Photovoltaic photo-thermal two-stage heat pump system

Abstract

The utility model discloses a photovoltaic photo-thermal two-stage heat pump system which comprises a photovoltaic photo-thermal system, a first-stage heat pump system, a buffer water tank system and a second-stage heat pump system, an outlet of a heat collector refrigerant pipe of the photovoltaic photo-thermal system is divided into two paths, one path is connected with an inlet in one side of a first-stage evaporator through a first pipeline, and the other path is connected with an outlet in the other side of a second-stage evaporator through a second pipeline. An outlet in one side of the first-stage evaporator is connected to a refrigerant inlet of the heat collector through a fourth valve; the other path is connected to a first path inlet of the second-stage evaporator through a first pipeline, and a first path outlet of the second-stage evaporator is connected with a refrigerant inlet of the heat collector; the first-stage heat pump system comprises a first-stage heat pump heating circulating system and a first-stage heat pump refrigerating circulating system. According to the utility model, the heat pump can be utilized to take away the power generation waste heat of the photovoltaic module in time, and the phenomenon of power generation efficiency reduction caused by overhigh temperature of the photovoltaic module is relieved; the evaporation temperature of the heat pump can be increased through solar energy, the thermal performance of the system is improved, and therefore advantage complementation and gradient utilization of clean energy are achieved.

Description

Technical Field

[0001] This utility model relates to the field of heat pumps, and in particular to a photovoltaic-thermal dual-stage heat pump system. Background Technology

[0002] Heat pump technology, as a highly efficient and environmentally friendly energy utilization method, has experienced rapid development in China in recent years. With the nation's emphasis on energy conservation, emission reduction, and renewable energy utilization, coupled with the continuous development of China's economy and society and the constant improvement of people's living standards, the heat pump industry is showing a vigorous development trend driven by both policy support and market demand. The market demand for heat pump technology will continue to expand. Especially in northern regions, the market demand for heat pump equipment will be even stronger with the arrival of the heating season. At the same time, with the increasing demand for energy conservation and emission reduction in the industrial sector, the application of heat pumps in industrial refrigeration, drying, and other fields will be further expanded.

[0003] Existing heat pumps include photovoltaic heat pumps and two-stage coupled cascade heat pump systems.

[0004] The heat pump system operates as follows:

[0005] During winter heating, the high-pressure vapor discharged from the compressor enters the condenser. The latent heat released when the refrigerant vapor condenses heats the indoor air, achieving the purpose of indoor heating. The condensed liquid refrigerant flows through the expansion valve into the evaporator, where it absorbs heat from the outside and evaporates. The evaporated vapor is then drawn into the compressor after passing through the reversing valve, completing the heating cycle.

[0006] During summer cooling, the system operates under refrigeration conditions. In the indoor heat exchanger, the refrigerant absorbs heat and evaporates, lowering the indoor temperature. The evaporated refrigerant then enters the compressor through a four-way reversing valve, forming high-temperature, high-pressure vapor. It then releases heat and cools down in the outdoor heat exchanger, i.e., condenses. After being depressurized by a throttling device, it returns to the indoor side to absorb heat, forming a cycle.

[0007] Photovoltaic thermal integrated (PVT) heat pumps are an effective way to actively utilize solar radiation energy. As an emerging cogeneration system, they can not only remove the waste heat generated by photovoltaic modules in a timely manner, thus reducing the operating temperature of the photovoltaic modules, but also effectively recover waste heat while improving power generation efficiency, thereby achieving high-efficiency solar cogeneration.

[0008] The two-stage cascade heat pump system utilizes two sets of refrigerants. The first set of refrigerants achieves heating from ultra-low temperature to medium-low temperature, while the second set of refrigerants achieves heating from medium-low temperature to high temperature, enabling high-temperature heating in ultra-low temperature environments.

[0009] Photovoltaic-thermal integrated heat pumps are single units, which can only achieve relatively low outlet water temperatures, limiting their applicable application areas. Two-stage cascade heat pump systems, on the other hand, can only operate in two stages and cannot adjust to rising ambient temperatures, resulting in energy waste. Furthermore, simple cascaded two-stage heat pumps cannot achieve cooling functionality. Utility Model Content

[0010] The purpose of this utility model embodiment is to address the deficiencies of the prior art by providing a photovoltaic-thermal dual-stage heat pump system capable of both heating and cooling functions.

