CN118517810A - Phase-change heat storage device and solar water heating system - Google Patents

Abstract

The invention relates to the technical field of heat storage devices, and particularly provides a phase-change heat storage device and a solar water heating system. Wherein, the shell is provided with an inlet and an outlet for the heat transfer working medium to enter and exit the shell. The rotating shaft is rotatably arranged in the shell, and the heat storage module comprises a shell and a heat storage working medium accommodated in the shell. In the process that the heat storage module rotates along with the rotating shaft, the heat storage working medium exchanges heat with the heat transfer working medium in the shell. The heat storage working medium comprises an inorganic hydrated salt phase change material, and phase change occurs in the process of heat exchange with the heat transfer working medium so as to store heat in the heat storage working medium. The solar water heating system comprises a solar heat collector, at least one phase-change heat storage device and a user side. The phase change heat storage device is configured to exchange heat with a heat transfer medium from the solar collector. The user side is configured to pump tap water to the phase-change heat storage device, exchange heat with the heat storage working medium and then convey the tap water to the user.

Description

Phase change heat storage device and solar water heating system

Technical Field

At least one embodiment of the present invention relates to the technical field of heat storage devices, and more specifically, to a phase change heat storage device and a solar water heating system.

Background Art

With the continuous growth of energy consumption, the use of renewable energy and energy conservation and emission reduction have become a hot topic. Among renewable energy sources, solar energy, as a clean and renewable energy, has a wide range of application prospects. Among them, solar water heating system is a very typical application.

Solar energy has a low energy density and is intermittent and volatile. It needs to be converted into thermal energy and stored for subsequent use. At present, latent heat storage technology is widely used. Its main principle is that the material absorbs or releases heat during the phase change process to store heat in the material or release it from the material. Phase change materials have the characteristics of good thermal conductivity, large heat absorption and release, and small temperature change during phase change. For example, inorganic hydrated salt materials are commonly used in solar water heating systems.

In the related art, phase change heat storage devices usually encapsulate phase change materials in spherical shells, and then densely arrange multiple such spherical shells to exchange heat when water flows through these spheres. However, under natural convection, the heat exchange effect is still not ideal. In addition, when the inorganic hydrated salt material is near the phase change temperature, the solubility changes, resulting in phase separation, which affects the heat exchange. Therefore, how to further improve the heat exchange performance of the phase change heat storage device has become a technical problem that needs to be solved urgently.

Summary of the invention

In view of the above problems, the present invention provides a phase change heat storage device and a solar water heating system, which can enhance convective heat transfer, reduce the possibility of phase separation, and improve heat exchange performance.

In order to achieve the above-mentioned purpose, the present invention provides a phase change heat storage device, comprising: a shell, an inlet and an outlet are formed on the shell for a heat transfer medium to enter and exit the shell; a rotating shaft rotatably installed in the shell; a heat storage module, arranged on the rotating shaft, the heat storage module comprises a shell and a heat storage medium accommodated in the shell, wherein, when the heat storage module rotates with the rotating shaft, the heat storage medium exchanges heat with the heat transfer medium in the shell; wherein the heat storage medium comprises an inorganic hydrated salt phase change material, which undergoes a phase change in response to the heat exchange process with the heat transfer medium, so as to store heat in the heat storage medium.

In an illustrative embodiment, at least one of the heat storage modules is provided and is spaced apart on the rotating shaft along a circumferential direction.

In an illustrative embodiment, the heat storage module comprises: a plurality of heat storage units, the plurality of heat storage units are configured to be arranged in rows and/or columns, each of the heat storage units is filled with a heat storage medium; a plurality of trusses, the trusses are configured to be hollow tubular rods, arranged between two adjacent heat storage units to connect the adjacent heat storage units, so that the heat storage medium flows between the adjacent heat storage units.

In an illustrative embodiment, it further includes a diffuser plate, which is arranged between the above-mentioned inlet and the above-mentioned rotating shaft; the above-mentioned diffuser plate is provided with a plurality of through holes, so that the heat transfer medium from the above-mentioned inlet can be dispersed through the above-mentioned through holes of the above-mentioned diffuser plate and then flow to the above-mentioned heat storage module.

In an illustrative embodiment, the axis of the inlet and the axis of the outlet are collinear and both are perpendicular to the axis of the rotating shaft.

In an illustrative embodiment, the inlet and the outlet are arranged on the same straight line along the vertical direction.

