Vacuum tube solar collector coupled with phase change heat storage seawater desalination system and working method

Abstract

The application discloses a seawater desalination system coupled with a phase change heat storage vacuum tube type solar collector and a working method, and the system comprises a vacuum tube type solar collector, a seawater supply tank, a valve, a water pump, a glass cover plate, a thermoelectric module, a fresh water collecting tank, fins, a distilled water channel, a bottom container, corrugated heat absorption plates, a phase change material filling area and a seawater evaporation area; the application combines the technologies of the solar collector, the solar seawater desalination, the temperature difference power generation and the phase change heat storage, can realize the continuous seawater desalination and the temperature difference power generation all day long, and supplies power to the water pump through the temperature difference power generation, significantly reduces the system energy consumption, and realizes the flexible and sufficient utilization of the solar energy and the low-cost and efficient desalination of the seawater resources.

Description

Technical Field

[0001] This invention relates to the technical fields of solar thermal utilization, solar seawater desalination, phase change thermal storage, and thermoelectric power generation, specifically to a seawater desalination system and its operating method using a vacuum tube solar collector coupled with phase change thermal storage. Background Technology

[0002] With the continuous growth of the world's population and the continuous depletion of existing freshwater reserves, the demand for freshwater resources is increasing dramatically. Approximately 98% of the Earth's water is in the oceans, making seawater desalination an effective way to address the current shortage of freshwater resources. Solar distillation seawater desalination technology is one of the important methods for converting seawater into freshwater resources. Active solar distillation seawater desalination technology, by installing collectors, including flat-plate solar collectors, vacuum tube solar collectors, and solar concentrators, first preheats the seawater to increase its temperature, thereby increasing the evaporation rate and ultimately increasing freshwater production. However, traditional solar distillation seawater desalination technology suffers from intermittent system operation due to the lack of sunlight at night and results in significant heat energy waste. Thermal energy storage technology can store heat in different storage media and release it for use when needed. Among various thermal energy storage technologies, phase change thermal energy storage technology has the characteristics of high heat storage density and stable phase change temperature, effectively solving the instability and volatility problems of renewable energy utilization. Summary of the Invention

[0003] To overcome the shortcomings of existing technologies, the present invention aims to provide a seawater desalination system and its operating method that couples a vacuum tube solar collector with phase change thermal storage. By combining the vacuum tube solar collector with traditional solar distillation seawater desalination technology, the evaporation rate of seawater is effectively improved, increasing freshwater production. Through integration with phase change thermal storage technology, not only is freshwater production increased, but the problem of seawater desalination being impossible under conditions of no sunlight at night is also overcome. Utilizing thermoelectric generators for power generation allows for the utilization of waste heat, improving the overall utilization rate of solar energy. This system can achieve 24-hour continuous seawater desalination and thermoelectric power generation, and has advantages such as energy saving, environmental protection, high freshwater yield, and high energy utilization efficiency.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A seawater desalination system coupled with a vacuum tube solar collector and phase change thermal storage includes a vacuum tube solar collector 1, a seawater supply tank 3, a glass cover 8, a first thermoelectric module 9, a first freshwater collection tank 10, a second thermoelectric module 13, a second freshwater collection tank 22, fins 14, a condensate channel 15, a bottom container 16, a corrugated heat absorption plate 17, a phase change material filling area 18, a seawater evaporation area 19, various valves, and a water pump; the vacuum tube solar collector 1... The outlet is connected to the seawater evaporation zone 19 and one water tank of the seawater supply tank 3 via the first three-way valve 2; the other water tank of the seawater supply tank 3 is connected to the second three-way valve 7 via the first water pump 6 and then splits into two paths, which are connected to the inlet of the vacuum tube solar collector 1 and the seawater evaporation zone 19 respectively; the outlet at the lower part of the shaded side of the glass cover 8 is connected to the condensate channel 15 via the first freshwater collection tank 10, the third valve 11 and the second water pump 12; the outlet at the lower part of the sun-facing side of the glass cover 8 is connected to the condensate channel 15 via the first freshwater collection tank 10, the third valve 11 and the second water pump 12; The second freshwater collection tank 22, the fourth valve 21, and the third water pump 20 are connected to the condensate channel 15; the bottom container 16 is connected to the glass cover plate 8 to form a cavity as a closed seawater desalination space, which also serves as insulation; a corrugated heat-absorbing plate 17 and a phase change material filling area 18 are set in the cavity, dividing the cavity into an upper seawater evaporation area 19 and a lower condensate channel 15; the phase change material filling area 18 is located below the corrugated heat-absorbing plate 17 and is used to load the phase change material to store heat; the seawater evaporation area 19 is located above the corrugated heat-absorbing plate 17 and is the main area where seawater desalination occurs; the first thermoelectric module 9 is located above the shaded side of the glass cover plate 8, and the hot end is in close contact with the glass cover plate 8, while the cold end directly exchanges heat with the outside air through natural convection; the hot end of the second thermoelectric module 13 is in contact with the bottom of the phase change material filling area 18, and the cold end is provided with fins 14, which are located in the condensate channel 15 and exchange heat with the condensed freshwater through convection.