[0011] To achieve the above objectives, the technical solution adopted by this utility model is as follows:

[0012] A photovoltaic-thermal dual-stage heat pump system includes a photovoltaic-thermal system, a primary heat pump system, a buffer water tank system, and a secondary heat pump system;

[0013] The photovoltaic thermal system includes a photovoltaic panel. A refrigerant pipe for a collector is attached to the back of the photovoltaic panel. The outlet of the refrigerant pipe for the collector is divided into two paths. One path connects to one side inlet of the first-stage evaporator through a first pipe and a second pipe in sequence. The outlet of the first-stage evaporator is connected to the refrigerant inlet of the collector through a fourth valve and a second circulation pump in sequence. The other path connects to the first inlet of the second-stage evaporator through a first pipe, a third pipe, a fifth valve, and a fourth pipe in sequence. The first outlet of the second-stage evaporator is connected to the refrigerant inlet of the collector through a fifth pipe, a third valve, and a second circulation pump in sequence.

[0014] The primary heat pump system includes a primary heat pump heating cycle system and a primary heat pump cooling cycle system.

[0015] The primary heat pump heating cycle system includes a primary evaporator. The other outlet of the primary evaporator is connected to a primary compressor via a four-way reversing valve, a first filter, and a gas-liquid separator. The primary compressor is connected to one inlet of a primary condenser via a four-way reversing valve. The one outlet of the primary condenser is connected to one inlet of a primary economizer via a primary liquid receiver. The one outlet of the primary economizer is divided into two paths after passing through a dryer filter: a main path and a make-up gas path. The make-up gas path is connected to the other inlet of the primary economizer via an auxiliary electronic expansion valve. The other outlet of the primary economizer is connected to the make-up gas port of the primary compressor. The main path is connected to the other inlet of the primary evaporator via a dryer filter, a main electronic expansion valve, and a second filter.

[0016] The first-stage heat pump refrigeration cycle system includes a first-stage evaporator. The outlet of the first-stage evaporator is split into two paths after passing through a second filter. One path is connected to one side inlet of the first-stage condenser through a first-stage main electronic expansion valve, a dryer filter, an economizer, and a liquid receiver in sequence. The other path is connected to the liquid receiver through a capillary check valve and a capillary tube in sequence. One side outlet of the first-stage condenser is connected to the inlet of the first-stage compressor through a four-way reversing valve, a first filter, and a first-stage gas-liquid separator. The outlet of the first-stage compressor is connected to the other side inlet of the first-stage evaporator through a four-way reversing valve.

[0017] The buffer water tank system includes a buffer water tank. The outlet of the buffer water tank is connected to the other inlet of the first-stage condenser via a tenth pipe. The other outlet of the first-stage condenser is divided into two paths. One path is connected to the second inlet of the second-stage evaporator via a sixth pipe, a third circulation pump, and an eighth pipe. The second outlet of the second-stage evaporator is connected to the first inlet of the buffer water tank via a ninth pipe. The other path is connected to the terminal water supply line via a sixth pipe and a seventh pipe. The terminal return water line is connected to the second inlet of the buffer water tank via a first circulation pump, an eleventh pipe, a second valve, and a twelfth pipe.

[0018] The secondary heat pump system includes a secondary evaporator. The third outlet of the secondary evaporator is connected to the inlet of the secondary compressor via a third filter and a secondary gas-liquid separator. The outlet of the secondary compressor is connected to one side inlet of the secondary condenser. The one side outlet of the secondary condenser is connected to the third inlet of the secondary evaporator via a secondary liquid receiver, a fourth filter, and a secondary electronic expansion valve.

[0019] The terminal water supply pipeline is connected to the other outlet of the secondary condenser, and the other inlet of the secondary condenser is connected to the first circulation pump through the first valve.

[0020] The collector refrigerant pipe is equipped with heat dissipation fins, and the working fluid of the collector refrigerant pipe is antifreeze. The collector refrigerant pipe and the photovoltaic panel transfer heat through the antifreeze.

[0021] The primary evaporator is a dual-channel plate heat exchanger; the secondary evaporator is a three-channel plate heat exchanger.

