operation of the solar photovoltaic panel 1 is transferred to the hygroscopic medium 3 through the back plate. The water stored in the hygroscopic medium 3 evaporates using this energy, and the water vapor takes away a large amount of evaporation latent heat and dissipates it in the environment through the trough cooling channel, thereby achieving cooling of the photovoltaic panel 1.

[0036] A condensation water layer is set in the water collection device 5, and the water vapor diffuses downward into the condensation circulation device 4. Due to the temperature difference between the upper and lower parts of the condensation circulation device 4, condensation occurs. The function of the condensation circulation device 4 is to collect the evaporated water in the hygroscopic medium 3 and recycle it. The water collection device 5 and the condensation circulation device 4 are connected by the pre-set room temperature cooling water. The cooling water has two functions: one is to act as a cold source to cool the high thermal conductivity copper condensation circulation device 4 and promote the condensation of water vapor in the condensation system; the other is to collect the system waste heat to promote evaporation and provide a humidity environment for the hygroscopic medium 3. The lower layer of water is evaporated under the combined action of the waste heat of the photovoltaic panel 1 and the heat released by the condensation of steam, and the formed water vapor diffuses inside the condensation circulation device 4 to form a high humidity environment. The formation of a high humidity environment can promote the moisture absorption of the hygroscopic medium 3 and provide further real-time cooling for the photovoltaic panel 1. The purpose of this design is to realize the adsorption and desorption cycle of the hygroscopic medium 3 through the high humidity environment formed in the condensation circulation device 4 and its own waste heat during the operation of the photovoltaic panel 1, thereby realizing the real-time passive cooling and temperature drop of the photovoltaic panel 1.

[0037] Figure 3 The design principle of the system for passively cooling photovoltaic panels using a hygroscopic medium 3 is demonstrated. The photovoltaic cooling system consists of a photovoltaic panel 1, a silicone gasket 2, a hygroscopic medium 3 and a support mesh 6. Figure 3As shown, relying on the viscosity of the hygroscopic medium, the hygroscopic medium 3 is attached to the back of the photovoltaic panel 1. The heat generated during the operation of the photovoltaic panel 1 is transferred to the hygroscopic medium 3 through the back plate. The water stored in the hygroscopic medium 3 evaporates using this energy, and the water vapor takes away a large amount of evaporation latent heat and dissipates in the condensation circulation device 4, thereby achieving the cooling of the photovoltaic panel 1. A flexible silicone gasket 2 is placed between the hygroscopic medium 3 and the photovoltaic panel 1 to prevent the water vapor generated by the evaporation of the hygroscopic medium 3 from escaping, thereby weakening the humidity in the cooling circulation system.

[0038] Adjust the evaporative cooling system according to the local latitude and longitude ( Figure 2 ) and the direct rays of sunlight to maximize the reception of solar radiation.

[0039] The hygroscopic medium 3 uses the hydration and deliquescence of lithium chloride 12 for adsorption.

[0040] When preparing the hygroscopic medium 3, a 0.4 g / mL LiCl solution is used and the proportion is made according to lithium chloride (LiCl, ≥99%).

[0041] A support net 6 is provided below the hygroscopic medium 3 and connected to the photovoltaic panel 1 to prevent the hygroscopic medium 3 from losing its viscosity during evaporation and separating from the photovoltaic panel to form a gap and fall off, thereby increasing heat transfer resistance.

[0042] Figure 4 The specific structure of the side of the copper condensation circulation device 4 is shown. The cold condensation circulation device 4 is an enclosed structure with upper and lower openings as a whole. The photovoltaic cooling system is fixed on the top of the cold condensation circulation device 4 by a bracket, or it can be arranged on the top of the condensation circulation device 4 by other supporting methods. The side wall of the cold condensation circulation device 4 is modified, and the structure of the microchannel 7 with super-hydrophobic properties is adopted on the side wall of the cold condensation circulation device 4. The outer surface of the microchannel 7 is covered with a wettability gradient microfilm Janus microfilm 8 from super-hydrophobic to hydrophilic. The microchannel 7 with super-hydrophobic properties is combined with a wettability gradient microfilm (Janus microfilm 8) from super-hydrophobic to hydrophilic. The Janus microfilm 8 is close to the microchannel 7 on one side and the super-hydrophobic surface on the other side. The Janus microfilm 8 is used to induce the droplets to migrate from the super-hydrophobic surface to the hydrophilic surface, so as to achieve rapid combination with the microgroove water column 10, and timely refresh the attachment surface of the micro-droplets 9, so that the unformed water column in the microchannel 7 is quickly combined with the droplets on the microfilm 8.

[0043] The super-hydrophobic microchannel 7 has a width of 400 μm and a height of 200 μm.

[0044] Janus Microfilm 8 uses a 300 mesh copper screen.

