Photothermal evaporation and radiation refrigeration realize all-weather seawater desalination device and method

Abstract

The application provides a device and method for realizing continuous seawater desalination day and night through photo-thermal evaporation and radiation refrigeration. The device comprises a light-transmitting glass, a photo-thermal layer, a condensing end, a shell, an evaporation end heat insulation plate, a seawater storage end, a fresh water storage end and a phase change heat storage material. The photo-thermal layer constitutes a central evaporation end, the condensing end and the shell constitute a peripheral radiation refrigeration condensing interface, and the central high-temperature evaporation zone and the peripheral low-temperature condensing zone are formed through the evaporation end heat insulation plate. During the day, seawater is heated and evaporated, then preferentially migrates to the peripheral condensing end and condenses, thereby reducing the condensation of the light-transmitting glass and blocking light; at night, the phase change heat storage material releases heat to maintain evaporation, and the condensing end continuously condenses. The device can also use a seawater collection pipe, a seawater filter screen and a pressure adjusting pipe to realize passive water replenishment and improve the stability of fresh water collection.

Description

Technical Field

[0001] This invention belongs to the field of solar energy utilization technology, specifically relating to a device and method for all-weather seawater desalination using photothermal evaporation and radiative cooling. Background Technology

[0002] Water scarcity is a long-standing and significant problem facing coastal, island, and remote areas. Seawater reserves are abundant, and utilizing renewable energy sources such as solar power for desalination is an important way to obtain freshwater resources. Existing solar-powered seawater desalination devices typically use solar radiation to heat seawater, causing it to evaporate into water vapor, which is then condensed into freshwater through a condensation surface. These devices have advantages such as a wide range of energy sources, relatively simple structure, and low operating costs.

[0003] However, existing solar-powered seawater desalination devices still have certain shortcomings in practical applications. Firstly, some solar-powered seawater desalination devices typically use a top-transparent cover to receive solar radiation, while simultaneously utilizing the top or near-top structure as a condensation surface. As the water vapor formed from seawater evaporation rises, it easily condenses on the surface of the transparent area, forming a water film or droplets, reducing solar transmittance and decreasing the effective solar radiation entering the evaporation end, thus affecting subsequent evaporation efficiency. Secondly, the thermal insulation between the evaporation and condensation areas in existing devices is insufficient. The evaporation end heats up under solar radiation, and the condensation surface is also easily affected by heat from the evaporation end and the device's interior, leading to a reduced temperature difference between the condensation surface and the water vapor, resulting in insufficient condensation driving force. With reduced condensation efficiency, the water vapor inside the device cannot be converted into fresh water in a timely manner, not only reducing freshwater acquisition efficiency but also potentially exacerbating condensation problems in the transparent area.

[0004] Furthermore, conventional solar-powered seawater desalination plants primarily rely on daytime solar radiation to provide heat for evaporation. At night or when solar radiation is insufficient, the evaporation process weakens significantly or even stops, making nighttime hours difficult to utilize effectively. Maintaining continuous desalination typically requires additional energy input or complex auxiliary equipment, which is not conducive to low-cost, passive operation of such plants in coastal or island settings.

[0005] Meanwhile, for seawater desalination plants located in coastal areas, the method of seawater replenishment also affects the long-term operational capability of the plant. Relying on manual, periodic water replenishment results in high maintenance costs; using external pumps for water replenishment increases energy consumption and structural complexity. Therefore, how to achieve automatic seawater replenishment, separate operation of evaporation and condensation zones, continuous desalination at night, and stable freshwater collection without introducing external energy sources is a technical problem that needs to be solved for further improvement of solar-powered seawater desalination plants. Summary of the Invention

[0006] In view of this, the present invention proposes a solar seawater desalination device and method that combines photothermal evaporation and radiative cooling. The device can be installed in coastal areas, and desalination is carried out 24 hours a day through solar evaporation and radiative cooling at night. It aims to solve the problems of existing solar seawater desalination devices, such as easy condensation and light blocking by the light-transmitting cover, insufficient condensation efficiency due to thermal coupling between the evaporation zone and the condensation zone, easy secondary evaporation due to heat in the freshwater collection area, lack of continuous evaporation heat source at night, and reliance on manual operation for water replenishment in coastal scenarios.