[0022] The working fluid in one channel of the three-channel heat exchanger is antifreeze, the working fluid in another channel is water, and the working fluid in the third channel is fluorine.

[0023] The first valve, the second valve, the third valve, the fourth valve, and the fifth valve are all electric valves.

[0024] Both the seventh and eighth pipes are equipped with check valves.

[0025] The buffer tank is equipped with an electric heater.

[0026] The beneficial effects of the technical solution provided by this utility model embodiment are:

[0027] This invention combines photovoltaic thermal technology with two-stage compression technology, along with a buffer water tank system, to achieve heating and cooling effects simultaneously while generating electricity. When ambient temperatures vary, the photovoltaic thermal two-stage heat pump can achieve heating and cooling functions by adjusting the single / dual-stage operation mode or by operating in a single-stage or two-stage configuration. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of the photovoltaic-thermal dual-stage heat pump system provided in this embodiment of the utility model;

[0029] Figure 2 This is a diagram of a solar thermal primary heat pump heating cycle system provided in an embodiment of this utility model;

[0030] Figure 3 This is a diagram of a primary heat pump refrigeration system provided in an embodiment of this utility model;

[0031] Figure 4 This is a diagram of a two-stage solar thermal heat pump heating cycle system provided in this embodiment of the utility model;

[0032] Figure 5 This is a diagram of a two-stage heat pump circulation system provided in an embodiment of this utility model.

[0033] In the picture:

[0034] 1-1 Photovoltaic panel, 1-2 Refrigerant pipe for collector, 1-3 Heat dissipation fins, 2-1 First-stage evaporator, 2-2 Four-way reversing valve, 2-3 First filter, 2-4 Gas-liquid separator, 2-5 First-stage compressor, 2-6 First-stage condenser, 2-7 Liquid receiver, 2-8 Economizer, 2-9 Dryer filter, 2-10 Auxiliary electronic expansion valve, 2-11 Main electronic expansion valve, 2-12 Second filter, 2-13 Capillary check valve, 2-14 Capillary tube, 3-1 Second-stage evaporator, 3-2 Third filter, 3-3 Gas-liquid separator, 3-4 Second-stage compressor, 3-5 Second-stage condenser, 3-6 Liquid receiver, 3-7 Fourth filter, 3-8 Second-stage electronic expansion valve, 4-1 First valve, 4-2 Second valve, 4-3 Third valve, 4-4 Fourth valve, 4-5 Fifth valve, 5-1 First circulation pump, 5-2 Second circulation pump, 5-3 Third circulation pump.

[0035] 1-First pipe, 2-Second pipe, 3-Third pipe, 4-Fourth pipe, 5-Fifth pipe, 6-Sixth pipe, 7-Seventh pipe, 8-Eighth pipe, 9-Ninth pipe, 10-Tenth pipe, 11-Eleventh pipe, 12-Twelfth pipe, 13-End return water pipe, 14-End supply water pipe, 15-Buffer water tank, 16-Check valve.

[0036] Figure 1 , Figure 2 , Figure 4 , Figure 5 The arrows in the diagram indicate the direction of solar radiation. Figure 3 The arrows in the diagram indicate the direction of heat dissipation from the fins. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this utility model clearer, the embodiments of this utility model will be described in further detail below with reference to the accompanying drawings.

[0038] See Figure 1 A photovoltaic-thermal dual-stage heat pump system includes a photovoltaic-thermal system, a primary heat pump system, a buffer water tank system, and a secondary heat pump system.

[0039] The photovoltaic thermal system includes a photovoltaic panel 1-1, a collector refrigerant pipe 1-2, and heat dissipation fins 1-3; the outlet of the collector refrigerant pipe 1-2 is connected to one side inlet of the first-stage evaporator 2-1 through the first pipe 1 and the second pipe 2 in sequence, and the outlet of the first-stage evaporator 2-1 is connected to the inlet of the collector refrigerant pipe 1-2 through the fourth valve 4-4 and the second circulation pump 5-2 in sequence, forming a first circulation loop, namely, a photovoltaic thermal power supply first-stage heat pump circulation loop;

[0040] The outlet of the refrigerant pipe 1-2 of the solar collector is connected to the first inlet of the secondary evaporator 3-1 in sequence through the first pipe 1, the third pipe 3, the fifth valve 4-5 and the fourth pipe 4. The first outlet of the secondary evaporator 3-1 is connected to the inlet of the refrigerant pipe 1-2 of the solar collector in sequence through the fifth pipe 5, the third valve 4-3 and the second circulation pump 5-2, forming a second circulation loop, namely the solar thermal secondary heat pump circulation loop.

