Solar energy cascade utilization electric-heat steam combined supply system and method

Abstract

The present application belongs to the technical field of solar energy utilization, and relates to a solar energy stepwise utilization electric-heat-steam combined supply system and method. The system comprises a first hot water supply subsystem, a heat exchange subsystem, a second hot water supply subsystem, a steam supply power generation subsystem and a photovoltaic power generation subsystem. The photovoltaic power generation subsystem is connected with the first hot water supply subsystem, the heat exchange subsystem, the second hot water supply subsystem and the steam supply power generation subsystem respectively. The present application can stepwise utilize solar energy, can provide hot water with high, medium and low temperatures by using solar energy gradient, can provide steam with high, medium and low parameters by using solar energy gradient, and can generate power by using the generated steam, so that solar energy is fully utilized, and the system has low investment and low cost. When sunlight is insufficient, standby equipment is arranged in each subsystem to ensure the supply of hot water and steam with various temperatures and parameters, and to ensure the normal operation of the system.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of solar energy utilization, and particularly relates to a solar energy cascade utilization electric-heat-steam combined supply system and method. BACKGROUND

[0002] The massive use and overexploitation of coal and oil have caused serious environmental pollution and energy shortage. Environmental pollution and energy crisis have seriously threatened human survival and development, so how to utilize solar energy and efficiently utilize solar energy has become a research topic.

[0003] There are currently some researches on the utilization of solar energy, such as Chinese Patent No. CN202010221321.X, which discloses a solar air source heat pump triple supply system and use method, which comprises an air source heat pump mechanism, a solar heat collecting mechanism, a first heat exchanger and a second heat exchanger. The air source heat pump mechanism comprises a compressor, a four-way reversing valve, an indoor air-cooled heat exchanger, a drying pipe, a throttling device and an outdoor air-cooled heat exchanger. The solar heat collecting mechanism comprises a low-temperature water tank, a first valve, a high-temperature constant temperature water tank, a solar heat collecting plate, a second valve, a third water pump and a fourth water pump. The low-temperature water tank is connected with the inner cavity of the first heat exchanger through the second water pump, and the high-temperature constant temperature water tank is connected with the inner cavity of the second heat exchanger through the first water pump. The triple supply system in the patent utilizes solar energy to realize the triple supply of heating, cooling and domestic hot water, but the triple supply system in the patent cannot supply hot water of different temperatures and steam of different parameters, and cannot generate electricity, so the solar energy is not efficiently utilized in cascade. SUMMARY

[0004] In view of the above problems in the prior art, the present application provides an electric-heat-steam combined supply system and method for solar energy cascade utilization, which can supply hot water of different temperatures and steam of different parameters, can generate electricity, and can efficiently utilize solar energy in cascade.

[0005] The present application adopts the following technical solutions:

[0006] An electric-heat-steam combined supply system for solar energy cascade utilization comprises a first hot water supply subsystem, a heat exchange subsystem, a second hot water supply subsystem, a steam supply and power generation subsystem and a photovoltaic power generation subsystem, wherein the photovoltaic power generation subsystem is connected with the first hot water supply subsystem, the heat exchange subsystem, the second hot water supply subsystem and the steam supply and power generation subsystem respectively.

[0007] The first hot water supply subsystem comprises a water source supply module, a solar heat collector and a low-temperature hot water storage module and a medium-temperature hot water storage module.

[0008] The solar energy collector comprises a pipeline-connected solar primary heating sub-module, a solar secondary heating sub-module, a water supply module, and a low-temperature hot water storage module.

[0009] The heat exchange subsystem comprises a concentrated solar collector, a molten salt storage tank, and a heat exchanger.

[0010] The steam supply and power generation subsystem comprises a steam generator and a back pressure turbine connected with each other.

[0011] As a preferred solution, the photovoltaic power generation subsystem comprises a photovoltaic power generation module, an energy storage module, and a power transmission module connected in sequence.

