Photovoltaic-photothermal coupling heat pump and partition phase change heat storage system and operation method

Abstract

A photovoltaic-thermal coupled heat pump and zoned phase change thermal energy storage system and its operation method are disclosed, belonging to the field of solar energy comprehensive utilization and thermal energy storage technology. The system includes a photovoltaic power generation unit, a solar thermal collector unit, a cascade heat pump unit, a multi-temperature zone phase change thermal energy storage unit, and a control unit. The photovoltaic unit outputs direct current to directly drive the cascade heat pump; the solar thermal unit outputs heat energy to connect to the low-temperature thermal energy storage module in the multi-temperature zone thermal energy storage unit; the high-temperature stage condenser side of the cascade heat pump is connected to the medium-temperature and high-temperature thermal energy storage modules through a multi-branch valve group; each thermal energy storage module has an independent heat exchange circuit and is connected to the user side through a valve group. The system operation methods include a photovoltaic direct-drive cascade thermal energy storage mode, a solar thermal independent maintenance mode, and a thermal energy storage module heat release mode. This invention realizes the synergistic utilization of solar photovoltaic and solar thermal energy, and matches different heat load demands through multi-temperature zone thermal energy storage.

Description

Technical Field

[0001] This invention belongs to the fields of distributed clean heating, efficient utilization of renewable energy and energy storage technology. Specifically, it relates to an integrated thermal energy management system that integrates photovoltaic power generation, solar thermal collection, compression heat pump and temperature zone phase change thermal storage. It is suitable for multi-temperature heating scenarios such as building heating, industrial process heating, hot water supply and steam preparation. Background Technology

[0002] Solar energy, as a clean and renewable energy source, is increasingly widely used in the heating sector. Currently, solar heating mainly relies on two technical paths: photovoltaic power generation driving electric heating equipment or direct heat generation through solar thermal collectors. Photovoltaic power generation suffers from intermittency and strong fluctuations. When directly driving a heat pump, the traditional method requires multiple stages of power conversion, including DC-AC-frequency conversion, resulting in significant losses, slow dynamic response, and a frequent mismatch between photovoltaic output and peak heat load. Solar thermal collectors can provide continuous heat energy, but the quality is usually low (<90℃), making it difficult to meet the medium- and high-temperature requirements of industrial processes and steam preparation.

[0003] Thermal energy storage technology is key to addressing the spatial and temporal mismatch between energy supply and demand. Conventional thermal energy storage systems often employ storage materials with a single temperature range (such as water tank storage or single-phase change-point materials), making it difficult to adapt to the diverse and tiered heat load demands prevalent in building and industrial settings. While technologies such as cascade heat pumps can generate high-temperature heat, a systematic solution remains lacking for efficiently and stably coupling fluctuating solar energy with multi-temperature zone heat loads. Existing technologies typically treat photovoltaics, solar thermal, heat pumps, and thermal energy storage as simple, independent units, failing to achieve tiered energy utilization and synergistic optimization. This results in low overall system energy efficiency and limited adaptability to fluctuations in photovoltaic power. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a photovoltaic-thermal coupled heat pump and a zoned phase change thermal storage system and its operation method, in order to achieve cascaded utilization and synergistic optimization of energy and improve the overall energy efficiency of the system.

[0005] The technical solution adopted in this invention is: a photovoltaic-thermal coupled heat pump and zoned phase change thermal storage system, comprising:

[0006] A photovoltaic power generation module is used to convert solar energy into DC power, and its output is connected to the DC main line via a maximum power point tracking controller;

[0007] Solar thermal collector modules are used to collect solar energy and output low-temperature heat energy;

[0008] The compression heat pump module has its power input terminal connected to the DC main line and is directly driven by photovoltaic DC power; its condenser side is equipped with multiple heating branches.