[0041] The first-stage heat pump heating cycle system includes a first-stage evaporator 2-1. The other outlet of the first-stage evaporator 2-1 is connected to a first-stage compressor 2-5 via a four-way reversing valve 2-2, a first filter 2-3, and a gas-liquid separator 2-4. The first-stage compressor 2-5 is connected to one inlet of a first-stage condenser 2-6 via a four-way reversing valve 2-2. The one outlet of the first-stage condenser 2-6 is connected to one inlet of a first-stage economizer 2-8 via a first-stage liquid receiver 2-7. The one outlet of the first-stage economizer 2-8 is split into two paths after passing through a dryer filter 2-9: one is the main path, and the other is the make-up gas path. The make-up gas path is connected to the other inlet of the first-stage economizer 2-8 via an auxiliary electronic expansion valve 2-10. The other outlet of the first-stage economizer 2-8 is connected to the make-up gas port of the first-stage compressor 2-5. The main path is connected to the other inlet of the first-stage evaporator 2-1 via a dryer filter 2-9, a main electronic expansion valve 2-11, and a second filter 2-12, forming a third circulation loop, i.e., the first-stage heat pump heating cycle.

[0042] The first-stage heat pump refrigeration cycle system includes a first-stage evaporator 2-1. The outlet of the first-stage evaporator 2-1 is split into two paths after passing through a second filter 2-12. One path is connected to one side inlet of the first-stage condenser 2-6 via a first-stage main electronic expansion valve 2-11, a dryer filter 2-9, an economizer 2-8, and a liquid receiver 2-7. The other path is connected to the liquid receiver 2-7 via a capillary check valve 2-13 and a capillary tube 2-14. One side outlet of the first-stage condenser 2-6 is connected to the inlet of the first-stage compressor 2-5 via a four-way reversing valve 2-2, a first filter 2-3, and a first-stage gas-liquid separator 2-4. The outlet of the first-stage compressor 2-5 is connected to the other side inlet of the first-stage evaporator 2-1 via a four-way reversing valve 2-2, forming a fourth circulation loop, i.e., the first-stage heat pump refrigeration cycle.

[0043] The buffer tank system includes a buffer tank 15. The outlet of the buffer tank 15 is connected to the other inlet of the primary condenser 2-6 via the tenth pipe 10. The other outlet of the primary condenser 2-6 is divided into two paths. One path is connected to the second inlet of the secondary evaporator 3-1 via the sixth pipe 6, the third circulation pump 5-3, and the eighth pipe 8. The second outlet of the secondary evaporator 3-1 is connected to the first inlet of the buffer tank 15 via the ninth pipe 9, forming the fifth circulation loop, i.e., the buffer tank supplies the secondary heat pump circulation loop. The other path is connected to the terminal water supply pipe 14 via the sixth pipe 6 and the seventh pipe 7. The terminal return water pipe 13 is connected to the second inlet of the buffer tank 15 via the first circulation pump 5-1, the eleventh pipe 11, the second valve 4-2, and the twelfth pipe 12, forming the sixth circulation loop, i.e., the primary heat pump direct heating loop.

[0044] The secondary heat pump system includes a secondary evaporator 3-1. The third outlet of the secondary evaporator 3-1 is connected to the inlet of the secondary compressor 3-4 via a third filter 3-2 and a secondary gas-liquid separator 3-3. The outlet of the secondary compressor 3-4 is connected to one side inlet of the secondary condenser 3-5. The one side outlet of the secondary condenser 3-5 is connected to the third inlet of the secondary evaporator 3-1 via a secondary liquid receiver 3-6, a fourth filter 3-7, and a secondary electronic expansion valve 3-8, forming a seventh circulation loop, namely the secondary heat pump cycle.

[0045] The terminal water supply pipeline 14 is connected to the other outlet of the secondary condenser 3-5. The other inlet of the secondary condenser 3-5 is connected to the first circulation pump 5-1 through the first valve 4-1. The first circulation pump 5-1 is connected to the terminal return water pipeline 13 to form a user-end circulation.