In an illustrative embodiment, the shell is configured as a hollow spherical shell.

The present invention also provides a solar water heating system, comprising: a solar collector, suitable for converting solar energy into thermal energy and heating a heat transfer medium; at least one phase change heat storage device as in any of the above embodiments, configured to exchange heat with the heat transfer medium from the above solar collector to store heat in the heat storage medium; a user end, configured to pump tap water to the above phase change heat storage device, exchange heat with the above heat storage medium and then transport it to the user.

In an illustrative embodiment, a heat storage tank is further included, which is configured to receive and store the heat transfer medium from the phase change heat storage device and the solar collector, and to use the heat transfer medium to exchange heat with the tap water pumped from the user end.

In an illustrative embodiment, three of the above-mentioned phase change heat storage devices are arranged in sequence, wherein the inlet of the first phase change heat storage device is connected to the above-mentioned solar thermal collector, the inlet of the second phase change heat storage device is connected to the outlet of the first phase change heat storage device, the inlet of the third phase change heat storage device is connected to the outlet of the second phase change heat storage device, and the outlet of the third phase change heat storage device is connected to the above-mentioned solar thermal collector and the above-mentioned user end, respectively.

In an illustrative embodiment, the phase change temperature range of the heat storage medium of the first phase change heat storage device is t1~t2, the phase change temperature range of the heat storage medium of the second phase change heat storage device is t2~t3, the phase change temperature range of the heat storage medium of the third phase change heat storage device is t3~t4, and t1-t2=t2-t3=t3-t4.

The thermal phase change heat storage device and solar water heating system provided by the present invention change the flow state of the heat transfer medium when flowing through the shell, strengthen the convective heat transfer, and improve the heat exchange effect by arranging a heat storage module that rotates with the rotating shaft in the shell. The heat storage medium in the heat storage module includes an inorganic hydrated salt phase change material, which has a strong heat storage capacity and low cost. In addition, since the heat storage module rotates with the rotating shaft, the possibility of phase separation of the material is reduced, and the heat exchange performance is further improved. In the solar water heating system, the heat transfer medium heated by the solar collector is exchanged with the phase change heat storage device to convert solar energy into thermal energy for storage, thereby compensating for the disadvantage of the volatility of solar energy.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

FIG1 is a three-dimensional structural diagram of a phase change heat storage device provided by the present invention;

FIG2 is a schematic plan view of the heat storage module 3 in the exemplary embodiment shown in FIG1 ;

FIG3 is a schematic plan view of the diffuser plate 4 in the exemplary embodiment shown in FIG1 ;

FIG4 is a schematic diagram of a solar water heating system provided by the present invention;

FIG5 is a diagram showing an arrangement of multiple phase change heat storage devices in the exemplary embodiment shown in FIG4 ;

FIG. 6 is a schematic diagram of a solar water heating system in another exemplary embodiment.

In the above drawings, the meanings of the reference numerals are as follows:

1. Shell;

11. Import;

12. Export;

2. Rotating shaft;

3. Heat storage module;

31. Heat storage unit;

32. Truss;

4. Diffuser plate;

5. Solar collector;

6. Phase change heat storage device;

61. A first phase change heat storage device;

62. A second phase change heat storage device;

63. The third phase change heat storage device;

7. Heat storage tank.

DETAILED DESCRIPTION

In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. The terms used herein are only for describing specific embodiments and are not intended to limit the present invention.

The terms "include", "comprising", etc. used herein indicate the presence of the features, steps, operations and/or components, but do not exclude the presence or addition of one or more other features, steps, operations or components. All terms used herein, including technical and scientific terms, have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

In this document, unless otherwise specified, directional terms such as "upper", "lower", "left", "right", "inner", "outer", etc. are used to indicate the orientation or positional relationship based on the drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device, element or component referred to must have a specific orientation, be constructed or operate in a specific orientation. It should be understood that when the absolute position of the described object changes, the relative positional relationship they represent may also change accordingly. Therefore, these directional terms should not be understood as limiting the present invention.

When using expressions such as "at least one of A, B, and C, etc.", it should generally be interpreted as the meaning of the expression generally understood by those skilled in the art. For example, "a system having at least one of A, B, and C" should include but not be limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and/or A, B, C, etc. When using expressions such as "at least one of A, B, or C, etc.", it should generally be interpreted as the meaning of the expression generally understood by those skilled in the art. For example, "a system having at least one of A, B, or C" should include but not be limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and/or A, B, C, etc.