[0012] As a preferred solution, the power transmission module is further connected with an external power consumption module.

[0013] As a preferred solution, the connection pipeline between the water supply module and the solar primary heating sub-module is branched into an output pipeline and an input pipeline.

[0014] As a preferred solution, the solar secondary heating sub-module is connected with a first inlet pipeline of a thermal deaerator, an outlet of the thermal deaerator is connected with an inlet pipeline of the heat exchange end of the heat exchanger, and a second inlet of the thermal deaerator is connected with the low-pressure steam output pipeline.

[0015] As a preferred solution, the heat exchange subsystem further comprises an electrode-type molten salt boiler.

[0016] As a preferred solution, the heat exchange end of the heat exchanger is further connected with the electric steam boiler pipeline, the electric steam boiler is further connected with the high-pressure steam output pipeline, and the electric steam boiler is further connected with the photovoltaic power generation system and the generator.

[0017] As a preferred solution, the low-temperature hot water storage module comprises a connected low-temperature hot water storage tank and a low-temperature hot water output pipeline, and a low-temperature water supply pump is arranged on the low-temperature hot water output pipeline, and the low-temperature water supply pump is connected with the photovoltaic power generation system and the generator.

[0018] The medium-temperature hot water storage module comprises a connected medium-temperature hot water storage tank and a medium-temperature hot water output pipeline, and a medium-temperature water supply pump is arranged on the medium-temperature hot water output pipeline, and the medium-temperature water supply pump is connected with the photovoltaic power generation system and the generator.

[0019] The high-temperature hot water storage module comprises a connected high-temperature hot water storage tank and a high-temperature hot water output pipeline, and a high-temperature water supply pump is arranged on the high-temperature hot water output pipeline, and the high-temperature water supply pump is connected with the photovoltaic power generation system and the generator.

[0020] A solar energy cascade utilization electric-thermal steam combined supply method is also provided, which is based on the above-mentioned solar energy cascade utilization electric-thermal steam combined supply system and comprises the following steps:

[0021] S1. The water source supply module supplies water source to the solar primary heating submodule in the solar collector for preliminary heating to obtain low-temperature hot water.

[0022] S2. Part of the low-temperature hot water is transported to the low-temperature hot water storage module for storage, and the remaining low-temperature hot water is transported to the solar secondary heating submodule for further heating to obtain medium-temperature hot water.

[0023] S3. Part of the medium-temperature hot water is transported to the medium-temperature hot water storage module for storage, and the remaining medium-temperature hot water is transported to the heat exchanger in the heat exchange subsystem and exchanges heat with the molten salt heated by the concentrated solar collector to obtain high-temperature hot water.

[0024] S4. Part of the high-temperature hot water is transported to the high-temperature hot water storage module for storage, and the remaining high-temperature hot water is transported to the steam generator for evaporation to obtain high-parameter steam.

[0025] S5. Part of the high-parameter steam is output through the high-parameter steam output pipeline, and the remaining high-parameter steam is transported to the back pressure steam turbine, the body air outlet of the back pressure steam turbine outputs medium-parameter steam through the medium-parameter steam output pipeline, the steam turbine outlet of the back pressure steam turbine outputs low-parameter steam through the low-parameter steam output pipeline, and the back pressure steam turbine outputs steam while driving the generator to generate electricity.

[0026] As a preferred solution, in step S3, the remaining medium-temperature hot water is subjected to thermal deaeration in a thermal deaerator before being delivered to the heat exchanger in the heat exchange subsystem, and the thermal deaerator is supplied with heat from the low-parameter steam output from the steam turbine outlet of the back-pressure steam turbine through a low-parameter steam output pipeline.

[0027] The present application has the following advantages:

[0028] The present application can utilize solar energy in stages, can provide high, medium and low temperature hot water using solar energy gradient, can provide high, medium and low parameter steam using solar energy gradient, and can generate electricity using the generated steam, thereby fully utilizing solar energy.

