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

Abstract

The invention discloses a vacuum tube type solar heat collector coupled phase change heat storage seawater desalination system and a working method. The system comprises a vacuum tube type solar thermal collector, a seawater supply box, a valve, a water pump, a glass cover plate, a thermoelectric module, a fresh water collection box, fins, a distilled water channel, a bottom container, a corrugated heat absorption plate, a phase change material filling area and a seawater evaporation area. According to the system, the solar heat collector, solar seawater desalination, thermoelectric power generation, phase change heat storage and other technologies are combined, 24-hour continuous seawater desalination and thermoelectric power generation all day long can be achieved, power is supplied to the water pump through thermoelectric power generation, the energy consumption of the system is remarkably reduced, and flexible and full utilization of solar energy and low-cost and efficient desalination of seawater resources are achieved.

Description

Technical Field

[0001] The present invention relates to the technical fields of solar thermal utilization, solar seawater desalination, phase change heat storage, and thermoelectric power generation, and particularly relates to a seawater desalination system and a working method coupling a vacuum tube solar collector with phase change heat storage. Background Art

[0002] With the continuous growth of the world's population and the continuous reduction of existing fresh water reserves, the demand for fresh water resources has increased sharply. Approximately 98% of the water on the earth is in the ocean, so seawater desalination is an effective way to solve the current problem of short supply of fresh water resources. Solar distillation seawater desalination technology is one of the important methods to convert seawater into fresh water resources. Among them, active solar distillation seawater desalination technology preheats seawater by installing some collectors, including flat-plate solar collectors, vacuum tube solar collectors, solar concentrators, etc., to increase the seawater temperature, thereby increasing the seawater evaporation rate and ultimately achieving the purpose of increasing the fresh water output. However, traditional solar distillation seawater desalination technology cannot operate continuously due to the lack of sunlight at night, and there is a large amount of heat energy waste. Heat storage technology can store heat in different heat storage media, and when these heats are needed, the heat can be released and utilized at any time. Among many heat storage technologies, phase change heat storage technology has the characteristics of large heat storage density and stable phase change temperature, and can effectively solve the problems of instability and volatility in the utilization of renewable energy. Summary of the Invention

[0003] In order to overcome the deficiencies of the prior art, the purpose of the present invention is to provide a seawater desalination system and a working method coupling a vacuum tube solar collector with phase change heat storage, which combines the vacuum tube solar collector with traditional solar distillation seawater desalination technology, effectively increases the seawater evaporation rate and the fresh water output; by combining with phase change heat storage technology, not only the fresh water output is increased, but also the problem that seawater desalination cannot be carried out under the condition of no light at night is overcome; using a thermoelectric device for power generation can realize waste heat utilization and improve the comprehensive utilization rate of solar energy. This system can achieve continuous seawater desalination and thermoelectric power generation for 24 hours, and has the advantages of energy conservation, environmental protection, high fresh water output rate, and high energy utilization rate.

[0004] To achieve the above purpose, the present invention adopts the following technical solutions:

[0005] A seawater desalination system coupling a vacuum tube solar collector with phase change heat 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 fresh water collection tank 10, a second thermoelectric module 13, a second fresh water 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 water pumps; the water outlet of the vacuum tube solar collector 1 is connected to the seawater evaporation area 19 and a water tank of the seawater supply tank 3 respectively through a first three-way valve 2; the other water tank of the seawater supply tank 3 is connected to the water inlet of the vacuum tube solar collector 1 and the seawater evaporation area 19 respectively through a first water pump 6 after being connected to a second three-way valve 7; the water outlet at the lower part of the back side of the glass cover plate 8 is connected to the condensate channel 15 through the first fresh water collection tank 10, a third valve 11 and a second water pump 12; the water outlet at the lower part of the sunny side of the glass cover plate 8 is connected to the condensate channel 15 through the second fresh water collection tank 22, a fourth valve 21 and a third water pump 20; the bottom container 16 is connected to the glass cover plate 8 to form a cavity as a closed seawater desalination space, and at the same time plays a heat preservation role; a corrugated heat absorption plate 17 and a phase change material filling area 18 are arranged 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 absorption plate 17 and is used for loading phase change materials to store heat; the seawater evaporation area 19 is located above the corrugated heat absorption plate 17 and is the main area where seawater desalination occurs; the first thermoelectric module 9 is located above the back side of the glass cover plate 8, and its hot end is in close contact with the glass cover plate 8, and 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, and the fins 14 are located in the condensate channel 15 to exchange heat with the condensed fresh water through convection.

[0006] The vacuum tube solar collector 1 is placed with its sunny side facing down, the seawater inlet is located at the bottom of the vacuum tube solar collector 1, and the seawater outlet is located at the top of the vacuum tube solar collector 1, which plays a role in preheating seawater.