[0006] The vacuum tube solar collector 1 is placed facing the sun, with the seawater inlet located at the bottom and the seawater outlet located at the top, serving to preheat the seawater.

[0007] The seawater supply tank 3 is provided with a central removable partition 4, two water inlets and one water outlet; the central removable partition 4 divides the interior of the seawater supply tank 3 into two water tanks, left and right; the seawater supply port 5 is located in the right water tank of the seawater supply tank 3, the seawater inlet after being preheated by the vacuum tube solar collector 1 is located in the left water tank of the seawater supply tank 3; and the water outlet is located in the right water tank of the seawater supply tank 3.

[0008] The glass cover plate 8 is ridge-shaped, with the left side facing the sun at an angle of 30° to the horizontal plane and the right side facing away from the sun at an angle of 45° to the horizontal plane, which serves to condense water vapor; a flow guiding device is installed at the lower edge of the left and right sides of the plate, which serves to collect condensed fresh water and stabilize the flow rate, and guide the condensed fresh water to the first fresh water collection tank 10 and the second fresh water collection tank 22 respectively.

[0009] The fins 14 are made of aluminum or copper to achieve efficient heat dissipation.

[0010] The corrugated heat absorber plate 17 is made of aluminum alloy to achieve efficient heat transfer and storage inside the phase change material.

[0011] The first water pump 6, the second water pump 12, and the third water pump 20 are all non-backflowable; the first water pump 6 is turned on continuously for 24 hours; the second water pump 12 and the third water pump 20 are turned on during daylight hours and turned off at night when there is no sunlight.

[0012] The first three-way valve 2, the second three-way valve 7, the third valve 11, and the fourth valve 21 are all manual valves. The first three-way valve 2 is fully open during daytime sunlight and fully closed during nighttime non-sunlight periods. The second three-way valve 7 is closed only during daytime sunlight periods, while the other two channels are open. During nighttime non-sunlight periods, it is closed only during nighttime non-sunlight periods, while the other two channels are open. The third valve 11 and the fourth valve 21 are open during daytime sunlight periods and closed during nighttime non-sunlight periods.