[0007] To solve the above problems, the present invention places the photothermal evaporation end inside the device, and the condensation end and the outer shell, which are made of integrated photonic solar energy reflection and radiation cooling materials, on the outer periphery of the device. A thermal insulation plate is used to form a thermal isolation between the two, so that a radial composite temperature field is formed inside the device where a central high-temperature evaporation zone and a peripheral low-temperature condensation zone coexist. This induces water vapor to migrate from the central evaporation end to the peripheral condensation end and condense.

[0008] The technical solution adopted by this invention to solve the technical problem is: A device for all-weather seawater desalination through photothermal evaporation and radiative cooling is characterized in that the device includes a condensing end, a heat insulation ring, transparent glass, a photothermal layer, a heat insulation layer, a water transmission channel, an outer shell, an evaporation end heat insulation plate, a freshwater collection tank, a seawater collection pipe, a seawater filter screen, a freshwater storage end, a seawater storage end, a phase change thermal storage material, a dew collection tank, a condensate collection pipe, a pressure regulating pipe, and a transparent baffle. The condensing end and the outer shell (using integrated photonic solar energy reflection and radiation cooling materials, which reflect sunlight while having a high mid-infrared emissivity and radiate heat to the outside, forming an annular low-temperature condensing area with a temperature lower than that of the evaporating end area inside the device, used to preferentially attract water vapor to the outer condensing end for condensation; the annular cavity formed by the evaporating end heat insulation plate and the outer shell is used to guide fresh water flowing down along the condensing end; the continuous radiation cooling of the outer shell forms a low-temperature area in the cavity). The heat insulation ring is made of heat insulation material and is placed between the transparent glass and the condenser end to reduce the temperature influence of the transparent glass on the radiant cooling structure; at the same time, the transparent glass, heat insulation ring and condenser end are made into a whole to form a cover plate of a sealing device, which can also be removed; The light-transmitting glass adopts a transparent glass convex lens structure. The selected glass material has good light transmittance and heat preservation effect. Due to the guiding effect of the condensation end on water vapor, the light-transmitting glass does not need to be covered with hydrophobic material. The photothermal layer, the insulation layer, and the water transport channel constitute the central evaporation end located inside the device. The condensation end is arranged in a ring around the outer periphery of the central evaporation end and together with the outer shell, forms a circumferential radiative cooling and condensation interface. The evaporation end insulation plate is disposed between the central evaporation end and the circumferential radiative cooling and condensation interface, so that a radial composite temperature field is formed inside the device, separating the central high-temperature evaporation zone and the outer low-temperature condensation zone while allowing water vapor to communicate. The radial composite temperature field is used to induce water vapor generated by the photothermal layer to preferentially migrate to the condensation end and condense, thereby reducing the accumulation of water vapor on the inner surface of the transparent glass. The evaporator end insulation plate separates the inner evaporator end from the outer condensation and fresh water collection end, forming an insulation area between the evaporator end and the collection end. An annular freshwater collection cavity is formed between the evaporator end insulation plate and the outer shell, located outside the central evaporator end. The annular freshwater collection cavity is sequentially connected to the condenser end, the freshwater collection tank, and the condensate collection pipe, so that the condensed freshwater formed at the condenser end can enter the freshwater storage end along the outer peripheral path. The radiative cooling effect of the outer shell and the heat insulation effect of the evaporator end insulation plate together reduce the probability of the freshwater in the annular freshwater collection cavity being heated and evaporating again. The seawater collection pipe is externally connected to the seawater filter screen and internally connected to the lower side of the seawater storage end. The phase change thermal storage material is placed in the seawater storage end, located on the upper side near the photothermal layer, and absorbs solar thermal energy during the day. The seawater filter can filter out impurities such as mud, sand, and marine organisms while ensuring that seawater can enter the device smoothly. The freshwater storage end collects the condensed freshwater generated inside the device and the dew generated on the outer wall of the radiant cooling plate, and is located at the bottom of the device. When the device is in use, this part will be buried under mud and sand to form a heat insulation area and reduce the chance of secondary heating and evaporation of the condensed freshwater. The seawater storage end is used to store seawater to be desalinated and phase change thermal storage materials. The dew collection trough is an annular inclined surface used to collect dew flowing down the outer wall. A small hole is opened at the lowest point of the inclined surface and is placed above the fresh water storage end to form a relatively closed fresh water collection and storage space. The condensate collection pipe is connected to the freshwater collection tank, guiding the collected condensate into the freshwater storage end. The pressure regulating pipe is a thin tube located at the upper part of the seawater storage end, which passes through the heat insulation plate and the outer shell of the evaporation end and is connected to the outside. It is used to regulate the air pressure inside the device, effectively preventing the device from being damaged due to excessive pressure after being heated by solar thermal energy. At the same time, the device can automatically replenish water through the principle of communicating vessels. The transparent baffle is made of a transparent material that does not affect radiative cooling. It is placed on the dew collection tank and forms a cavity with the outside of the condensation end to receive the dew flowing down the outer shell and guide the condensed fresh water flowing out of the inside into the fresh water storage end.