[0029] The water is preliminarily heated by the solar primary heating sub-module in the solar collector, thereby obtaining low-temperature hot water, and the low-temperature hot water is further heated by the solar secondary heating sub-module in the solar collector, thereby obtaining medium-temperature hot water. Since the solar collector has a temperature limit for heating water, a heat exchange subsystem is provided in the present application, the molten salt is heated by the concentrated solar collector, and the medium-temperature hot water is subjected to heat transfer by the heated molten salt, thereby further increasing the water temperature. Moreover, the operation cost of the concentrated solar collector is higher than that of the solar collector, so in the present application, the heating of the low-temperature hot water and the medium-temperature hot water is performed by the solar collector, and the concentrated solar collector only performs the heating of the high-temperature hot water, thereby reducing the operation cost of the system.

[0030] The present application can produce high, medium and low parameter steam by the steam generator and the back-pressure steam turbine, and the medium and low parameter steam can be output through the body air outlet and the steam turbine outlet of the back-pressure steam turbine itself, and the back-pressure steam turbine can directly drive the generator to generate electricity while producing medium and low parameter steam, thereby truly realizing the full and step-by-step utilization of energy, and reducing the investment and cost of the system.

[0031] The photovoltaic power generation system in the present application comprises a photovoltaic power generation module, an energy storage module and a power transmission module connected in sequence, the power transmission module is connected with an external power consumption module, and the power transmission module is also connected with an external power acquisition module. That is, the photovoltaic power generation system in the present application can store the electric energy generated by photovoltaic power generation in the energy storage module for standby use, can also output to the external power consumption module for use, and can also acquire power through the external power acquisition module when the electric energy in the combined supply system is insufficient.

[0032] The low-temperature heat pump is provided in the present application, and when the sunlight is insufficient, the opening and closing of the first valve, the second valve and the third valve are controlled to make the low-temperature heat pump serve as a standby heat source to heat the water. Since the low-temperature heat pump is connected with the photovoltaic power generation system, the low-temperature heat pump can work at any time by using the electric energy stored in the energy storage module or the off-peak electricity acquired from the external power acquisition module, thereby ensuring the normal operation of the system.

[0033] The heat exchanger subsystem in the application is provided with a thermal deaerator to remove oxygen in hot water, which lays a foundation for subsequent steam production and power generation. Moreover, the heat source of the thermal deaerator is low-parameter steam output by the back pressure turbine, so as to realize more sufficient utilization of energy.

[0034] The heat exchanger subsystem in the application is provided with an electrode type molten salt boiler, which is connected with the molten salt storage tank through a pipeline, and is connected with the photovoltaic power generation subsystem and the generator. Therefore, the electrode type molten salt boiler can also be used as a backup heat source to heat the molten salt when sunlight is not sufficient enough, so as to ensure normal operation of the system.

[0035] The heat exchanger in the application is also connected with an electric steam boiler through a pipeline. The electric steam boiler is also connected with a high-pressure steam output pipeline and a photovoltaic power generation subsystem and a generator. When sunlight is not sufficient enough and water temperature is not high enough (it should be noted that this case considers that the electrode type molten salt boiler does not operate although sunlight is not sufficient enough), because the steam generator has limited power and cannot produce steam with required parameters, at this time, the electric steam boiler with higher power is used to produce high-parameter steam, and the steam produced by the steam generator is gathered and output through the high-pressure steam output pipeline. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0037] Figure 1 is a structural schematic diagram of the solar energy cascade utilization electric-thermal-steam combined supply system according to the application;

[0038] Figure 2 is a flow chart of the solar energy cascade utilization electric-thermal-steam combined supply method according to the application;