[0009] The partitioned phase change thermal energy storage module includes at least three independent thermal energy storage units, namely a first thermal energy storage module, a second thermal energy storage module, and a third thermal energy storage module. Each thermal energy storage module is encapsulated with a phase change material with a different phase change temperature range and is equipped with an independent heat exchange circuit. The output end of the solar thermal collector module is connected to the heat exchange circuit of the low-temperature thermal energy storage unit. Multiple heating branches on the condenser side of the compression heat pump module are connected to the heat exchange circuits of the medium-temperature thermal energy storage unit and the high-temperature thermal energy storage unit respectively through a multi-branch valve group.

[0010] The user-side heat exchange unit is selectively connected to the heat exchange circuit of each heat storage unit through a user-side valve group; the user-side heat exchange unit includes low-temperature users, medium-temperature users and high-temperature users;

[0011] The control unit is used to monitor system parameters and control the operation of the compression heat pump module, the multi-branch valve group, and the user-side valve group.

[0012] Furthermore, the compression heat pump module has a two-stage compression or cascade compression structure.

[0013] Furthermore, the phase change temperature ranges of the phase change materials in the first, second, and third thermal storage modules are 60-80℃, 90-120℃, and 130-160℃, respectively.

[0014] Furthermore, each thermal storage unit has an independent heat exchange circuit equipped with an independent circulation pump.

[0015] Furthermore, the multi-branch valve assembly includes a three-way valve and an electronic expansion valve.

[0016] Furthermore, the required temperature for low-temperature users is greater than 60℃ and less than or equal to 95℃, the required temperature for high-temperature users is greater than 95℃ and less than or equal to 140℃, and the required temperature for high-temperature users is greater than 140℃ and less than or equal to 170℃.

[0017] A method of operating the system includes the following modes:

[0018] Photovoltaic direct-drive heat charging mode: When the photovoltaic output reaches the start-up threshold of the compression heat pump module, the compression heat pump module is started; the control unit controls the multi-branch valve group to direct the condensation heat generated by the heat pump to the medium-temperature heat storage unit and the high-temperature heat storage unit for heat charging;

[0019] The solar thermal collector module simultaneously heats the low-temperature thermal storage unit;

[0020] Photothermal maintenance mode: When the photovoltaic output is lower than the start-up threshold and the output temperature of the photothermal collector module is higher than the temperature in the first thermal storage module, the compression heat pump module is controlled to stop or operate at reduced load, and the temperature of the first thermal storage module is maintained by the photothermal collector module.

[0021] Thermal storage and release mode: When there is a heat demand on the user side, the control unit connects the heat exchange circuit of the thermal storage module in the corresponding temperature zone to the heat exchange unit on the user side through the user-side valve group according to the demand temperature, and releases the stored heat.

[0022] Furthermore, when using the heat storage and release mode, the control unit operates the user-side switching valve group according to the required temperature; when the required temperature is greater than 60℃ and less than or equal to 95℃, the first heat storage module is connected to the low-temperature user; when the required temperature is greater than 95℃ and less than or equal to 140℃, the second heat storage module is connected to the medium-temperature user; when the required temperature is greater than 140℃ and less than or equal to 170℃, the third heat storage module is connected to the high-temperature user, and heat is directly released from the heat storage module to the user.

[0023] The beneficial effects of this invention are as follows: This system achieves multi-faceted conversion and efficient utilization of solar energy through the coordinated layout of photovoltaic power generation modules and solar thermal collector modules. Photovoltaic DC power directly drives the compression heat pump module, eliminating the need for additional power conversion stages, significantly reducing energy loss and operating costs. Simultaneously, combined with a maximum power point tracking controller, it improves the utilization rate of photovoltaic output. The zoned phase change thermal storage module is equipped with three independent thermal storage units, using phase change materials with different phase change temperature ranges and independent heat exchange circuits. This allows for targeted storage of low-temperature heat energy generated by the solar thermal module and medium-to-high-temperature heat energy generated by the heat pump module, effectively solving the energy supply fluctuation problem caused by the intermittency and instability of solar energy, ensuring the continuity and stability of the system's energy supply. Through the coordinated control of multiple branch valve groups and user-side valve groups, the thermal storage units in the corresponding temperature zones can be precisely matched to release heat according to the different heat demands of users at low, medium, and high temperatures, avoiding heat waste and significantly improving the system's heat supply adaptability and energy utilization efficiency. Meanwhile, the dual-stage or cascade compression structure of the heat pump design can improve the heat pump's heating efficiency and high-temperature heating capacity, adapting to heating needs in different scenarios. It can be widely used in various scenarios requiring tiered heating, resulting in significant economic and environmental benefits. This invention achieves the synergistic utilization of solar photovoltaic and solar thermal energy, and matches different grades of heat load requirements through multi-temperature zone heat storage. Attached Figure Description