It will be appreciated by those skilled in the art that the features described in the various embodiments and/or claims of the present invention may be combined and/or combined in various ways, even if such combinations and/or combinations are not explicitly described in the present invention. In particular, the features described in the various embodiments and/or claims of the present invention may be combined and/or combined in various ways without departing from the spirit and teachings of the present invention. All of these combinations and/or combinations fall within the scope of the present invention.

FIG1 is a three-dimensional structural diagram of a phase change heat storage device provided by the present invention.

An exemplary embodiment of the present invention provides a phase change heat storage device, as shown in FIG1 , comprising a shell 1, a rotating shaft 2 and a heat storage module 3. The shell 1 is formed with an inlet 11 and an outlet 12 for the heat transfer medium to enter and exit the shell 1. The rotating shaft 2 is rotatably installed in the shell 1, and the heat storage module 3 is arranged on the rotating shaft 2. The heat storage module 3 includes an outer shell and a heat storage medium accommodated in the outer shell. In the process of the heat storage module 3 rotating with the rotating shaft 2, the heat storage medium exchanges heat with the heat transfer medium in the shell 1. The heat storage medium includes an inorganic hydrated salt phase change material, which undergoes a phase change in response to the heat exchange process with the heat transfer medium to store heat in the heat storage medium.

In such an embodiment, a cavity is formed in the shell 1, and the heat transfer medium enters the cavity of the shell 1 from the inlet 11 and flows out of the shell 1 from the outlet 12. In the cavity of the shell 1, the heat storage module 3 is arranged on the rotating shaft 2 and rotates with the rotating shaft 2, thereby changing the flow state of the heat transfer medium in the shell 1, strengthening the convective heat transfer, and improving the heat exchange effect. The use of inorganic hydrated salt phase change material as the heat storage medium in the heat storage module 3 not only has a strong heat storage capacity, but also because the heat storage module 3 rotates with the rotating shaft 2, it is not easy to separate phases, further improving the heat exchange performance.

In the embodiment of the present disclosure, the rotating shaft 2 is installed on the housing 1 through a bearing, and is connected to the driving shaft of the motor and is driven to rotate by the motor.

In the embodiments of the present disclosure, the phase change temperature range of the inorganic hydrated salt phase change material is 45°C to 60°C.

In an exemplary embodiment, the shell 1 is constructed as a hollow spherical shell. Since the rotating shaft 2 drives the heat storage module 3 to rotate inside the shell 1, the spherical shell can improve space utilization, and the surface area of the spherical shell is smaller than the surface area of other shells (such as cubic shells), which can reduce heat loss during heat exchange.

FIG. 2 is a schematic plan view of the heat storage module 3 in the exemplary embodiment shown in FIG. 1 .

In an exemplary embodiment, as shown in FIG2 , at least one heat storage module 3 is provided, and is spaced apart on the rotating shaft 2 along the circumferential direction. As shown in FIG1 , eight heat storage modules 3 are provided, and are spaced apart along the circumferential direction. Further, a plurality of heat storage modules 3 located on the same circumferential surface constitute a heat storage module, and a plurality of heat storage modules are spaced apart in the axial direction to increase the coverage of the heat storage module 3 and improve the heat exchange effect.

According to an embodiment of the present disclosure, the heat storage module 3 includes a plurality of heat storage units 31 and a plurality of trusses 32, wherein the plurality of heat storage units 31 are configured to be arranged in rows and/or columns, and each heat storage unit 31 is filled with a heat storage medium. The trusses 32 are configured as hollow tubular rods, and are arranged between two adjacent heat storage units 31 to connect the adjacent heat storage units 31, so that the heat storage medium flows between the adjacent heat storage units 31.

Exemplarily, as shown in FIG. 2 , a plurality of heat storage units 31 are arranged in a rectangular array of 8 rows and 4 columns. In the array, a truss 32 is connected between every two adjacent heat storage units 31 , and two trusses 32 arranged in an X-shape are connected to each other.

In some other embodiments, the heat storage unit 31 is also constructed as a spherical shell, which makes it easy to increase the heat exchange area with the heat transfer fluid, and the connection between the spherical shell and the truss 32 is convenient for increasing the complexity of the system structure during arrangement, improving space utilization and helping to enhance convective heat transfer.