[0039] Figure: 1, softening water tank, 2, low temperature water supply pump, 3, low temperature heat pump, 4-1, first valve, 4-2, third valve, 4-3, second valve, 5, solar collector, 6, low temperature heat storage water tank, 7, low temperature water supply pump, 8, medium temperature heat storage water tank, 9, medium temperature water supply pump, 10, medium temperature water supply pump, 11, thermal deaerator, 111, thermal deaerator first inlet, 112, thermal deaerator outlet, 113, thermal deaerator second inlet, 12, heat exchanger, 121, heat exchanger heat source end inlet, 122, heat exchanger heat source end outlet, 123, heat exchanger heat exchange end outlet, 124, heat exchanger heat exchange end inlet, 13, light condensation collector, 14, electrode type molten salt boiler, 15, molten salt storage tank, 16, low temperature molten salt pump, 17, high temperature molten salt pump, 18, high temperature heat storage water tank, 19, high temperature water supply pump, 20, steam generator, 21, electric steam boiler, 22, back pressure steam turbine, 221, back pressure steam turbine inlet, 222, body air extraction port, 223, steam turbine outlet, 23, generator, 24, photovoltaic power generation module, 25, energy storage module, 26, power transmission module, a, softening water pipeline, b, low temperature return water pipeline, c, low temperature hot water output pipeline, d, medium temperature return water pipeline, e, medium temperature hot water output pipeline, f, high temperature return water pipeline, g, high parameter steam output pipeline, h, medium parameter steam output pipeline, k, low parameter steam output pipeline, L, high temperature hot water output pipeline. DETAILED DESCRIPTION

[0040] The advantages and effects of the present application can be easily understood by those skilled in the art from the description of the specific embodiments. The present application can also be implemented or applied by different specific embodiments, and the details in the description can be modified or changed based on different views and applications without departing from the spirit of the present application. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0041] Embodiment one:

[0042] Reference Figure 1 The embodiment provides a solar cascade utilization electric heat steam combined supply system, which comprises a first hot water supply subsystem, a heat exchange subsystem, a second hot water supply subsystem, a steam supply and generation subsystem and a photovoltaic power generation subsystem. The photovoltaic power generation subsystem is connected with the first hot water supply subsystem, the heat exchange subsystem, the second hot water supply subsystem and the steam supply and generation subsystem to provide electric energy, including providing electric energy for each pump body, and including providing electric energy for the low temperature heat pump 3, the electrode type molten salt boiler 14 and the electric steam boiler 21.

[0043] The first hot water supply subsystem comprises a water source supply module, a solar collector 5, a low-temperature hot water storage module, and a medium-temperature hot water storage module.

[0044] In the embodiment, the water source supply module comprises a softened water pipeline a, a softened water tank 1, and a low-temperature water supply pump 2. The low-temperature hot water storage module comprises a low-temperature heat storage water tank 6, a low-temperature hot water output pipeline c, and a low-temperature water supply pump 7 arranged on the low-temperature hot water output pipeline c. The medium-temperature hot water storage module comprises a medium-temperature heat storage water tank 8, a medium-temperature hot water output pipeline e, and a medium-temperature water supply pump 9 arranged on the medium-temperature hot water output pipeline e.

[0045] The solar collector 5 comprises a pipeline-connected solar primary heating submodule and a solar secondary heating submodule. The softened water tank 1 in the water source supply module is pipeline-connected with the solar primary heating submodule, and a low-temperature water supply pump 2 and a low-temperature return water pipeline b are arranged at the pipeline connection. The solar primary heating submodule is further pipeline-connected with the low-temperature heat storage water tank 6 in the low-temperature hot water storage module. The solar secondary heating submodule is further pipeline-connected with the medium-temperature heat storage water tank 8 in the medium-temperature hot water storage module.

[0046] The heat exchange subsystem comprises a concentrated collector 13, a molten salt storage tank 15, and a heat exchanger 12. The concentrated collector 5 is pipeline-connected with the molten salt storage tank 15. The concentrated collector 13 is further pipeline-connected with the heat source end of the heat exchanger 12. The heat exchange end inlet 124 of the heat exchanger is pipeline-connected with the solar secondary heating submodule. The heat exchange end outlet 123 of the heat exchanger is pipeline-connected with the high-temperature hot water storage module in the second hot water supply subsystem. The heat exchange end outlet 123 of the heat exchanger is further pipeline-connected with the steam supply and power generation subsystem.