[0009] The aforementioned all-weather seawater desalination device, which achieves desalination through photothermal evaporation and radiative cooling, is characterized in that: the photothermal layer is a photothermal hydrophilic fabric formed by a composite of carbon fiber and cotton yarn, wherein the cotton yarn forms capillary water transport channels, and the carbon fiber forms a photothermal absorption and evaporation interface, so that the seawater transported by the water transport channel is distributed on the surface of the photothermal layer and undergoes interface evaporation; the heat insulation layer is made of polymer foam and is disposed below the photothermal layer to reduce the heat conduction loss from the photothermal layer to the seawater storage end; the water transport channel is made of hydrophilic material and connects the seawater storage end and the photothermal layer; the phase change thermal storage material is a paraffin-based phase change material with a surface-loaded photothermal carbon-based material and is disposed on the side of the seawater storage end near the water transport channel.

[0010] The aforementioned all-weather seawater desalination device, which achieves desalination through photothermal evaporation and radiative cooling, is characterized in that the phase change thermal storage material absorbs residual heat from the photothermal layer and the vicinity of the seawater storage end during the day and undergoes phase change thermal storage; when external seawater is replenished into the seawater storage end through the seawater collection pipe, the phase change thermal storage material releases latent heat to the newly replenished seawater to preheat the seawater before it enters the water transmission channel; at night or under low solar irradiance conditions, the phase change thermal storage material continues to release heat to the seawater storage end to maintain water vapor generation inside the device.

[0011] A daytime seawater desalination method using a photothermal evaporation and radiative cooling all-weather seawater desalination device, characterized in that the method includes: During the day, sunlight enters the device through the transparent glass and irradiates the photothermal layer. Seawater in the seawater storage end is transported to the photothermal layer through the water transmission channel and forms water vapor under the action of light and heat. The condensing end and the outer shell form a low-temperature condensing zone around the central evaporating end through radiative cooling. The heat insulation plate of the evaporating end thermally isolates the central evaporating end from the low-temperature condensing zone around the periphery, so that the water vapor migrates from the central evaporating end to the peripheral condensing end and condenses, rather than preferentially condensing on the inner surface of the transparent glass. The condensed freshwater enters the annular freshwater collection cavity along the condensing end and flows into the freshwater storage end through the freshwater collection tank and the condensate collection pipe.

[0012] A nighttime seawater desalination method for an all-weather seawater desalination device that utilizes photothermal evaporation and radiative cooling, characterized in that the method comprises: At night, the phase change thermal energy storage material, which completed its heat storage during the day, releases latent heat into the seawater in the seawater storage end, causing the device to continue to generate water vapor and maintain a high water vapor content. At the same time, the condensing end and the outer shell continue to radiate heat to the outside through radiative cooling, forming a low-temperature condensation zone around the central evaporating end. This causes the internal water vapor to condense preferentially at the condensing end, and the condensed freshwater flows into the freshwater storage end through the condensate collection pipe. The dew formed on the outer wall of the outer shell enters the freshwater storage end along the dew collection trough.

[0013] An automatic seawater replenishment method for an all-weather seawater desalination device that achieves desalination through photothermal evaporation and radiative cooling is characterized in that the method utilizes the aforementioned all-weather seawater desalination device that achieves desalination through photothermal evaporation and radiative cooling, and the method includes: The seawater collection pipe and device are positioned below the surface of the coastal beach, with the seawater filter screen located where it can be submerged by high tide. When the high tide submerges the seawater filter screen, the seawater is filtered and enters the seawater collection pipe. Under the condition of air pressure balance formed by the pressure regulating pipe and the outside, it enters the seawater storage end according to the principle of communicating vessels. When the liquid level in the seawater storage end corresponds to the liquid level of the external seawater, water replenishment stops, thereby achieving passive seawater replenishment without external pumping. The beneficial effects of this invention are as follows:

[0014] (1) Reduce condensation and light blocking on transparent glass.