More specifically, the heat storage unit 31 and the truss 32 are both made of plastics that are resistant to high temperatures and corrosion and have excellent mechanical properties, including but not limited to polyetheretherketone, polyimide, and the like.

FIG. 3 is a schematic plan view of the diffuser plate 4 in the exemplary embodiment shown in FIG. 1 .

In an exemplary embodiment, as shown in FIG3 , the phase change heat storage device further includes a diffuser plate 4 disposed between the inlet 11 and the rotating shaft 12. The diffuser plate 4 is provided with a plurality of through holes, so that the heat transfer medium from the inlet 11 flows to the heat storage module 3 through the through hole dispersion ports of the diffuser plate 4.

In such an embodiment, the diffuser plate 4 is disposed in the housing 1 by clamping or integrally forming, and the distance between the diffuser plate 4 and the rotating shaft 12 is greater than the maximum length dimension of the heat storage module 3, so as to avoid affecting the heat storage module 3 from rotating with the rotating shaft 2. The horizontal plane where the diffuser plate 4 is located is perpendicular to the axis of the inlet 11. When the heat transfer medium enters the housing 1 from the inlet 11, it will first impact the surface of the diffuser plate 4, diffuse along the surface of the diffuser plate 4, and then flow along the through holes on the diffuser plate 4 to the heat storage module 3, so that the heat transfer medium can be distributed more evenly in the housing 1, and the convective heat transfer can be further enhanced.

According to an embodiment of the present disclosure, the axis of the inlet 11 is colinear with the axis of the outlet 12 , and both are perpendicular to the axis of the rotating shaft 2 .

More specifically, the inlet 11 and the outlet 12 are arranged on the same straight line along the vertical direction.

In such an embodiment, the inlet 11 and the outlet 12 are arranged in a colinear manner and in a vertical direction, so that the heat transfer medium entering the shell 1 can flow under the action of gravity and impact the heat storage module 3 after passing through the diffuser 4, so that the heat storage module 3 plays a certain auxiliary role in the rotation of the rotating shaft 2, thereby reducing the load of the motor drive.

FIG. 4 is a schematic diagram of a solar water heating system provided by the present invention.

An exemplary embodiment of the present invention further provides a solar water heating system, comprising a solar collector 5, at least one phase change heat storage device 6 as in any of the above embodiments, and a user end. The solar collector 5 is suitable for converting solar energy into thermal energy and heating a heat transfer medium. The phase change heat storage device 6 is configured to exchange heat with the heat transfer medium from the solar collector 5 to store heat in the heat storage medium. The user end is configured to pump tap water to the phase change heat storage device 6, exchange heat with the heat storage medium, and then deliver it to the user.

In such an embodiment, the heat transfer medium is water. After the solar collector 5 heats the water, it is transported to the inlet 11 of the phase change heat storage device 6, and heat is exchanged with the heat storage medium in the phase change heat storage device 6 to store the heat in the heat storage medium. The water after the temperature drops flows out from the outlet 12 and flows back to the solar collector 5 to continue heating. In this process, the user end pumps the lower temperature tap water to the phase change heat storage device 6 for heat exchange, absorbs the pre-stored heat, and transports the hot water to the user, which can solve the problem of unstable hot water supply at night or when the sun is insufficient. It should be noted that during the heat storage process, if the user needs hot water, the tap water is pumped to the auxiliary heating device for heating. After the heat storage is completed, heat is taken from the phase change heat storage device 6.

According to an embodiment of the present disclosure, the solar water heating system further comprises a heat storage tank 7, which is configured to receive and store heat transfer medium from the phase change heat storage device 6 and the solar collector 5, and to exchange heat with tap water pumped from the user end using the heat transfer medium.

4 , wherein the outlet end of the solar collector 5 is connected to the A1 port of the first three-way valve, the A2 port of the first three-way valve is connected to the inlet 11 of the phase change heat storage device 6, and the A3 port is connected to the hot water storage tank 7; the outlet 12 of the phase change heat storage device 6 is connected to the B2 port of the second three-way valve, the hot water storage tank 7 is also connected to the B3 port of the second three-way valve, and the B1 port of the second three-way valve is connected to the solar collector 5.