[0046] This invention can achieve heating and cooling requirements simultaneously with photovoltaic power generation by adjusting the circulation state of the heat pump, such as the heating / cooling cycle of the primary heat pump, the start / stop status of the secondary heat pump, and the opening and closing of various valves. It features single-stage / dual-stage switching for heating when heating is needed in winter, and cooling as required in summer. It can also utilize the heat pump to remove the waste heat generated by the photovoltaic modules in a timely manner, alleviating the phenomenon of reduced power generation efficiency caused by excessively high photovoltaic module temperatures. Furthermore, it can utilize solar energy to increase the evaporation temperature of the heat pump, improving the system's thermal performance, thereby achieving the advantages of complementary clean energy sources and cascaded utilization.

[0047] In this invention, a portion of the refrigerant is pre-cooled at the auxiliary electronic expansion valve 2-10, and then subcooled by the economizer 2-8 in the main circuit. The primary receiver 2-7 and the secondary receiver 3-6 are specifically designed to store liquid refrigerant, providing the required liquid supply for the heat pump system cycle and ensuring stable operation. The main function of the receiver in the heat pump system is to store refrigerant. Generally, receivers can be divided into high-pressure circulating receivers and low-pressure circulating receivers. Storing the liquid component of the refrigerant prevents excessive refrigerant accumulation in the condenser, which reduces the heat transfer area and effectively lowers the condenser load. It also provides a continuous supply of refrigerant to the evaporator, allowing any incompletely cooled refrigerant to be cooled again to a completely liquid state. The receiver also acts as a liquid seal, preventing gas from entering the low-pressure compressor and causing liquid slugging. Liquid slugging mainly occurs in reciprocating compressors, where liquid refrigerant (or lubricant) is drawn into the compressor, causing abnormal impact accidents.

[0048] This utility model features a primary gas-liquid separator 2-4 and a secondary gas-liquid separator 3-3 for gas-liquid separation, removing liquid entering the compressor to prevent lubricating oil or refrigerant from being sucked into the compressor inlet, causing liquid slugging and damaging internal compressor components. The fundamental function of a gas-liquid separator in a heat pump or refrigeration system is to separate and retain the liquid returning to the gas pipe, regulating flow and preventing liquid slugging in the compressor. Therefore, the gas-liquid separator can temporarily store excess refrigerant liquid and prevent excess refrigerant from flowing into the compressor crankcase and causing oil dilution. During the separation process, refrigerated oil is also separated and stored at the bottom. An oil filter screen with holes at the outlet pipe and bottom of the gas-liquid separator allows the refrigerated oil to return to the compressor, effectively preventing oil shortage. The gas-liquid separator has an internal U-shaped bend design with a protective mesh and small hole assembly to prevent foreign objects and dirt from affecting the separator's operation.

[0049] The function of the economizer 2-8 in this invention is to exchange heat between a portion of the refrigerant, after it has been throttled, depressurized, and cooled by the auxiliary expansion valve, and the high-pressure liquid refrigerant exiting the condenser. This process subcools a portion of the high-pressure liquid refrigerant, which then vaporizes and returns to the compressor to recycle. The subcooled refrigerant, after being depressurized and cooled by the main electronic expansion valve through the economizer, enters the evaporator to participate in the cycle. The economizer stabilizes the liquid refrigerant through expansion refrigeration, thereby improving system capacity and efficiency.

[0050] The first filter 2-3, the second filter 2-12, the third filter 3-2, and the fourth filter 3-8 of this utility model are components for filtering impurities in the system. They are mainly installed on both sides of the electronic expansion valve or capillary tube of the unit. The purpose is to prevent impurities in the system from clogging the electronic expansion valve and causing it to malfunction.

[0051] This utility model's dryer filter 2-9 is used to absorb moisture in the system, filter out impurities, and prevent ice blockage and dirt blockage in the system pipelines. Since the electronic expansion valve and capillary tube are the most easily blocked parts of the system, the dryer filter is usually installed between the condenser and the throttling device.

[0052] To achieve automatic control, the first valve 4-1, the second valve 4-2, the third valve 4-3, the fourth valve 4-4, and the fifth valve 4-5 are all electric valves.