[0045] The method for making the super-hydrophobic microchannel 7 is as follows: first, the microchannel 7 is continuously ultrasonically washed with acetone, anhydrous ethanol and deionized water, and the microchannel 7 is immersed in an ammonia solution. After a period of reaction (20 minutes), the copper surface is covered with Cu(OH)2 nanobelts. After ammonia corrosion, the sample is rinsed with deionized water and dried with a nitrogen stream. Then, the super-hydrophilic microchannel 7 is immersed in an ethanol solution of 2mM n-octadecanethiol (ODT) and heated in a constant temperature water bath at 70°C for 1 hour. Then, anhydrous ethanol is used to clean the sample surface to remove the unreacted n-octadecanethiol solution, and finally a microchannel 7 with super-hydrophobic properties is generated.

[0046] The ammonia solution was prepared by reacting 1 M NaOH and 0.05 M (NH4)2S2O8 in 100 mL of deionized water.

[0047] Figure 5 The working principle of the Janus micromembrane 8 is demonstrated. One side is a hydrophilic surface, and the other side is a superhydrophobic surface. Its asymmetric wettability enables unidirectional water transport from the superhydrophobic surface to the hydrophilic surface, realizing the function of unidirectional liquid transmission.

[0048] Figure 6 The condensation behavior of water vapor on the side wall of the condensation cycle device 4 is shown. In the droplet nucleation stage, small droplets 9 are formed in the microchannel 7 and on the grid ( Figure 6 b), as the droplets in the microchannel 7 grow and merge, they become elongated liquid columns 10 due to the constraints of the grid and the side walls of the microchannel 7 ( Figure 6 c). Due to the special function of unidirectional water transport of Janus micromembrane 8, small droplets 9 are transported to one side of microchannel 7. Once they contact liquid column 10, the droplets on the grid are immediately absorbed into microchannel 7. As more condensed droplets are absorbed into microchannel 7, the length and volume of liquid column 10 increase, and due to the super hydrophobic property of microchannel 7, gravity causes liquid column 10 to fall off ( Figure 6 d). The detached liquid column provides a new attachment site for the subsequent condensed water vapor, allowing it to enter a new cycle to achieve rapid condensation.

[0049] like Figure 7As shown, the work of the water-absorbing and hygroscopic medium in the evaporative cooling system is mainly divided into two parts: adsorption and evaporation analysis. During the day, the photovoltaic panel 1 generates electricity under the solar radiation, and part of the radiation energy is converted into heat to increase the temperature of the photovoltaic panel 1. The heat is conducted along the photovoltaic panel 1 to the hygroscopic medium below. Based on the thermal conductivity of the hygroscopic medium 1, the heat passes through the hygroscopic medium 3, causing the internal water to evaporate to form water vapor 11 and diffuse downward. The heat migration of the photovoltaic panel 1 caused by the evaporation of water promotes the cooling of the photovoltaic panel 1. When the sun sets, the photovoltaic panel 1 enters a dormant state. At this time, the adsorption capacity of the hygroscopic medium 3 exceeds the desorption capacity, and it continues to absorb moisture in the high humidity environment provided by the condensation circulation device 4 until the sun rises the next day, and the real-time photovoltaic panel 1 is passively cooled and enters a new cycle.

[0050] like Figure 8 As shown, the hygroscopic medium 3 is adsorbed by the hydration and deliquescence of lithium chloride 12: the salt crystal absorbs water molecules in the environment through a hydration reaction to form a hydrate, and then continues to absorb water to gradually dissolve the solid salt, forming a LiCl aqueous solution inside the hygroscopic medium 3. Relying on the water vapor pressure difference between the salt solution and the surrounding environment, the water molecules in the environment are continuously absorbed. This process can be regarded as the dilution of the concentrated LiCl solution by the water vapor 11 in the condensation circulation system 4. When more water molecules are absorbed, the adsorption rate of the hygroscopic medium 3 slows down until the vapor pressure of the salt solution is equal to that of the surrounding environment, and the hygroscopic medium 3 reaches adsorption equilibrium. Thanks to the gel form of the hygroscopic medium 3, the adsorbed water vapor 3 can be converted into liquid water and stored. Even if a large amount of water is stored, the hygroscopic medium 3 is still viscous and can be directly applied to the photovoltaic panel cooling system and attached to the photovoltaic backplane for use as a cooling medium.

[0051] Methods of using the present invention

[0052] The heat generated by the photovoltaic panel 1 when working is used to drive the evaporation of the moisture in the bottom layer of the condensation circulation device 4, thereby providing a high-humidity environment for the adsorption of the hygroscopic medium 3. At the same time, desorption is driven by the heat of the back plate to achieve the purpose of cooling the photovoltaic panel 1. The moisture in the hygroscopic medium 3 in the system reaches a dynamic equilibrium state, which ensures the continuous water storage and cooling capacity of the hygroscopic medium 3, prolongs the passive cooling time of the photovoltaic panel 1, and solves the cooling failure problem caused by insufficient water storage of the hygroscopic medium 3 in the traditional evaporative cooling process of the hygroscopic medium, gets rid of the limitations of natural environmental factors such as drought and water shortage, and provides a new idea for the cooling of photovoltaic cells in severely drought and water-scarce areas.