When storing heat, the solar collector 5 transfers the hot water phase change heat storage device 6 and the hot water storage tank 7 through the first three-way valve, and the cold water after heat exchange with the phase change heat storage device 6 flows back to the solar collector 5 through the second three-way valve, and the hot water storage tank 7 temporarily stores the hot water. When the user needs hot water, the tap water is first pumped to the hot water storage tank 7 for heat exchange. If the demand cannot be met, the auxiliary heating device is activated for heating. After the heat storage is completed, the water in the hot water storage tank 7 can be pumped to the phase change heat storage device 6 for heat extraction, or flow back to the solar collector 5.

FIG. 5 is a diagram showing an arrangement of multiple phase change heat storage devices in the exemplary embodiment shown in FIG. 4 .

In an exemplary embodiment, three phase change heat storage devices 6 are arranged in sequence, wherein the inlet 11 of the first phase change heat storage device 61 is connected to the solar collector 5, the inlet 11 of the second phase change heat storage device 62 is connected to the outlet 12 of the first phase change heat storage device 61, the inlet 11 of the third phase change heat storage device 63 is connected to the outlet 12 of the second phase change heat storage device 62, and the outlet of the third phase change heat storage device 63 is connected to the solar collector 5 and the user end respectively.

In such an embodiment, by increasing the number of phase change heat storage devices, the heat exchange stroke and time of the heat transfer medium are extended, making the heat exchange more sufficient.

According to an embodiment of the present disclosure, the phase change temperature range of the heat storage medium of the first phase change heat storage device 61 is t1~t2, the phase change temperature range of the heat storage medium of the second phase change heat storage device 62 is t2~t3, the phase change temperature range of the heat storage medium of the third phase change heat storage device 63 is t3~t4, and t1-t2=t2-t3=t3-t4.

Exemplarily, t1=60°C, t2=55°C, t3=50°C, t4=45°C, so that the phase change temperature range is arranged in steps, so that a high heat exchange efficiency can be maintained during heat storage (heat transfer medium flows from inlet 11 to outlet 12) and heat extraction (heat transfer medium flows from outlet 12 to inlet 11).

According to an embodiment of the present disclosure, the first phase change heat storage device 61, the second phase change heat storage device 62 and the third phase change heat storage device 63 are arranged in sequence in the horizontal direction, that is, the axes of the inlet 11 and the outlet 12 extend in the horizontal direction. When storing heat, the heat transfer medium flows from the first phase change heat storage device 61 to the third phase change heat storage device 63, so that the temperature of the heat transfer medium decreases while adapting to the phase change temperature range. When taking out heat, the heat transfer medium flows from the third phase change heat storage device 63 to the first phase change device 61, so that the temperature of the heat transfer medium increases while adapting to the phase change temperature range. In the process of heat storage and heat taking, the water pump and the drive motor of the rotating shaft 2 provide the power for the flow of the heat transfer medium. When switching the heat storage/heat taking mode, that is, when the flow direction changes, the corresponding control drive motor is reversed so that the system can operate smoothly and stably.

It should be noted that the first phase change heat storage device 61, the second phase change heat storage device 62 and the third phase change heat storage device 63 can also be arranged in sequence in the vertical direction, and the flow of the heat transfer medium under the action of gravity can reduce the load of the drive motor.

FIG. 6 is a schematic diagram of a solar water heating system in another exemplary embodiment.

In some other embodiments, as shown in FIG. 6 , the solar water heating system further includes valves a to e. When valves b, c, and e are opened and valves a and e are closed, hot water from the solar collector 5 flows through port A2, the phase change heat storage device 6, valves b, c, and e, the water storage tank 7, and port B3 in sequence, and then flows back to the solar collector 5. This working mode is usually suitable for when the sunlight is sufficient, the hot water output by the solar collector 5 is at a high temperature, or the hot water can be continuously output for a long time. The hot water is first sent to the phase change heat storage device 6 for heat exchange. When the heat exchange is not sufficient or the phase change heat storage device 6 has reached the upper limit of the heat storage, the excess hot water flows to the water storage tank 7 for storage. When valves a, c, and e are opened and valves b and d are closed, the hot water from the solar collector 5 flows through port A3, the hot water storage tank 7, valves e, c, a, the phase change heat storage device 6, and port B2 in sequence and then flows back to the solar collector 5. In this working mode, the hot water output by the solar collector 5 is first sent to the hot water storage tank 7 for storage to give priority to meeting the hot water demand of the user end. The water discharged from the hot water storage tank 7 flows to the phase change heat storage device 6, and the cold water after heat exchange flows back to the solar collector 5.