[0013] The operating method of the seawater desalination system using a vacuum tube solar collector coupled with phase change heat storage is as follows: During daytime sunlight, the second three-way valve 7 is opened, connecting to the lower inlet of the vacuum tube solar collector 1 and the two side passages of the right water tank of the seawater supply tank 3, as well as the first water pump 6 and the first three-way valve 2. Seawater flows from the right water tank of the seawater supply tank 3 through the vacuum tube solar collector 1 for preheating. The preheated seawater is then divided into two parts by the first three-way valve 2. One part flows into the left water tank of the seawater supply tank 3 for storage and use at night to improve the desalination rate at night. The other part flows directly into the seawater evaporation zone 19 for desalination. Sunlight shines through the glass cover plate 8 onto the seawater surface and the corrugated heat absorption plate 17. After absorbing solar energy, the seawater evaporates into water vapor. When the water vapor rises, it is condensed by the glass cover plate 8. After absorbing heat, the corrugated heat-absorbing plate 17 transfers the heat to the phase change material filling area 18 for storage and nighttime use. At the same time, the first thermoelectric module 9 generates electricity under the temperature difference between the shaded side of the glass cover plate 8 and the environment, which is used to power the three water pumps. The condensed fresh water on the glass cover plate 8 flows to the first fresh water collection tank 10 and the second fresh water collection tank 22 through the diversion device. At this time, the third valve 11, the third water pump 12, the fourth valve 21, and the fourth water pump 20 are opened. The condensed water flows through the above valves and water pumps to the condensate channel 15, cooling the cold end of the second thermoelectric module 13. At this time, the second thermoelectric module 13 generates electricity under the temperature difference between the upper phase change material and the lower condensate, which is used to power the already opened water pumps. At the same time, the heated condensate is drawn out from the condensate channel 15 to supply domestic water for residents.

[0014] During the non-sunlight period at night, the second three-way valve 7 is opened, connecting the two passages of the right water tank of the seawater supply tank 3 and the seawater evaporation zone 19. The first water pump 6 is turned on, all passages of the first three-way valve 2 are closed, and the central partition 4 is removed. This allows some of the preheated seawater stored in the left water tank of the seawater supply tank 3 during the day to flow from the outlet located on the right water tank to the seawater evaporation zone 19 to continue desalination. At the same time, the third valve 11, the second water pump 12, the fourth valve 21, and the third water pump 20 are closed. The heat stored in the phase change material is only supplied to seawater desalination. Meanwhile, the first thermoelectric module 9 generates electricity in the same way as in the daytime mode, supplying electricity to the first water pump 6. The freshwater collected in the first freshwater collection tank 10 and the second freshwater collection tank 22 is used for domestic water use.

[0015] Compared with the prior art, the advantages of the present invention are as follows:

[0016] The entire energy source for desalination of seawater in this invention comes from solar energy, resulting in high comprehensive utilization of solar energy and making it energy-saving and environmentally friendly.

[0017] This invention makes full use of water resources. Compared to directly using the produced freshwater for domestic use, this invention first uses the produced condensed freshwater as the cold end of a thermoelectric module to generate electricity through temperature difference, and then uses it for domestic use. This allows for full utilization of the waste heat from the condensed water and reduces the system's electricity costs.

[0018] This invention combines solar distillation seawater desalination technology with phase change thermal storage technology, which not only increases freshwater production but also effectively solves the problem of seawater desalination not being possible at night.

[0019] The system of this invention combines a vacuum tube solar collector with traditional solar distillation seawater desalination technology, which effectively improves the seawater evaporation rate and increases freshwater production.

[0020] The system of this invention utilizes the temperature difference between the inside and outside of the sun-facing side of the glass cover plate to generate electricity in the thermoelectric module, resulting in high waste heat utilization and saving seawater desalination costs. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a seawater desalination system with a vacuum tube solar collector coupled with phase change thermal storage. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] Example

[0024] See Figure 1 The present invention discloses a seawater desalination system coupled with a vacuum tube solar collector and phase change thermal storage, comprising a vacuum tube solar collector 1, a seawater supply tank 3, a glass cover plate 8, a first thermoelectric module 9, a first freshwater collection tank 10, a second thermoelectric module 13, a second freshwater collection tank 22, fins 14, a condensate channel 15, a bottom container 16, a corrugated heat absorption plate 17, a phase change material filling area 18, a seawater evaporation area 19, valves 2, 7, 11, 21, and water pumps 6, 12, 20.