[0053] Super-hydrophobic microchannel 7-Janus microfilm 8 plays a vital role in cooling water vapor in a closed cavity. These microchannels 7 have hydrophobic surfaces, which can cause condensed water vapor to form water droplets and then slide down quickly, keeping the channel surface dry, thereby continuously and efficiently transferring heat. In a closed environment, when hot fluid or steam flows through the hydrophobic microchannel 7, due to its high thermal conductivity material (copper), heat is quickly absorbed and conducted to the channel wall. Subsequently, water vapor condenses into water droplets on these cooling surfaces. The low surface energy characteristics of the super-hydrophobic surface make it difficult for water droplets to adhere, but roll down along the channel wall and be discharged, producing a dripping effect.

[0054] The design of the hydrophobic microchannel 7 optimizes the condensation process, reduces thermal resistance, and improves heat exchange efficiency. It has a small size, thereby providing a large surface area to volume ratio, further enhancing the condensation efficiency. In addition, this design also helps to reduce pressure drop, making the fluid flow smoother.

[0055] In a closed condensation cycle system, the hydrophobic microchannel 7 can effectively control the internal temperature and improve system stability and performance. By maintaining a lower temperature, the service life of the equipment can be extended and ensure that it operates in an optimal state. In short, the hydrophobic microchannel 7 provides an efficient and reliable solution for effective thermal management in a closed environment.

[0056] Implementation Example

[0057] like Figures 9-11 As shown, under one-time sunlight, using a hygroscopic medium 3 of the same size as the photovoltaic panel 1, the average temperature of the photovoltaic panel 1 surface and back plate is reduced by about 10°C and 15°C respectively, compared with the natural convection cooling of the air, and remains stable. Therefore, the output voltage is increased by 5.1% compared with the photovoltaic panel without this device, providing a new perspective for the uninterrupted passive cooling of solar cells.

[0058] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A zero-energy real-time photovoltaic panel passive cooling device, characterized in that: It comprises a solar evaporative cooling system, a condensing circulation device (4) and a water collecting device (5); the solar evaporative cooling system is arranged above the condensing circulation device (4), and the condensing circulation device (4) and the water collecting device (5) are connected via room temperature cooling water pre-arranged in the water collecting device (5).

2. A zero-energy real-time photovoltaic panel passive cooling device according to claim 1, characterized in that: The solar evaporative cooling system comprises a hygroscopic medium (3); the hygroscopic medium (3) is attached to the back of a photovoltaic panel (1) by virtue of its viscosity.

3. A zero-energy real-time photovoltaic panel passive cooling device according to claim 2, characterized in that: A support net (6) is arranged below the hygroscopic medium (3), and the support net (6) is connected to the photovoltaic panel (1).

4. A zero-energy real-time photovoltaic panel passive cooling device according to claim 2 or 3, characterized in that: A flexible silica gel gasket (2) is placed between the hygroscopic medium (3) and the photovoltaic panel (1).

5. The zero-energy real-time photovoltaic panel passive cooling device according to claim 1, characterized in that: The cold condensation circulation device (4) is an overall enclosed structure that is open at the top and bottom. The side wall of the cold condensation circulation device (4) adopts a super-hydrophobic microchannel (7) structure, and the outer surface of the microchannel (7) is covered with a Janus microfilm (8) that changes from super-hydrophobic to hydrophilic.

6. A zero-energy real-time photovoltaic panel passive cooling device according to claim 5, characterized in that: The main material of the cold condensation circulation device (4) is high thermal conductivity copper. The method for preparing the super-hydrophobic microchannel (7) is as follows: first, the microchannel (7) is continuously ultrasonically cleaned with acetone, anhydrous ethanol and deionized water, and the microchannel (7) is immersed in an ammonia solution. After a period of reaction, the copper surface is covered with Cu(OH)2 nanobelts. After ammonia corrosion, the sample is rinsed with deionized water and dried with a nitrogen flow. Then, the super-hydrophilic microchannel (7) is immersed in a 2mM ethanol solution of n-octadecanethiol, and heated in a constant temperature water bath at 70°C for reaction for 1h. Then, the sample surface is cleaned with anhydrous ethanol to remove the unreacted n-octadecanethiol solution, and finally a microchannel (7) with super-hydrophobic properties is generated.

7. A zero-energy real-time photovoltaic panel passive cooling device according to claim 5 or 6, characterized in that: The Janus micro-membrane (8) uses a 300-mesh copper mesh.

8. A zero-energy real-time photovoltaic panel passive cooling device according to claim 2, characterized in that: The hygroscopic medium (3) uses hydration and deliquescence of lithium chloride (12) for adsorption.

9. A zero-energy real-time photovoltaic panel passive cooling device according to claim 8, characterized in that: When preparing the hygroscopic medium (3), a 0.4 g / mL LiCl solution is used and the proportion is determined according to LiCl ≥ 99%.

10. The zero-energy real-time photovoltaic panel passive cooling device according to claim 1, characterized in that: A condensed water layer is provided in the water collecting device (5).

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