[0007] The seawater supply tank 3 is provided with a central detachable partition, two water inlets and one water outlet; the central detachable partition 4 divides the interior of the seawater supply tank 3 into two left and right water tanks; the seawater supply port 5 is located in the right water tank of the seawater supply tank 3, and 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 water outlet is located in the right water tank of the seawater supply tank 3.

[0008] The glass cover plate 8 is in a roof shape. The angle between the sunny side on the left of the glass cover plate 8 and the horizontal plane is 30°, and the angle between the shady side on the right and the horizontal plane is 45°, which serves to condense water vapor. Flow guiding devices are installed at the lower edges of the left and right side plates, which serve to collect condensed fresh water and stabilize the flow rate, and divert the condensed fresh water to the first fresh water collection tank 10 and the second fresh water collection tank 22 respectively.

[0009] The material of the fin 14 is aluminum or copper to achieve efficient heat dissipation.

[0010] The material of the corrugated heat absorption plate 17 is 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 cannot have backflow; the first water pump 6 is continuously turned on for 24 hours; the second water pump 12 and the third water pump 20 are turned on during the day under sunlight and turned off at night without 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; all three passages of the first three-way valve 2 are opened during the day under sunlight and all closed at night without sunlight; the second three-way valve 7 only closes the passage connected to the seawater evaporation area 19 side during the day under sunlight, and the other two passages are opened, and only closes the passage connected to the water inlet side of the vacuum tube solar collector 1 at night without sunlight, and the other two passages are opened; the third valve 11 and the fourth valve 21 are opened during the day under sunlight and closed at night without sunlight.

[0013] Working method of a seawater desalination system that couples a vacuum tube solar collector with phase change heat storage. During daylight hours, the second three-way valve 7 is opened to connect the two side passages to the lower water inlet of the vacuum tube solar collector 1 and the right water tank of the seawater supply tank 3. All passages of the first water pump 6 and the first three-way valve 2 are opened. Seawater first flows through the vacuum tube solar collector 1 from the right water tank of the seawater supply tank 3 for preheating. The preheated seawater is split 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 is used at night to increase the desalination rate at night. The other part directly flows into the seawater evaporation area 19 for desalination. Sunlight passes through the glass cover plate 8 and shines on the seawater surface and the corrugated heat absorption plate 17. The seawater absorbs solar energy and evaporates into water vapor. When the water vapor rises, it is condensed when it meets the glass cover plate 8. The corrugated heat absorption plate 17 transfers the absorbed heat to the phase change material filling area 18 for storage and is used at night. 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 and is used to supply power for the three water pumps. The fresh water condensed 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-mentioned 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 upper phase change material and the lower condensed water and supplies power for the opened water pumps. At the same time, the heated condensed water is led out from the condensate channel 15 to supply domestic water for residents.

[0014] During non-daylight hours at night, the second three-way valve 7 is opened to connect the two side passages to the right water tank of the seawater supply tank 3 and the seawater evaporation area 19. The first water pump 6 is opened, and all passages of the first three-way valve 2 are closed. The central partition 4 is removed so that part of the preheated seawater stored in the left water tank of the seawater supply tank 3 during the day can flow from the water outlet on the right water tank to the seawater evaporation area 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 used for seawater desalination. At the same time, the first thermoelectric module 9 generates electricity in the same way as in the daytime mode and supplies power for the first water pump 6. The fresh water collected in the first fresh water collection tank 10 and the second fresh water collection tank 22 is used for domestic water.

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

[0016] All the energy for desalinating seawater in the system of the present invention comes from solar energy, with high comprehensive utilization rate of solar energy, energy conservation and environmental protection.

[0017] The system of the present invention makes full use of water resources. Compared with directly using the produced fresh water for domestic water, the present invention first uses the produced condensed fresh water as the cold end of the thermoelectric module for thermoelectric power generation, and then uses it for domestic water, so that the waste heat of the condensed water can be fully utilized and the electricity cost of the system can be reduced.

[0018] The system of the present invention combines the solar distillation seawater desalination technology with the phase change heat storage technology, which not only improves the fresh water output, but also effectively solves the problem that seawater desalination cannot be carried out at night.

[0019] The system of the present invention combines the vacuum tube solar collector with the traditional solar distillation seawater desalination technology, effectively improving the seawater evaporation rate and increasing the fresh water output.