[0015] Since the condenser end and the outer shell form a circumferential radiative cooling condensation interface, water vapor preferentially migrates to the outer low-temperature region and condenses, reducing the formation of water film or fog droplets on the inner surface of the transparent glass, thereby improving the stability of daytime light transmission.

[0016] (2) Increase the driving force of condensation.

[0017] Because the heat insulation plate at the evaporation end thermally isolates the central evaporation end from the outer condensation end, a radial temperature gradient is formed inside the device, with a high temperature at the center and a low temperature at the outer periphery, which is beneficial to improving the water vapor condensation rate.

[0018] (3) Reduce secondary evaporation of freshwater.

[0019] The condensed freshwater enters the freshwater storage end along the outer annular cavity, and this path is affected by the combined effect of the outer shell's radiative cooling and the evaporation end's heat insulation plate, reducing the probability of the collected freshwater being heated and evaporated again.

[0020] (4) Improve the ability to continuously dilute at night.

[0021] Phase change thermal energy storage materials store heat during the day and release latent heat at night to maintain water vapor generation at the seawater storage end; the radiative cooling condensation end continues to provide a low-temperature condensation interface at night, thereby extending the effective desalination time of the device.

[0022] (5) Achieve passive water replenishment.

[0023] The combination of seawater collection pipe, seawater filter screen and pressure regulating pipe enables the device to passively replenish water by utilizing tidal level difference and the principle of communicating vessels, reducing the need for manual water replenishment or external pumping. Attached Figure Description

[0024] Figure 1This is a schematic diagram of a seawater desalination device that achieves all-weather seawater desalination through photothermal evaporation and radiative cooling. Figure 2 for Figure 1 Schematic diagram of the photothermal evaporation section; Figure 3 for Figure 1 A schematic diagram of the device performing seawater desalination during the day; Figure 4 for Figure 1 A schematic diagram of the desalination process performed by the device at night; Among them, 1-condensing end, 2-insulation ring, 3-transparent glass, 4-photothermal layer, 5-insulation layer, 6-water transmission channel, 7-shell, 8-evaporating end insulation plate, 9-freshwater collection tank, 10-seawater collection pipe, 11-seawater filter screen, 12-freshwater storage end, 13-seawater storage end, 14-phase change thermal storage material, 15-dew collection tank, 16-condensate collection pipe, 17-pressure regulating pipe, 18-transparent baffle. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments: As attached Figure 1 To be continued Figure 4 As shown, this invention provides a device for all-weather seawater desalination through photothermal evaporation and radiative cooling. The device includes a condenser end 1, a heat insulation ring 2, a translucent glass 3, a photothermal layer 4, a heat insulation layer 5, a water transmission channel 6, an outer shell 7, an evaporation end heat insulation plate 8, a freshwater collection tank 9, a seawater collection pipe 10, a seawater filter screen 11, a freshwater storage end 12, a seawater storage end 13, a phase change thermal energy storage material 14, a dew collection tank 15, a condensate collection pipe 16, a pressure regulating pipe 17, and a transparent baffle 18.

[0026] The photothermal layer 4, the insulation layer 5, and the water transport channel 6 constitute the central evaporation end located inside the device. The condensation end 1 is arranged in a ring around the outer periphery of the central evaporation end and together with the outer shell 7, forms a circumferential radiative cooling condensation interface. The evaporation end insulation plate 8 is disposed between the central evaporation end and the outer peripheral condensation collection area to reduce heat conduction from the central evaporation end to the outer peripheral condensation collection area. Through the above structural arrangement, a radial composite temperature field is formed inside the device, where a central high-temperature evaporation zone and an outer low-temperature condensation zone coexist. This causes the water vapor generated by the photothermal layer 4 to preferentially migrate to and condense at the outer peripheral condensation end 1, rather than preferentially accumulating on the inner surface of the transparent glass 3.