[0024] Figure 1 is a structural diagram of a photovoltaic-thermal coupled phase change thermal energy storage system with temperature zones.

[0025] In the diagram: 1. Photovoltaic array, 2. MPPT controller, 3. DC main line, 4. Cascade heat pump unit, 5. Solar thermal collector, 6. Multi-branch distribution valve group, 7. Multi-temperature zone phase change thermal storage unit, 7a. First thermal storage module, 7b. Second thermal storage module, 7c. Third thermal storage module, 8. User-side switching valve group, 9. User-side heat exchange unit, 9a. Low-temperature user, 9b. Medium-temperature user, 9c. High-temperature user, 10. Control unit. Detailed Implementation

[0026] The present invention will now be described in conjunction with the accompanying drawings and embodiments.

[0027] A photovoltaic-thermal coupled cascade heat pump and multi-temperature zone phase change thermal storage system includes a photovoltaic power generation unit, a solar thermal collector unit, a cascade heat pump unit, a multi-temperature zone phase change thermal storage unit, a user-side heat exchange unit, a valve system, and a control unit.

[0028] The photovoltaic power generation unit is connected to the DC main line via a maximum power point tracking controller. The DC main line is directly connected to the compressor of the cascade heat pump unit.

[0029] The output of the photothermal collector unit is connected to the first thermal storage module in the multi-temperature zone phase change thermal storage unit.

[0030] The cascade heat pump unit comprises a low-temperature stage cycle and a high-temperature stage cycle. The condenser-side outlet of its high-temperature stage cycle is connected to a multi-branch distribution valve assembly, which distributes heat to the second and third heat storage modules in the multi-temperature zone phase change heat storage unit.

[0031] The multi-temperature zone phase change thermal energy storage unit includes three independent thermal energy storage modules. The first, second, and third thermal energy storage modules are respectively encapsulated with phase change materials with different phase change temperature ranges, namely organic thermal energy storage materials, inorganic hydrated salt thermal energy storage materials, and molten salt composite phase change materials. Each thermal energy storage module has an independent heat exchange circuit.

[0032] The valve system includes a multi-branch distribution valve assembly and a user-side switching valve assembly. The user-side switching valve assembly is used to selectively connect the heat exchange circuits of each thermal storage module to the user-side heat exchange unit.

[0033] The control unit is used to monitor and control the operation of the entire system.

[0034] This invention also provides a method for operating the system, including the following three modes:

[0035] Photovoltaic direct-drive cascaded thermal storage mode: When photovoltaic output is sufficient, the cascaded heat pump is activated. The solar thermal unit heats the first thermal storage module. The medium-to-high temperature heat generated by the heat pump is used to cascade heat the second and third thermal storage modules through a multi-branch distribution valve group.

[0036] Solar thermal stand-alone maintenance mode: When photovoltaic output is insufficient, the heat pump stops or operates at reduced load. Only solar thermal energy is used to maintain the temperature of the first thermal storage module.

[0037] Thermal storage module heat release mode: When a user needs heat, the thermal storage module in the corresponding temperature zone is directly supplied with heat by switching valves on the user side according to the required temperature.

[0038] The present invention will be specifically described below through embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention, but are not limited thereto, unless otherwise stated.