[0047] The steam supply and power generation subsystem comprises a pipeline-connected steam generator 20 and a back pressure turbine 22, and further comprises a generator 23 connected with the back pressure turbine 22. The pipeline connection between the steam generator 20 and the back pressure turbine 22 is provided with a high-parameter steam output pipeline g. The back pressure turbine 22 is provided with a body air extraction port 222 and a turbine outlet 223. The body air extraction port 222 is connected with a medium-parameter steam output pipeline h. The turbine outlet 223 is connected with a low-parameter steam output pipeline k. The low-parameter steam has low temperature and pressure, and the high-parameter steam has high temperature and pressure.

[0048] The present application can utilize solar energy in stages, can provide hot water with high, medium, and low temperatures by using solar energy gradient, can provide steam with high, medium, and low parameters by using solar energy gradient, and can generate power by using the generated steam, so that solar energy is fully utilized.

[0049] The water is preliminarily heated by a solar primary heating sub-module in the solar collector 5, and then low-temperature hot water is obtained, and the low-temperature hot water is further heated by a solar secondary heating sub-module in the solar collector 5, so that medium-temperature hot water is obtained. Since the solar collector 5 has a temperature limit for heating water, a heat exchange subsystem is arranged in the application, the molten salt is heated by the light condensing collector 13, and the medium-temperature hot water is heat-transferred by the heated molten salt, so that the water temperature is further improved, and the operation cost of the light condensing collector 13 is higher than that of the solar collector 5, so that the heating of the low-temperature hot water and the medium-temperature hot water is performed by the solar collector 5, and the light condensing collector 13 only performs the heating of the high-temperature hot water, so that the operation cost of the system is reduced.

[0050] The application can produce high, medium and low parameter steam through the steam generator 20 and the back pressure turbine 22, and the medium and low parameter steam can be output through the body air outlet 222 and the turbine outlet 223 of the back pressure turbine 22, and the back pressure turbine 22 can directly drive the generator 23 to generate electricity while producing the medium and low parameter steam, so that the full and cascade utilization of energy is realized.

[0051] The photovoltaic power generation system comprises the photovoltaic power generation module 24, the energy storage module 25 and the power transmission module 26 connected in sequence, the power transmission module 26 is connected with the external power consumption module, and the power transmission module 26 is also connected with the external power taking module. That is, the photovoltaic power generation system can store the photovoltaic power generation energy in the energy storage module 25 for standby, and can also output to the external power consumption module for utilization, and when the energy in the combined supply system is insufficient, the external power taking module can be used to take power.

[0052] It should be further explained that the output end of the generator 23 is connected with the photovoltaic power generation system, and the generated electric energy can also be supplied to each subsystem in the combined supply system, and can also be transmitted to the energy storage module 25 for storage.

[0053] More specifically:

[0054] The output pipe and the input pipe are branched from the connecting pipe between the softened water tank 1 and the solar primary heating sub-module in the water source supply module, the first valve 4-1 is arranged on the output pipe, the second valve 4-2 is arranged on the input pipe, the third valve 4-2 is arranged between the output pipe and the input pipe, the low-temperature heat pump 3 is connected with the output pipe and the input pipe, and the low-temperature heat pump 3 is also connected with the photovoltaic power generation system and the generator 23.

[0055] That is, when the sunlight is not enough, by controlling the first valve 4-1, the second valve 4-3 is opened, the third valve 4-2 is controlled to be closed, so that the low-temperature heat pump 3 is used as a backup heat source to heat the water first, since the low-temperature heat pump 3 is connected with the photovoltaic power generation system, therefore, at any time, the work can be carried out through the electricity stored by the energy storage module 25, or through the valley electricity obtained from the external power acquisition module, to ensure the normal operation of the system. When the sunlight is sufficient, the first valve 4-1 and the second valve 4-3 are closed, and the third valve 4-2 is opened.