[0027] The condenser end 1 and the outer shell 7 are made of integrated photonic solar energy reflective and radiative cooling materials. This material reflects a portion of solar radiation and has a high emissivity in the mid-infrared band, thus radiating heat to the outside. Since the condenser end 1 is located in the outer periphery of the central evaporator end and is thermally isolated from it by the evaporator end insulation plate 8, a relatively low-temperature circumferential condensation interface can be formed inside the device. After water vapor is generated at the central evaporator end, it moves towards the condenser end 1 under the influence of temperature and water vapor concentration gradients, and condenses into fresh water on the surface of the condenser end 1. This reduces the formation of water mist or water film on the inner surface of the transparent glass 3, maintaining the light-passing ability of the transparent glass 3.

[0028] The heat insulation ring 2 is made of heat-insulating material and is positioned between the transparent glass 3 and the condenser end 1. The heat insulation ring 2 serves two purposes: firstly, it reduces heat transfer between the transparent glass 3 and the condenser end 1, mitigating the impact of temperature changes in the transparent glass 3 on the radiative cooling effect of the condenser end 1; secondly, the transparent glass 3, the heat insulation ring 2, and the condenser end 1 together form a removable cover structure. This cover structure allows the device to be sealed during operation and can be removed when necessary to clean salt or other deposits.

[0029] The light-transmitting glass 3 employs a transparent glass convex lens structure to allow external sunlight to enter the device and enhance the effect of sunlight converging towards the central evaporation end. Since this invention preferentially condenses water vapor through the outer peripheral condensation end 1, the light-transmitting glass 3 no longer serves as the primary condensation surface, thus reducing the obstruction of incident light by condensation on the inner surface of the light-transmitting glass 3.

[0030] The photothermal layer 4 absorbs solar radiation introduced by the transparent glass 3 and converts it into heat. The photothermal layer 4 can be made of a photothermal hydrophilic fabric composed of carbon fiber and cotton yarn, where the cotton yarn forms a capillary water transport network and the carbon fiber forms the photothermal absorption and interfacial evaporation areas. Seawater in the seawater storage end 13 is transported to the photothermal layer 4 via the water transport channel 6, where it is heated on the surface of the photothermal layer 4 and undergoes interfacial evaporation. An insulation layer 5 is disposed below the photothermal layer 4 to reduce heat conduction loss from the photothermal layer 4 to the seawater storage end 13, allowing more solar heat to concentrate at the photothermal evaporation interface. The water transport channel 6 is made of a hydrophilic material and connects the seawater storage end 13 and the photothermal layer 4, continuously transporting seawater to the photothermal layer 4 using capillary action.

[0031] An evaporator-end insulation plate 8 is positioned between the central evaporator end and the outer condensation collection area. The evaporator-end insulation plate 8 not only reduces heat diffusion from the central evaporator end to the outer periphery but also forms an annular freshwater collection cavity with the outer shell 7. The condensed freshwater formed on the surface of the condenser end 1 flows downwards along its surface and enters this annular freshwater collection cavity, then passes through the freshwater collection tank 9 and the condensate collection pipe 16 into the freshwater storage end 12. Because this annular freshwater collection cavity is located near the outer radiative cooling area and is isolated from the central high-temperature evaporator end by the evaporator-end insulation plate 8, the probability of secondary evaporation of the condensed freshwater due to heating can be reduced.

[0032] The freshwater collection tank 9 has an annular inclined structure, used to guide the freshwater flowing down along the condensation end 1 and the annular cavity into the condensate collection pipe 16. The condensate collection pipe 16 is connected to the freshwater storage end 12, used to transport the condensed freshwater formed inside the device to the freshwater storage end 12. The freshwater storage end 12 is located at the bottom of the device. When the device is in use, this part can be buried below the surface of the sand beach to reduce the impact of external solar radiation and ambient heat on the collected freshwater, thereby improving the stability of freshwater storage.

[0033] The seawater storage end 13 is used to store seawater to be desalinated and to house the phase change thermal energy storage material 14. The phase change thermal energy storage material 14 is disposed within the seawater storage end 13, and is preferably arranged on the side close to the photothermal layer 4 and the water transmission channel 6. The phase change thermal energy storage material 14 can be a paraffin-based phase change material with a surface-loaded photothermal carbon-based material. During daytime operation, the phase change thermal energy storage material 14 absorbs heat from the vicinity of the photothermal layer 4 and the upper region of the seawater storage end 13 and undergoes phase change thermal energy storage. When new seawater is replenished into the seawater storage end 13 through the seawater collection pipe 10, the phase change thermal energy storage material 14 can release latent heat to the newly replenished seawater at a lower temperature, preheating the seawater before it enters the water transmission channel 6. At night or when solar radiation is insufficient, the phase change thermal energy storage material 14 continues to release the heat stored during the day, so that a certain amount of water vapor can still be generated in the seawater storage end 13, thereby extending the effective desalination time of the device.