[0020] The system of the present invention applies the temperature difference between the inner and outer sides of the back side of the glass cover plate to the thermoelectric module for power generation, with high waste heat utilization rate and cost savings for seawater desalination. Brief Description of the Drawings

[0021] Figure 1 It is a schematic structural diagram of a seawater desalination system coupling a vacuum tube solar collector with phase change heat storage. Detailed Description of the Embodiment

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

[0023] Embodiment

[0024] Refer to Figure 1 , a seawater desalination system coupling a vacuum tube solar collector with phase change heat storage of the present invention includes a vacuum tube solar collector 1, a seawater supply tank 3, a glass cover plate 8, a first thermoelectric module 9, a first fresh water collection tank 10, a second thermoelectric module 13, a second fresh water collection tank 22, fins 14, a condensate water 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 will Figure 1 introduce in detail the connection relationship between each component:

[0026] The upper water outlet of the vacuum tube solar collector 1 is respectively connected to the seawater evaporation area 19 and the left water tank of the seawater supply tank 3 through the first three-way valve 2; the right water tank of the seawater supply tank 3 is divided into two paths after being connected to the second three-way valve 7 through the first water pump 6, and is respectively connected to the lower water inlet of the vacuum tube solar collector 1 and the seawater evaporation area 19; the lower water outlet on the sunny side of the left side of the glass cover plate 8 is connected to the condensate channel 15 through the second fresh water collection tank 22, the fourth valve 21 and the third water pump 20; the lower water outlet on the shaded side of the right side of the glass cover plate 8 is connected to the condensate channel 15 through the first fresh water 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 as a closed seawater desalination space, and at the same time plays a heat preservation role; a corrugated heat absorption plate 17 and a phase change material filling area 18 are arranged 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 absorption plate 17 and is used for loading phase change materials to store heat; the seawater evaporation area 19 is located above the corrugated heat absorption 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, and the cold end directly exchanges heat with the outside air through natural convection; the hot end of the second thermoelectric module 13 contacts the bottom of the phase change material filling area 18, and the cold end is provided with fins 14, and the fins 14 are located in the condensate channel 15 to exchange heat with the condensed fresh water through convection.

[0027] The system of the present invention is divided into two working modes: day and night, and their operating modes are as follows:

[0028] 1. Daytime operating mode

[0029] Open the two-way three-way valve 7 to connect the two sides of the lower water inlet of the vacuum tube solar collector 1 and the right water tank of the seawater supply tank 3, all the passages of the first water pump 6 and the first three-way valve 2. Seawater first flows through the vacuum tube solar collector 1 from the right water tank of the seawater supply tank 3 for preheating. After preheating, the seawater is split 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 is used at night to increase the desalination rate at night. The other part directly flows into the seawater evaporation area 19 for desalination. Sunlight passes through the glass cover plate 8 and irradiates onto the seawater surface and the corrugated heat absorption plate 17. After the seawater absorbs solar energy, water vapor evaporates. When the water vapor rises, it is condensed by the glass cover plate 8. After the corrugated heat absorption plate 17 absorbs heat, it transfers the heat to the phase change material filling area 18 for storage and is used at night. At the same time, the first thermoelectric module 9 generates electricity under the temperature difference between the shaded side on the right of the glass cover plate 8 and the environment, and is used to supply power for the water pump. The fresh water condensed 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-mentioned valves and water pumps to the condensed water 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 condensed water below, and supplies power for the opened water pumps. At the same time, the heated condensed water is led out from the condensed water channel 15 to supply domestic water for residents.

[0030] 2. Night operation mode

[0031] Open the two sides of the two-way three-way valve 7 connecting the right water tank of the seawater supply tank 3 and the seawater evaporation area 19 and the first water pump 6, close all the passages of the first three-way valve 2, and remove the central partition 4, so that part of the preheated seawater stored in the left water tank of the seawater supply tank 3 during the day can flow from the water outlet on the right water tank to the seawater evaporation area 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 used for seawater desalination. At the same time, the first thermoelectric module 9 generates electricity in the same way as in the daytime mode to supply power for the first water pump 6. The fresh water collected in the first fresh water collection tank 10 and the second fresh water collection tank 22 is used for domestic water.

Claims

1. A seawater desalination system with vacuum tube solar collector coupled with phase change heat storage, characterized in that: The system comprises a vacuum tube solar thermal 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 condensed water channel (15), a bottom container (16), a corrugated heat absorbing plate (17), a phase change material filling area (18), a seawater evaporation area (19), various valves and a water pump; the water outlet of the vacuum tube solar thermal collector (1) is divided into a first three-way valve (2) and a second three-way valve (2) to form a phase change material filling area (18), a seawater evaporation area (19), various valves and a water pump; The first water tank (10) is connected to the seawater evaporation zone (19) and a water tank of the seawater supply tank (3); 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 divided into two paths, which are respectively connected to the water inlet of the vacuum tube solar collector (1) and the seawater evaporation zone (19); the lower water outlet of the sun-facing side of the glass cover plate (8) is connected to the condensation water channel (15) through the first fresh water collection box (10), the third valve (11) and the second water pump (12); the lower water outlet of the sun-facing side of the glass cover plate (8) is connected to the condensation water channel (15) through the second fresh water collection box (11). The tank (22), the fourth valve (21) and the third water pump (20) are connected to the condensation water channel (15); the bottom container (16) is connected to the glass cover plate (8) to form a cavity as a closed seawater desalination space, and at the same time plays a role in heat preservation; a corrugated heat absorbing plate (17) and a phase change material filling area (18) are arranged in the cavity to divide the cavity into an upper seawater evaporation area (19) and a lower condensation water 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 area (18). The invention relates to a method for storing heat; the seawater evaporation zone (19) is located above the corrugated heat absorption plate (17) and is the main area where seawater desalination occurs; the first thermoelectric module (9) is located above the sun-proof side of the glass cover plate (8), and the hot end surface is tightly fitted with the glass cover plate (8), and the cold end directly exchanges heat with the outside air by natural convection; the hot end of the second thermoelectric module (13) is in contact with the bottom of the phase change material filling zone (18), and the cold end is provided with fins (14), and the fins (14) are located in the condensation water channel (15) and exchange heat with the condensed fresh water by convection.