[0025] The following is combined Figure 1 Detailed explanation of the connection relationships between the components:

[0026] The upper outlet of the vacuum tube solar collector 1 is connected to the seawater evaporation zone 19 and the left water tank of the seawater supply tank 3 via the first three-way valve 2. The right water tank of the seawater supply tank 3 is connected to the second three-way valve 7 via the first water pump 6 and then splits into two paths, which are connected to the lower inlet of the vacuum tube solar collector 1 and the seawater evaporation zone 19 respectively. The lower outlet on the left side of the glass cover plate 8 on the sunny side is connected to the condensate channel 15 via the second freshwater collection tank 22, the fourth valve 21 and the third water pump 20. The lower outlet on the right side of the glass cover plate 8 on the shady side is connected to the condensate channel 15 via the first freshwater collection tank 10, the third valve 11 and the second water pump 12. The bottom container 16 is connected to the glass cover plate 8 to form a cavity, which serves as a closed seawater desalination space and also provides insulation. A corrugated heat-absorbing plate 17 and a phase change material filling area 18 are installed in the cavity, dividing the cavity into an upper seawater evaporation area 19 and a lower condensate channel 15. The phase change material filling area 18 is located below the corrugated heat-absorbing plate 17 and is used to load the phase change material to store heat. The seawater evaporation area 19 is located above the corrugated heat-absorbing plate 17 and is the main area where seawater desalination occurs. The first thermoelectric module 9 is located above the shaded side of the glass cover plate 8, and its hot end is in close contact with the glass cover plate 8, while its cold end directly exchanges heat with the outside air through natural convection. The hot end of the second thermoelectric module 13 is in contact with the bottom of the phase change material filling area 18, and its cold end is equipped with fins 14, which are located in the condensate channel 15 and exchange heat with the condensed fresh water through convection.

[0027] The system of this invention has two working modes: daytime and nighttime, and their operating modes are as follows:

[0028] 1. Daytime operation mode

[0029] The second three-way valve 7 is opened, connecting to the lower inlet of the vacuum tube solar collector 1 and the two side passages of the right water tank of the seawater supply tank 3, the first water pump 6, and the first three-way valve 2. Seawater flows from the right water tank of the seawater supply tank 3 through the vacuum tube solar collector 1 for preheating. The preheated seawater is then divided into two parts by the first three-way valve 2. One part flows into the left water tank of the seawater supply tank 3 for storage and nighttime use to improve the desalination rate at night. The other part flows directly into the seawater evaporation zone 19 for desalination. Sunlight shines through the glass cover plate 8 onto the seawater surface and the corrugated heat absorption plate 17. After absorbing solar energy, the seawater evaporates into water vapor. When the water vapor rises, it is condensed by the glass cover plate 8. The corrugated heat absorption plate 17 absorbs the heat and transfers it to the phase change material filling area 18 for storage and nighttime use. At the same time, the first thermoelectric module 9 generates electricity under the temperature difference between the shaded side of the glass cover plate 8 and the environment, which is used to power the water pump. The condensed freshwater on the glass cover plate 8 flows through the diversion device to the first freshwater collection tank 10 and the second freshwater collection tank 22. At this time, the third valve 11, the third water pump 12, the fourth valve 21, and the fourth water pump 20 are opened. The condensed water flows through the above valves and water pumps to the condensate channel 15, cooling the cold end of the second thermoelectric module 13. At this time, the second thermoelectric module 13 generates electricity under the effect of the temperature difference between the phase change material above and the condensate below, supplying electricity to the water pump that has been turned on. At the same time, the heated condensate is drawn out from the condensate channel 15 to supply domestic water for residents.

[0030] 2. Night Operation Mode

[0031] Open the second three-way valve 7, connecting it to the two passages on both sides of the right water tank of the seawater supply tank 3 and the seawater evaporation zone 19, and the first water pump 6. Close all passages of the first three-way valve 2, and remove the central partition 4. This allows some of the preheated seawater stored in the left water tank of the seawater supply tank 3 during the day to flow from the outlet located on the right water tank to the seawater evaporation zone 19 for continued desalination. At the same time, the third valve 11, the second water pump 12, the fourth valve 21, and the third water pump 20 are closed. The heat stored in the phase change material is only supplied to seawater desalination. Meanwhile, the first thermoelectric module 9 generates electricity as in the daytime mode, supplying power to the first water pump 6. The freshwater collected in the first freshwater collection tank 10 and the second freshwater collection tank 22 is used for domestic water use.