[0039] The specific embodiments of the present invention are described in detail below with reference to the technical solutions:

[0040] Example 1

[0041] Figure 1 This is a structural diagram of a photovoltaic-thermal coupled multi-temperature zone phase change thermal energy management system. In the diagram, the system includes a photovoltaic array 1, a cascaded heat pump unit 4, a solar collector 5, a multi-temperature zone phase change thermal energy storage unit 7, and a user-side heat exchange unit 9.

[0042] The multi-temperature zone phase change thermal energy storage unit 7 comprises three independent thermal energy storage modules. The multi-temperature zone phase change thermal energy storage unit 7 includes a first thermal energy storage module 7a for storing low-temperature heat, a second thermal energy storage module 7b for storing medium-temperature heat, and a third thermal energy storage module 7c for storing high-temperature heat. The first thermal energy storage module 7a encapsulates a phase change material with a phase change temperature of approximately 70°C. The second thermal energy storage module 7b encapsulates a phase change material with a phase change temperature of approximately 105°C. The third thermal energy storage module 7c encapsulates a phase change material with a phase change temperature of approximately 145°C. Each thermal energy storage module is equipped with a circulation pump at the heat exchange loop outlet.

[0043] User-side heat exchange unit 9 includes low-temperature users 9a who require domestic hot water at 60-95℃, medium-temperature users 9b who require process heating at 100-140℃, and high-temperature users 9c who require steam at 140-170℃.

[0044] The DC power output from photovoltaic array 1 is optimized by MPPT controller 2 and then fed into DC main line 3. DC main line 3 directly powers the low-temperature stage compressor and high-temperature stage compressor of cascade heat pump unit 4. The high-temperature outlet of cascade heat pump unit 4 is connected to multi-branch distribution valve group 6. The two outlet branches of valve group 6 are respectively connected to the heat exchange circuit inlet of the second thermal storage module 7b and the third thermal storage module 7c, storing the thermal energy of cascade heat pump unit 4 respectively. The bottoms of the second thermal storage module 7b and the third thermal storage module 7c are respectively connected to the user-side switching valve group 8 through pipelines, and the user-side heat exchange unit 9 is supplied with heat through the switching of the valve group.

[0045] The output pipeline of the solar thermal collector 5 is connected to the inlet of the heat exchange circuit of the first heat storage module 7a. The outlet of the first heat storage module 7a is connected to the user-side switching valve group 8 through a pipeline. The user-side heat exchange unit 9 is supplied with heat through the switching of the valve group.

[0046] User-side heat exchange unit 9 includes user terminals at different temperatures: low-temperature user 9a (e.g., hot water system), medium-temperature user 9b (e.g., process heating), and high-temperature user 9c (e.g., steam generation). The heat exchange circuit of each heat storage module can be selectively connected to these user terminals through user-side switching valve group 8.

[0047] The control unit 10 is electrically connected to the multi-branch distribution valve group 6, the cascade heat pump unit 4, and the user-side switching valve group 8. The control unit 10 receives sensor signals from various parts of the system and outputs control commands.

[0048] The system operates as follows:

[0049] When there is sufficient sunlight, i.e., when the photovoltaic output reaches the start-up threshold of the compression heat pump module, the system enters the photovoltaic direct-drive cascade heat storage mode. The solar thermal collector 5 heats the first heat storage module 7a. The control unit 10 starts the cascade heat pump 4, and the medium-temperature and high-temperature heat generated by the heat pump is distributed through the multi-branch distribution valve group 6 to charge the second heat storage module 7b and the third heat storage module 7c.

[0050] When the photovoltaic output decreases (e.g., on a cloudy day), i.e., when the photovoltaic output falls below the start-up threshold and the output temperature of the solar thermal collector module is higher than the temperature in the first thermal storage module, the system enters a solar thermal standby mode. The control unit 10 shuts down the cascade heat pump 4. The heat output from the solar thermal collector 5 is used to maintain the temperature of the first thermal storage module 7a.

[0051] When a user has a heat demand, the system enters the heat release mode of the thermal storage module. The control unit 10 operates the user-side switching valve group 8 according to the required temperature. For example, if 85℃ hot water is needed, the first thermal storage module 7a is connected to the low-temperature user 9a; if 120℃ process heat is needed, the second thermal storage module 7b is connected to the medium-temperature user 9b; and if 150℃ steam is needed, the third thermal storage module 7c is connected to the high-temperature user 9c. Heat is released directly from the thermal storage module to the user.