[0056] The solar secondary heating sub-module is connected with the first inlet 111 pipeline of the thermal deaerator, the outlet 112 of the thermal deaerator is connected with the heat exchange end inlet 124 pipeline of the heat exchanger, and the second inlet 113 of the thermal deaerator is connected with the low-parameter steam output pipeline k.

[0057] That is, the thermal deaerator 11 is arranged in the application, so that the oxygen in the hot water is removed, and the foundation is laid for subsequent steam production and power generation. And the heat source of the thermal deaerator 11 is the low-parameter steam output by the back pressure turbine 22, so that the energy can be more fully utilized.

[0058] The heat exchange subsystem further comprises an electrode type molten salt boiler 14, the electrode type molten salt boiler 14 is connected with the molten salt storage tank 15 through a pipeline, and the electrode type molten salt boiler 14 is connected with the photovoltaic power generation system and the generator 23.

[0059] That is, the heat exchange subsystem in the application further comprises an electrode type molten salt boiler 14, the electrode type molten salt boiler 14 is connected with the molten salt storage tank 15 through a pipeline, and the electrode type molten salt boiler 14 is connected with the photovoltaic power generation system and the generator 23, so that the electrode type molten salt boiler 14 can also be used as a backup heat source to heat the molten salt when the sunlight is not enough, and the normal operation of the system is ensured.

[0060] The heat exchange end outlet 123 of the heat exchanger is further connected with the electric steam boiler 21 through a pipeline, the electric steam boiler 21 is further connected with the high-parameter steam output pipeline g through a pipeline, and the electric steam boiler 21 is further connected with the photovoltaic power generation system and the generator 23.

[0061] That is, the heat exchanger in the present application is also connected with the electric steam boiler 21 at the heat exchange end outlet 123, the electric steam boiler 21 is also connected with the high-pressure steam output pipeline g, and the electric steam boiler 21 is also connected with the photovoltaic power generation system and the generator 23. When the sunlight is not sufficient and the water temperature is not high (it should be noted that the electrode type molten salt boiler 14 is not considered to be running in this case), due to the limited power of the steam generator 20, the steam with the required parameters cannot be generated, so the steam with high parameters is produced by the electric steam boiler 21 with higher power, and the steam produced by the steam generator 20 is converged and output through the high-pressure steam output pipeline g.

[0062] Referring to Figure 1 , the low-temperature return water pipeline b, the medium-temperature return water pipeline d, and the high-temperature return water pipeline f all play the role of returning water.

[0063] Embodiment two:

[0064] Referring to Figure 2 , the present embodiment provides a solar energy cascade utilization electric-thermal steam combined supply method, based on the solar energy cascade utilization electric-thermal steam combined supply system described in embodiment one, comprising the steps of:

[0065] S1, the water source supply module supplies water source to the solar primary heating submodule in the solar collector for preliminary heating to obtain low-temperature hot water;

[0066] S2, part of the low-temperature hot water is transported to the low-temperature hot water storage module for storage, and the rest of the low-temperature hot water is transported to the solar secondary heating submodule for further heating to obtain medium-temperature hot water;

[0067] S3, part of the medium-temperature hot water is transported to the medium-temperature hot water storage module for storage, and the rest of the medium-temperature hot water is transported to the heat exchanger in the heat exchange subsystem and exchanges heat with the molten salt heated by the concentrating collector to obtain high-temperature hot water;

[0068] S4, part of the high-temperature hot water is transported to the high-temperature hot water storage module for storage, and the rest of the high-temperature hot water is transported to the steam generator for evaporation to obtain high-parameter steam;

[0069] S5, part of the high-parameter steam is output through the high-parameter steam output pipeline, and the rest of the high-parameter steam is transported to the back pressure steam turbine, the body suction port of the back pressure steam turbine outputs medium-parameter steam through the medium-parameter steam output pipeline, the steam turbine outlet of the back pressure steam turbine outputs low-parameter steam through the low-parameter steam output pipeline, and the back pressure steam turbine outputs steam while driving the generator to generate electricity.