Claims

1. A seawater desalination system using a vacuum tube solar collector coupled with phase change thermal storage, characterized in that: The system includes a vacuum tube solar collector (1), a seawater supply tank (3), a glass cover (8), a first thermoelectric module (9), a first freshwater collection tank (10), a second thermoelectric module (13), a second freshwater collection tank (22), fins (14), a condensate channel (15), a bottom container (16), a corrugated heat absorption plate (17), a phase change material filling area (18), a seawater evaporation area (19), various valves, and a water pump; the outlet of the vacuum tube solar collector (1) is connected to a first three-way valve (2). The other water tank of the seawater supply tank (3) is connected to the seawater evaporation zone (19) and the seawater supply tank (3) in one water tank; the other water tank of the seawater supply tank (3) is connected to the second three-way valve (7) through the first water pump (6) and then splits into two paths, which are respectively connected to the inlet of the vacuum tube solar collector (1) and the seawater evaporation zone (19); the lower water outlet of the glass cover (8) on the shaded side is connected to the condensate channel (15) through the first freshwater collection tank (10), the third valve (11) and the second water pump (12); the lower water outlet of the glass cover (8) on the sunny side is connected to the second freshwater collection tank (10) through the second freshwater collection tank (12). The container (22), the fourth valve (21), and the third water pump (20) are connected to the condensate channel (15); the bottom container (16) is connected to the glass cover (8) to form a cavity as a closed seawater desalination space, which also serves as a heat preservation function; a corrugated heat-absorbing plate (17) and a phase change material filling area (18) are provided in the cavity, dividing the cavity into an upper seawater evaporation area (19) and a lower condensate channel (15); the phase change material filling area (18) is located below the corrugated heat-absorbing plate (17) and is used to load the phase change material storage. Heat storage; the seawater evaporation zone (19) is located above the corrugated heat absorption plate (17) and is the main area for seawater desalination; the first thermoelectric module (9) is located above the shaded side of the glass cover plate (8) and the hot end is in close contact with the glass cover plate (8), while the cold end directly exchanges heat with the outside air through natural convection; the hot end of the second thermoelectric module (13) is in contact with the bottom of the phase change material filling area (18), and the cold end is provided with fins (14), which are located in the condensate channel (15) and exchange heat with the condensed fresh water through convection.

2. The seawater desalination system with a vacuum tube solar collector coupled with phase change thermal storage according to claim 1, characterized in that: The vacuum tube solar collector (1) is placed on the sunny side, with the seawater inlet located at the bottom of the vacuum tube solar collector (1) and the seawater outlet located at the top of the vacuum tube solar collector (1), which serves to preheat the seawater.

3. The seawater desalination system with a vacuum tube solar collector coupled with phase change thermal storage according to claim 1, characterized in that: The seawater supply tank (3) is provided with a central detachable partition, two inlets and one outlet; the central detachable partition (4) divides the interior of the seawater supply tank (3) into two water tanks, left and right; the seawater supply port (5) is located in the right water tank of the seawater supply tank (3), the seawater inlet after being preheated by the vacuum tube solar collector (1) is located in the left water tank of the seawater supply tank (3); the outlet is located in the right water tank of the seawater supply tank (3).

4. A seawater desalination system with a vacuum tube solar collector coupled with phase change thermal storage according to claim 1, characterized in that: The glass cover plate (8) is ridge-shaped. The angle between the left side of the glass cover plate (8) facing the sun and the horizontal plane is 30°, and the angle between the right side facing away from the sun and the horizontal plane is 45°, which serves to condense water vapor. A flow guiding device is installed at the lower edge of the left and right sides of the plate to collect condensed fresh water and stabilize the flow rate. The condensed fresh water is directed to the first fresh water collection tank (10) and the second fresh water collection tank (22) respectively.

5. A seawater desalination system with a vacuum tube solar collector coupled with phase change thermal storage according to claim 1, characterized in that: The fins (14) are made of aluminum or copper to achieve efficient heat dissipation.