[0034] The seawater collection pipe 10 is connected to the seawater storage end 13, and a seawater filter screen 11 is installed on its exterior. The seawater filter screen 11 is used to perform preliminary filtration of the seawater entering the seawater collection pipe 10, reducing the entry of silt, marine organisms, or other impurities into the device. The pressure regulating pipe 17 is located at the top of the seawater storage end 13, and passes through the evaporator end heat insulation plate 8 and the outer shell 7 before connecting to the outside. The pressure regulating pipe 17 serves two purposes: firstly, it balances the air pressure between the inside of the device and the outside, reducing the risk of damage to the device due to increased internal pressure after it is heated during the day; secondly, the pressure regulating pipe 17, in conjunction with the seawater collection pipe 10, allows the seawater storage end 13 to passively replenish water under pressure equilibrium based on the principle of communicating vessels.

[0035] A dew collection tank 15 is located on the lower outer side of the outer casing 7 and has an annular sloping structure. Because the outer casing 7 uses radiative cooling material, at night or under suitable environmental conditions, the temperature of the outer wall of the outer casing 7 decreases, causing water vapor in the air to condense on its outer surface to form dew. The dew flows down the outer wall of the outer casing 7 and enters the dew collection tank 15, eventually flowing into the freshwater storage end 12. A transparent baffle 18 is located above the dew collection tank 15 and forms a relatively enclosed guiding space with the outside of the condensation end 1 to reduce dew loss and guide the condensed dew on the outer wall into the freshwater storage end 12. The transparent baffle 18 is made of a transparent material that does not significantly affect the radiative cooling process.

[0036] During daytime operation, sunlight enters the device through the transparent glass 3 and is concentrated onto the photothermal layer 4. Seawater in the seawater storage end 13 is transported to the photothermal layer 4 via the water transmission channel 6, where it evaporates and forms water vapor on the surface of the photothermal layer 4. Simultaneously, the condensing end 1 and the outer shell 7 radiate heat to the outside through radiative cooling, forming a low-temperature condensation zone around the central evaporating end. Because the evaporating end insulation plate 8 thermally isolates the central evaporating end from the peripheral condensation collection area, a radial composite temperature field is formed inside the device, where a central high-temperature evaporating zone and a peripheral low-temperature condensation zone coexist. This radial composite temperature field causes water vapor to preferentially migrate from the central evaporating end to the peripheral condensing end 1, condensing into fresh water on the surface of the condensing end 1, thereby reducing water vapor condensation on the inner surface of the transparent glass 3. The condensed fresh water then flows along the condensing end 1 into the annular fresh water collection cavity formed between the evaporating end insulation plate 8 and the outer shell 7, and then enters the fresh water storage end 12 via the fresh water collection tank 9 and the condensate collection pipe 16.

[0037] During nighttime operation, although external solar radiation weakens or disappears, the phase change thermal energy storage material 14, which has stored heat during the day, can release latent heat into the seawater in the seawater storage end 13, increasing the seawater's ability to evaporate into water vapor and maintaining a certain water vapor content inside the device. Simultaneously, the condenser end 1 and the outer shell 7 continue to radiate heat to the outside through radiative cooling, keeping the surrounding area at a relatively low temperature. Water vapor inside the device condenses on the surface of the condenser end 1 and flows into the freshwater storage end 12 through the condensate collection pipe 16. Dew formed on the outer wall of the outer shell 7 under the low nighttime conditions enters the dew collection tank 15 along the outer surface of the outer shell 7 and is then guided into the freshwater storage end 12. Thus, the device can continue to utilize the heat released by the phase change thermal energy storage material 14 and the condensation conditions created by radiative cooling at night, improving its nighttime freshwater acquisition capacity.

[0038] When used in coastal areas, a pit can be pre-dug in the sand to accommodate the lower part of the device. The seawater collection pipe 10 and the lower part of the device are placed below the surface of the sand, and the seawater filter screen 11 is positioned so that it can be submerged by the high tide. When the high tide submerges the seawater filter screen 11, the seawater enters the seawater collection pipe 10 after being filtered by the seawater filter screen 11. Because the pressure regulating pipe 17 is connected to the outside, the air pressure inside the seawater storage end 13 can be kept in balance with the outside, and seawater can enter the seawater storage end 13 according to the principle of communicating vessels. When the liquid level in the seawater storage end 13 corresponds to the liquid level of the outside seawater, the water replenishment process tends to stop. Thus, the device can achieve passive seawater replenishment by utilizing the tidal process, without the need for external pumping equipment or frequent manual water replenishment.