[0070] In step S3, the remaining medium-temperature hot water is subjected to thermal deaeration in a thermal deaerator before being delivered to the heat exchanger in the heat exchange subsystem, and the thermal deaerator is supplied with heat from the low-parameter steam output from the turbine outlet of the back-pressure steam turbine through a low-parameter steam output pipeline.

[0071] It should be noted that the solar energy cascade utilization electric-thermal combined heat and power supply method provided in the embodiment is similar to that in the first embodiment, and thus will not be described in detail herein.

[0072] The above-described embodiments are merely preferred embodiments of the present application, and are not intended to limit the scope of the present application. Various modifications and improvements to the technical solutions of the present application made by those of ordinary skill in the art without departing from the design spirit of the present application shall fall within the protection scope of the present application.

Claims

1. A solar cascade utilization of electricity, heat and steam cogeneration system, characterized in that, The system comprises a first hot water supply subsystem, a heat exchange subsystem, a second hot water supply subsystem, a steam supply subsystem and a photovoltaic power generation subsystem, wherein the photovoltaic power generation subsystem is connected with the first hot water supply subsystem, the heat exchange subsystem, the second hot water supply subsystem and the steam supply subsystem respectively. The first hot water supply subsystem comprises a water supply module, a solar energy collector and a low-temperature hot water storage module. The solar energy collector comprises a primary solar energy heating submodule and a secondary solar energy heating submodule connected by pipelines, the water supply module is connected with the primary solar energy heating submodule by pipelines, the primary solar energy heating submodule is further connected with the low-temperature hot water storage module by pipelines, and the secondary solar energy heating submodule is further connected with the medium-temperature hot water storage module by pipelines. The heat exchange subsystem comprises a concentrated solar energy collector, a molten salt storage tank and a heat exchanger, the concentrated solar energy collector is connected with the molten salt storage tank by pipelines, the concentrated solar energy collector is further connected with a heat source end of the heat exchanger by pipelines, an inlet of a heat exchange end of the heat exchanger is connected with the secondary solar energy heating submodule by pipelines, an outlet of the heat exchange end of the heat exchanger is connected with a high-temperature hot water storage module in the second hot water supply subsystem by pipelines, and the outlet of the heat exchange end of the heat exchanger is further connected with the steam supply subsystem by pipelines. The steam supply subsystem comprises a steam generator and a back pressure turbine connected by pipelines, and further comprises a generator connected with the back pressure turbine, wherein a high-parameter steam output pipeline is arranged at a pipeline connection position between the steam generator and the back pressure turbine, the back pressure turbine is provided with a body air outlet and a turbine outlet, the body air outlet is connected with a medium-parameter steam output pipeline, and the turbine outlet is connected with a low-parameter steam output pipeline. An output pipeline and an input pipeline are branched from a connection pipeline between the water supply module and the primary solar energy heating submodule, a first valve is arranged on the output pipeline, a second valve is arranged on the input pipeline, and a third valve is arranged between the output pipeline and the input pipeline at a position of the connection pipeline between the water supply module and the primary solar energy heating submodule, a low-temperature heat pump is connected with the output pipeline and the input pipeline respectively, and the low-temperature heat pump is further connected with the photovoltaic power generation subsystem and the generator. The heat exchange subsystem further comprises an electrode type molten salt boiler, the electrode type molten salt boiler is connected with the molten salt storage tank by pipelines, and the electrode type molten salt boiler is connected with the photovoltaic power generation subsystem and the generator.