6. A seawater desalination system with a vacuum tube solar collector coupled with phase change thermal storage according to claim 1, characterized in that: The corrugated heat absorber plate (17) is made of aluminum alloy to achieve efficient heat transfer and storage inside the phase change material.

7. A seawater desalination system with a vacuum tube solar collector coupled with phase change thermal storage according to claim 1, characterized in that: The first water pump (6), the second water pump (12), and the third water pump (20) are all non-returnable; the first water pump (6) is turned on continuously for 24 hours; the second water pump (12) and the third water pump (20) are turned on during daylight hours and turned off at night when there is no light.

8. A seawater desalination system with a vacuum tube solar collector coupled with phase change thermal storage according to claim 1, characterized in that: The first three-way valve (2), the second three-way valve (7), the third valve (11), and the fourth valve (21) are all manual valves. The first three-way valve (2) has all three passages open during daytime sunlight and all closed during nighttime non-sunlight. The second three-way valve (7) has only closed the passage connected to the seawater evaporation zone (19) during daytime sunlight and has the other two passages open. During nighttime non-sunlight, it has only closed the passage connected to the inlet of the vacuum tube solar collector (1) and has the other two passages open. The third valve (11) and the fourth valve (21) are open during daytime sunlight and closed during nighttime non-sunlight.

9. The operating method of a seawater desalination system with a vacuum tube solar collector coupled with phase change thermal storage as described in any one of claims 1 to 8, characterized in that: During daytime sunlight, the second three-way valve (7) is opened, connecting to the lower inlet of the vacuum tube solar collector (1) and the two side passages of the right water tank of the seawater supply tank (3), the first water pump (6), and the first three-way valve (2). Seawater flows from the right water tank of the seawater supply tank (3) through the vacuum tube solar collector (1) for preheating. The preheated seawater is then divided into two parts by the first three-way valve (2). One part flows into the left water tank of the seawater supply tank (3) for storage and nighttime use to improve the nighttime desalination rate. The other part flows directly into the seawater evaporation zone (19) for desalination. Sunlight shines through the glass cover (8) onto the seawater surface and the corrugated heat absorption plate (17). After absorbing solar energy, the seawater evaporates into water vapor. When the water vapor rises, it is condensed by the glass cover (8). The corrugated heat absorption plate (17) absorbs the heat and transfers it. The phase change material is stored in the phase change material filling area (18) for nighttime use. At the same time, the first thermoelectric module (9) generates electricity under the temperature difference between the shaded side of the glass cover (8) and the environment, which is used to supply electricity to the three water pumps. The condensed fresh water on the glass cover (8) flows to the first fresh water collection tank (10) and the second fresh water collection tank (22) through the diversion device. At this time, the third valve (11), the second water pump (12), the fourth valve (21), and the third water pump (20) are opened. The condensed water flows through the above valves and water pumps to the condensate channel (15) to cool the cold end of the second thermoelectric module (13). At this time, the second thermoelectric module (13) generates electricity under the temperature difference between the phase change material above and the condensate below, which supplies electricity to the water pumps that have been opened. At the same time, the heated condensate is drawn out from the condensate channel (15) to supply domestic water for residents. During the non-lighting period at night, the second three-way valve (7) is opened to connect the two passages of the right water tank of the seawater supply tank (3) and the seawater evaporation zone (19), the first water pump (6) is turned on, all passages of the first three-way valve (2) are closed, and the central partition (4) is removed so that some of the preheated seawater stored in the left water tank of the seawater supply tank (3) during the day can flow from the outlet located on the right water tank to the seawater evaporation zone (19) to continue desalination; at the same time, the third valve (11), the second water pump (12), the fourth valve (21), and the third water pump (20) are closed, and the heat stored in the phase change material is only supplied to the seawater desalination. Meanwhile, the first thermoelectric module (9) generates electricity in the same way as in the daytime mode to supply the first water pump (6) with electricity. The freshwater collected by the first freshwater collection tank (10) and the second freshwater collection tank (22) is used for domestic water use.

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