Furthermore, based on any of the above-mentioned embodiments, a water pump is provided upstream of the solar collector 5. When the difference between the outlet temperature and the inlet temperature of the solar collector 5 is equal to or higher than a preset value, the water pump will be turned on to pump the heat transfer medium or cold water with a lower temperature back to the solar collector 5. In the present embodiment, the preset value is 6°C.

The embodiments of the present invention are described above. However, these embodiments are only for the purpose of illustration, and are not intended to limit the scope of the present invention. Although the embodiments are described above, this does not mean that the measures in the various embodiments cannot be used in combination. The scope of the present invention is defined by the appended claims and their equivalents. Without departing from the scope of the present invention, those skilled in the art may make various substitutions and modifications, which should all fall within the scope of the present invention.

Claims (10)

1. A phase change heat storage device, comprising:

the heat transfer device comprises a shell (1), wherein an inlet (11) and an outlet (12) are formed on the shell (1) for heat transfer working media to enter and exit the shell (1);

The rotating shaft (2) is rotatably arranged in the shell (1);

the heat storage module (3) is arranged on the rotating shaft (2), and the heat storage module (3) comprises a shell and a heat storage working medium accommodated in the shell, wherein the heat storage working medium exchanges heat with the heat transfer working medium in the shell (1) in the process that the heat storage module (3) rotates along with the rotating shaft (2);

the heat storage working medium comprises an inorganic hydrated salt phase change material, and phase change occurs in the process of heat exchange with the heat transfer working medium so as to store heat in the heat storage working medium.

2. Phase change heat storage device according to claim 1, characterized in that the heat storage modules (3) are provided at least one and are arranged on the rotating shaft (2) at intervals in the circumferential direction.

3. Phase change heat storage device according to claim 2, characterized in that the heat storage module (3) comprises:

The heat storage units (31) are configured to be arranged at intervals along rows and/or columns, and each heat storage unit (31) is filled with a heat storage working medium;

-a plurality of trusses (32), the trusses (32) being configured as hollow tubular bars arranged between two adjacent heat storage units (31) to communicate adjacent heat storage units (31) such that the heat storage medium flows between adjacent heat storage units (31).

4. The phase change heat storage device according to claim 1, further comprising a diffuser plate (4) arranged between the inlet (11) and the rotating shaft (2);

The heat storage module is characterized in that the heat dissipation plate (4) is provided with a plurality of through holes so that heat transfer working medium from the inlet (11) flows onto the heat storage module (3) after being dispersed through the through holes of the heat dissipation plate (4).

5. Phase change heat storage device according to claim 4, characterized in that the axis of the inlet (11) and the axis of the outlet (12) are collinear and perpendicular to the axis of the rotating shaft (2).

6. Phase change heat storage device according to claim 1, characterized in that the housing (1) is configured as a hollow spherical housing.

7. A solar water heating system, comprising:

The solar heat collector (5) is suitable for converting solar energy into heat energy and heating a heat transfer working medium;

At least one phase change heat storage device (6) according to any one of claims 1-6 configured to exchange heat with a heat transfer medium from the solar collector (5) to store heat in a heat storage medium;

the user side is configured to pump tap water to the phase-change heat storage device (6), exchange heat with the heat storage working medium and then convey the heat to the user.

8. Solar water heating system according to claim 7, further comprising a heat storage tank (7) configured to receive and store heat transfer medium from the phase change heat storage device (6) and the solar collector (5), and to exchange heat with tap water pumped by the user side using the heat transfer medium.

9. Solar water heating system according to claim 7, characterized in that the phase change heat storage means (6) are arranged in sequence with three, wherein,

The inlet (11) of the first phase-change heat storage device (61) is connected with the solar heat collector (5), the inlet (11) of the second phase-change heat storage device (62) is connected with the outlet (12) of the first phase-change heat storage device (61), the inlet (11) of the third phase-change heat storage device (63) is connected with the outlet (12) of the second phase-change heat storage device (62), and the outlet of the third phase-change heat storage device (63) is connected with the solar heat collector (5) and the user side respectively.

10. Solar water heating system according to claim 9, characterized in that the phase change temperature range of the heat storage working medium of the first phase change heat storage device (61) is t1-t2, the phase change temperature range of the heat storage working medium of the second phase change heat storage device (62) is t2-t3, the phase change temperature range of the heat storage working medium of the third phase change heat storage device (63) is t3-t4, and t1-t2 = t2-t3 = t3-t4.