[0052] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A photovoltaic-thermal coupled heat pump and zoned phase change thermal storage system, characterized in that... include: A photovoltaic power generation module is used to convert solar energy into DC power, and its output is connected to the DC main line via a maximum power point tracking controller; Solar thermal collector modules are used to collect solar energy and output low-temperature heat energy; The compression heat pump module has its power input terminal connected to the DC main line and is directly driven by photovoltaic DC power; its condenser side is equipped with multiple heating branches. The partitioned phase change thermal energy storage module includes at least three independent thermal energy storage units, namely a first thermal energy storage module, a second thermal energy storage module, and a third thermal energy storage module. Each thermal energy storage module is encapsulated with a phase change material with a different phase change temperature range and is equipped with an independent heat exchange circuit. The output end of the solar thermal collector module is connected to the heat exchange circuit of the low-temperature thermal energy storage unit. Multiple heating branches on the condenser side of the compression heat pump module are connected to the heat exchange circuits of the medium-temperature thermal energy storage unit and the high-temperature thermal energy storage unit respectively through a multi-branch valve group. The user-side heat exchange unit is selectively connected to the heat exchange circuit of each heat storage unit through a user-side valve group; the user-side heat exchange unit includes low-temperature users, medium-temperature users and high-temperature users; The control unit is used to monitor system parameters and control the operation of the compression heat pump module, the multi-branch valve group, and the user-side valve group.

2. The system according to claim 1, characterized in that, The compression heat pump module has a two-stage compression or cascade compression structure.

3. The system according to claim 2, characterized in that, The phase change temperature ranges of the phase change materials in the first, second, and third thermal storage modules are 60-80℃, 90-120℃, and 130-160℃, respectively.

4. The system according to claim 3, characterized in that, Each thermal storage unit has an independent heat exchange circuit equipped with an independent circulation pump.

5. The system according to claim 4, characterized in that, The multi-branch valve group includes a three-way valve and an electronic expansion valve.

6. The system according to claim 5, characterized in that, Low-temperature users require a temperature greater than 60℃ and less than or equal to 95℃, low-temperature users require a temperature greater than 95℃ and less than or equal to 140℃, and high-temperature users require a temperature greater than 140℃ and less than or equal to 170℃.

7. A method for operating the system as described in claim 6, characterized in that, Includes the following modes: Photovoltaic direct-drive heat charging mode: When the photovoltaic output reaches the start-up threshold of the compression heat pump module, the compression heat pump module is started; the control unit controls the multi-branch valve group to direct the condensation heat generated by the heat pump to the medium-temperature heat storage unit and the high-temperature heat storage unit for heat charging; The solar thermal collector module simultaneously heats the low-temperature thermal storage unit; Photothermal maintenance mode: When the photovoltaic output is lower than the start-up threshold and the output temperature of the photothermal collector module is higher than the temperature in the first thermal storage module, the compression heat pump module is controlled to stop or operate at reduced load, and the temperature of the first thermal storage module is maintained by the photothermal collector module. Thermal storage and release mode: When there is a heat demand on the user side, the control unit connects the heat exchange circuit of the thermal storage module in the corresponding temperature zone to the heat exchange unit on the user side through the user-side valve group according to the demand temperature, and releases the stored heat.

8. The method of operating the system according to claim 7, characterized in that: When using the heat storage and release mode, the control unit operates the user-side switching valve group according to the required temperature; when the required temperature is greater than 60℃ and less than or equal to 95℃, the first heat storage module is connected to the low-temperature user; when the required temperature is greater than 95℃ and less than or equal to 140℃, the second heat storage module is connected to the medium-temperature user; when the required temperature is greater than 140℃ and less than or equal to 170℃, the third heat storage module is connected to the high-temperature user, and heat is directly released from the heat storage module to the user.

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