[0039] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A device for all-weather seawater desalination through photothermal evaporation and radiative cooling, characterized in that, The device includes a condenser end (1), a heat insulation ring (2), a transparent glass (3), a photothermal layer (4), a heat insulation layer (5), a water transmission channel (6), an outer shell (7), an evaporator end heat insulation plate (8), a freshwater collection tank (9), a seawater collection pipe (10), a seawater filter screen (11), a freshwater storage end (12), a seawater storage end (13), a phase change heat storage material (14), a dew collection tank (15), a condensate collection pipe (16), a pressure regulating pipe (17), and a transparent baffle (18). The condensing end (1) and the outer shell (7) are made of integrated photonic solar energy reflection and radiation cooling materials. While reflecting sunlight, they have a high mid-infrared emissivity and radiate heat to the outside. A ring-shaped low-temperature condensing area with a temperature lower than that of the evaporating end area is formed in the circumference of the device. This is used to preferentially attract water vapor to the outer condensing end (1) for condensation. The ring-shaped cavity formed by the evaporating end heat insulation plate (8) and the outer shell (7) is used to guide the fresh water flowing down along the condensing end (1). The continuous radiation cooling of the outer shell (7) forms a low-temperature area in the cavity. The heat insulation ring (2) is made of heat insulation material and is placed between the light-transmitting glass (3) and the condensing end (1) to reduce the temperature influence of the light-transmitting glass (3) on the radiant cooling structure; at the same time, the light-transmitting glass (3), the heat insulation ring (2) and the condensing end (1) are made into a whole to form a cover plate of a sealing device, which can also be removed. The light-transmitting glass (3) adopts a transparent glass convex lens structure. The selected glass material has good light transmittance and heat preservation effect. Due to the guiding effect of the condensing end (1) on water vapor, the light-transmitting glass (3) does not need to be covered with hydrophobic material. The photothermal layer (4), the heat insulation layer (5), and the water transmission channel (6) constitute the seawater evaporation end. The seawater evaporates at the interface on the photothermal layer (4) through the thermal energy of sunlight, and water is transferred between the seawater and the water body through the water transmission channel (6). The heat insulation layer (5) is used to reduce heat conduction loss. The evaporation end insulation plate (8) separates the inner evaporation end part from the outer condensation and fresh water collection part, forming an insulation area between the evaporation end and the collection end; The evaporator end heat insulation plate (8) and the outer shell (7) are arranged to form an annular cavity in the middle, which is used to collect the fresh water collected by the condenser end (1). The fresh water collection tank (9) is an annular inclined surface, which guides the condensed fresh water through the condensate collection pipe (16) into the fresh water storage end (12). The seawater collection pipe (10) is connected to the seawater filter screen (11) on the outside and connected to the lower side of the seawater storage end (13) on the inside. The phase change thermal storage material (14) is placed in the seawater storage end (13) and located on the upper side near the photothermal layer (4) to absorb solar thermal energy during the day. The seawater filter (11) can filter impurities such as mud, sand, and marine organisms while ensuring that seawater can smoothly enter the device. The freshwater storage end (12) collects the condensed freshwater generated inside the device and the dew generated on the outer wall of the radiant cooling plate, and is located at the bottom of the device. When the device is in use, this part will be buried under mud and sand to form a heat insulation area to reduce the chance of secondary heating and evaporation of the condensed freshwater. The seawater storage end (13) is used to store seawater to be desalinated and phase change thermal energy storage material (14). The dew collection trough (15) is an annular inclined surface used to collect dew flowing down the outer wall. A small hole is opened at the lowest point of the inclined surface and placed above the fresh water storage end (12) to form a relatively closed fresh water collection and storage space. The condensate collection pipe (16) is connected to the freshwater collection tank (9) to guide the condensate collected inside into the freshwater storage end (12). The pressure regulating pipe (17) is a thin pipe located above the seawater storage end (13), which passes through the evaporation end insulation plate (8) and the outer shell (7) and is connected to the outside. It is used to regulate the air pressure inside the device, effectively preventing the device from being damaged due to excessive pressure after being heated by solar energy. At the same time, the device can automatically replenish water through the principle of communicating vessels. The transparent baffle (18) is made of a transparent material that does not affect radiative cooling. It is placed on the dew collection tank (15) and forms a cavity with the outside of the condensation end (1). It receives the dew flowing down along the outer shell (7) and guides the condensed fresh water flowing out of the interior into the fresh water storage end (12).