2. The seawater desalination system of vacuum tube solar collector coupled with phase change heat storage according to claim 1, characterized in that: The vacuum tube solar thermal collector (1) is placed facing the sun, the seawater inlet is located at the bottom of the vacuum tube solar thermal collector (1), and the seawater outlet is located at the top of the vacuum tube solar thermal collector (1), so as to preheat the seawater.

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

4. The seawater desalination system of vacuum tube solar collector coupled with phase change heat storage according to claim 1, characterized in that: The glass cover plate (8) is in the shape of a roof, the angle between the left sun-facing side of the glass cover plate (8) and the horizontal plane is 30 degrees, and the angle between the right sun-facing side and the horizontal plane is 45 degrees, which plays a role in condensing water vapor; guide devices are installed at the lower edges of the left and right side plates, which play a role in collecting condensed fresh water and stabilizing the flow, and the condensed fresh water is respectively guided to the first fresh water collection box (10) and the second fresh water collection box (22).

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

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

7. The seawater desalination system of vacuum tube solar collector coupled with phase change heat 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 unable to reflux; the first water pump (6) is turned on for 24 hours continuously; the second water pump (12) and the third water pump (20) are turned on during the day when the light is on and turned off during the night when the light is not on.

8. The seawater desalination system of vacuum tube solar collector coupled with phase change heat 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 three passages of the first three-way valve (2) are all open during the daytime when the light is on, and are all closed during the nighttime when the light is not on; the second three-way valve (7) only closes the passage connected to the seawater evaporation zone (19) side during the daytime when the light is on, and the other two passages are open; during the nighttime when the light is not on, only closes the passage connected to the water inlet side of the vacuum tube solar collector (1), and the other two passages are open; the third valve (11) and the fourth valve (21) are open during the daytime when the light is on, and are closed during the nighttime when the light is not on.

9. The working method of a seawater desalination system of a vacuum tube solar collector coupled with phase change heat storage according to any one of claims 1 to 8, characterized in that: During the daytime, the second three-way valve (7) is opened to connect the water inlet at the lower end 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 entire passage of the first three-way valve (2). The seawater from the right water tank of the seawater supply tank (3) first flows through the vacuum tube solar collector (1) for preheating. The preheated seawater is 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 is used at night to increase the desalination rate at night. The other part directly flows into the seawater evaporation area (19) for desalination. Sunlight shines through the glass cover (8) onto the seawater surface and the corrugated heat absorbing plate (17). The seawater absorbs solar energy and evaporates water vapor. When the water vapor rises, it encounters the glass cover (8) and is condensed. The corrugated heat absorbing plate (17) absorbs the heat and transfers the heat to the seawater evaporation area (19). The first thermoelectric module (9) generates electricity under the action of the temperature difference between the sun-proof side of the glass cover plate (8) and the environment, and is used to supply electricity to the three water pumps. The fresh water condensed on the glass cover plate (8) flows to the first fresh water collection box (10) and the second fresh water collection box (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, and the condensed water flows to the condensed water channel (15) through the above valves and water pumps to cool the cold end of the second thermoelectric module (13). At this time, the second thermoelectric module (13) generates electricity under the action of the temperature difference between the upper phase change material and the lower condensed water, and supplies electricity to the opened water pumps. At the same time, the heated condensed water is drawn out from the condensed water channel (15) to supply domestic water to residents. During the non-lighting period at night, the second three-way valve (7) is opened to connect the two side passages of the right water tank of the seawater supply tank (3) and the seawater evaporation zone (19), the first water pump (6) is opened, all the passages of the first three-way valve (2) are closed, and the central partition (4) is removed, so that part 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. At the same time, the first thermoelectric module (9) generates electricity in the same way as in the daytime mode to supply electricity to the first water pump (6), and the fresh water collected by the first fresh water collection tank (10) and the second fresh water collection tank (22) is used for domestic water.

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