2. The solar cascade utilization electric-thermal-vapor combined power system according to claim 1, characterized in that, The photovoltaic power generation subsystem comprises a photovoltaic power generation module, an energy storage module and a power transmission module connected in sequence, and the power transmission module is connected with an external power consumption module. 3.The solar energy cascade utilization electric-thermal-vapor combined system according to claim 2, characterized in that, The power transmission module is further connected with an external power acquisition module.

4. The solar cascade utilization electric-thermal-vapor combined power system according to claim 3, characterized in that, The secondary solar energy heating submodule is connected with a first inlet pipeline of a thermal deaerator, an outlet of the thermal deaerator is connected with an inlet pipeline of a heat exchange end of the heat exchanger, and a second inlet of the thermal deaerator is connected with a low-parameter steam output pipeline.

5. The solar cascade utilization of electricity, heat and steam cogeneration system according to claim 3, characterized in that, The outlet of the heat exchange end of the heat exchanger is further connected with an electric steam boiler by pipelines, the electric steam boiler is further connected with a high-parameter steam output pipeline by pipelines, and the electric steam boiler is further connected with the photovoltaic power generation subsystem and the generator.

6. The solar cascade utilization of electricity, heat and steam cogeneration system according to claim 1, characterized in that, The low-temperature hot water storage module comprises a low-temperature hot water storage tank and a low-temperature hot water output pipeline connected in sequence, a low-temperature water supply pump is arranged on the low-temperature hot water output pipeline, and the low-temperature water supply pump is connected with the photovoltaic power generation subsystem and the generator. The medium-temperature hot water storage module comprises a medium-temperature hot water storage tank and a medium-temperature hot water output pipeline connected with each other, and a medium-temperature water supply pump is arranged on the medium-temperature hot water output pipeline, and the medium-temperature water supply pump is connected with the photovoltaic power generation sub-system and the generator; The high-temperature hot water storage module comprises a high-temperature hot water storage tank and a high-temperature hot water output pipeline connected with each other, and a high-temperature water supply pump is arranged on the high-temperature hot water output pipeline, and the high-temperature water supply pump is connected with the photovoltaic power generation sub-system and the generator.

7. A method for solar cascade utilization of electricity, heat and steam, based on a solar cascade utilization system of electricity, heat and steam according to any one of claims 1 to 6, characterized in that The method comprises the following steps: S1, the water source supply module supplies water source to the solar primary heating sub-module in the solar collector for preliminary heating to obtain low-temperature hot water; S2, part of the low-temperature hot water is transported to the low-temperature hot water storage module for storage, and the rest of the low-temperature hot water is transported to the solar secondary heating sub-module for further heating to obtain medium-temperature hot water; S3, part of the medium-temperature hot water is transported to the medium-temperature hot water storage module for storage, and the rest of the medium-temperature hot water is transported to the heat exchanger in the heat exchange sub-system and exchanges heat with the molten salt heated by the concentrated solar collector to obtain high-temperature hot water; S4, part of the high-temperature hot water is transported to the high-temperature hot water storage module for storage, and the rest of the high-temperature hot water is transported to the steam generator for evaporation to obtain high-parameter steam; S5, part of the high-parameter steam is output through the high-parameter steam output pipeline, and the rest of the high-parameter steam is transported to the back pressure turbine, the body suction port of the back pressure turbine outputs medium-parameter steam through the medium-parameter steam output pipeline, the turbine outlet of the back pressure turbine outputs low-parameter steam through the low-parameter steam output pipeline, and the back pressure turbine outputs steam while driving the generator to generate electricity. 8.The method of claim 7, wherein, In step S3, before the rest of the medium-temperature hot water is transported to the heat exchanger in the heat exchange sub-system, it also passes through the thermal deaerator for thermal deaeration, and the heat source of the thermal deaerator is the low-parameter steam output by the turbine outlet of the back pressure turbine through the low-parameter steam output pipeline.

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