2. The all-weather seawater desalination device according to claim 1, characterized in that, The photothermal layer (4) is a mixed fabric of carbon fiber and cotton yarn. Seawater is transferred from the cotton yarn to the carbon fiber through capillary action. The carbon fiber has a high light absorption rate and photothermal conversion efficiency. The heat insulation layer (5) is made of polymer foam, which has high heat insulation performance and ensures the evaporation efficiency of the photothermal layer (4). The water transmission channel (6) is made of hydrophilic degreased cotton, which can transmit seawater in the lower seawater storage end (13) to the upper photothermal layer (4). The phase change heat storage material (14) is made by coating the surface of paraffin with photothermal conversion carbon-based material using a surface modification method. It can absorb and store ambient heat energy and release it at night or in low temperature conditions.

3. The all-weather seawater desalination device according to claim 1, characterized in that, After new seawater enters the seawater storage end (13) through the seawater collection pipe (10), the phase change thermal storage material (14) can perform phase change heat release and preheat the seawater because the temperature of the newly replenished seawater is low. The preheated seawater enters the photothermal layer (4) after passing through the water transmission channel (6), which accelerates the rate of seawater evaporation of the device.

4. A daytime seawater desalination method using a photothermal evaporation and radiative cooling all-weather seawater desalination device according to claim 1, characterized in that, The method includes: During the day, sunlight shines on the transparent glass (3) and is collected by the convex lens, then shines on the photothermal layer (4) at the evaporation end. After being heated, the seawater turns into water vapor and moves upward. At the same time, the phase change heat storage material (14) absorbs heat. Since the condensing end (1) uses radiation cooling material to continuously radiate heat to outer space, the temperature of the condensing end (1) is lower than that of other parts. When the water vapor encounters the condensing end (1) with a lower temperature, it turns and condenses into fresh water at the condensing end (1), preventing water mist from forming on the transparent glass (3) and ensuring the efficiency of sunlight irradiation. Subsequently, the condensed fresh water flows along the inclined surface into the cavity formed by the outer shell (7) and the heat insulation plate (8) at the evaporation end and enters the condensate collection pipe (16) through the fresh water collection tank (9) and finally flows into the fresh water storage end (12).

5. A nighttime seawater desalination method for a seawater desalination device that achieves all-weather seawater desalination through photothermal evaporation and radiative cooling as described in claim 1, characterized in that, The method includes: At night, due to the continuous irradiation and temperature rise during the day, the phase change thermal storage material (14) has a high latent heat of phase change. It converts solar energy into thermal energy through the photothermal absorption coating. The phase change material undergoes a phase change to store solar thermal energy. At night, the phase change thermal storage material (14) releases thermal energy and evaporates the seawater in the seawater storage end (13) into water vapor, which increases the water vapor content in the air inside the device. At the same time, the condenser end (1) continues to radiate heat into space. Its surface temperature is lower than other parts. The high content of water vapor in the air is passively condensed on the surface of the condenser end (1) and eventually flows into the fresh water storage end (12) through the condensate collection pipe (16). Meanwhile, the water vapor in the air will condense on the outside of the condenser end (1) and flow into the fresh water storage end (12) along the dew collection tank (15).

6. A method for automatic seawater replenishment in an all-weather seawater desalination device based on photothermal evaporation and radiative cooling as described in claim 1, characterized in that, The method utilizes the all-weather seawater desalination device described in any one of claims 1 to 5, which achieves desalination through photothermal evaporation and radiative cooling. The method includes: When using this device, it should be installed on a beach in a coastal area. The seawater collection pipe (10) and the lower half of the device should be placed below the surface of the beach and fixed. The outer part of the seawater collection pipe (10) should be slightly higher than the surface of the beach, and the seawater filter screen (11) should be partially exposed. The device should be installed in an area where the seawater can submerge the seawater filter screen (11) during normal high tide.

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