[0053] Furthermore, check valves 16 are installed on both the seventh pipe 7 and the eighth pipe 8.

[0054] Furthermore, an electric heater is installed inside the buffer tank 15.

[0055] The working mode of this utility model is as follows:

[0056] See Figure 1and Figure 2 In the solar thermal power supply primary heat pump heating mode: start the first circulation pump 5-1 and the second circulation pump 5-2, and stop the operation of the third circulation pump 5-3; open the second valve 4-2 and the fourth valve 4-4, and close the first valve 4-1, the third valve 4-3 and the fifth valve 4-5; start the primary heat pump and stop the secondary heat pump. At this time, the first circulation loop, the third circulation loop and the sixth circulation loop participate in the circulation.

[0057] When the solar thermal power supply's primary heat pump is in operation, the antifreeze working fluid circulates between the collector refrigerant pipe 1-2 and the primary evaporator 2-1 via the first pipe 1, the second pipe 2, the fourth valve 4-4, and the second circulation pump 5-2. The low-temperature, low-pressure refrigerant gas, after absorbing heat in the primary evaporator 2-1, sequentially passes through the four-way reversing valve 2-2, the first filter 2-3, and the primary gas-liquid separator 2-4 before entering the primary compressor 2-5 to be heated and pressurized into a high-temperature, high-pressure gas. It then enters the primary condenser 2-6 to release heat and cool down into a low-temperature, high-pressure liquid. Next, it sequentially passes through the receiver 2-7, the economizer 2-8, and the dryer filter 2-9 before entering the main electronic expansion valve 2-11 for throttling and expansion into a low-temperature, low-pressure liquid. Finally, it returns to the primary evaporator 2-1 to absorb heat and complete the cycle. The low-temperature hot water in the buffer tank 15 enters the first-stage condenser 2-6 through the tenth pipe 10 and is heated to the required temperature. Under the action of the first circulation pump 5-1, it enters the user terminal through the sixth pipe 6 and the terminal water supply pipe 14 for heating. Then, it returns to the buffer tank 2-1 through the terminal return water pipe 13, the second valve 4-2 and the twelfth pipe 12 to complete the circulation.

[0058] See Figure 1 and Figure 3 In the first-stage heat pump cooling mode: the first circulation pump 5-1 and the second circulation pump 5-2 are started, and the third circulation pump 5-3 is stopped; the second valve 4-2 and the fourth valve 4-4 are opened, and the first valve 4-1, the third valve 4-3 and the fifth valve 4-5 are closed; the first-stage heat pump (cooling cycle) is started, and the second-stage heat pump is stopped; at this time, the first circulation loop, the fourth circulation loop and the sixth circulation loop participate in the cycle.

[0059] When the primary heat pump is running, the antifreeze working fluid circulates between the collector refrigerant pipe 1-2 and the primary evaporator 2-1 through the first pipe 1, the second pipe 2, the fourth valve 4-4, and the second circulation pump 5-2. After releasing heat in the first-stage evaporator (acting as a condenser) 2-1, the high-pressure, low-temperature refrigerant liquid passes through the second filter 2-12. Part of it is throttled and depressurized by the main electronic expansion valve 2-11, then passes through the dryer filter 2-9, economizer 2-8, and first-stage receiver 2-7 before connecting to the first-stage condenser (acting as an evaporator) 2-6. The other part is throttled by the capillary check valve 2-13 and capillary 2-14 before connecting to the first-stage receiver 2-7. The low-temperature, low-pressure refrigerant liquid then enters the first-stage condenser (acting as an evaporator) 2-6 to absorb heat and become a low-temperature, low-pressure gas. It then passes through the four-way reversing valve 2-2, the first filter 2-3, and the first-stage gas-liquid separator 2-4 before entering the first-stage compressor 2-5 to be heated and pressurized into a high-temperature, high-pressure refrigerant gas. Finally, it passes through the four-way reversing valve 2-2 and enters the first-stage evaporator (acting as a condenser) 2-1 to release heat and form a cycle. The low-temperature water in the buffer water tank 15 enters the first-stage condenser (acting as an evaporator) 2-6 through the tenth pipe 10 and is cooled to the required temperature. Under the action of the first circulation pump 5-1, it enters the user terminal for cooling through the sixth pipe 6 and the terminal water supply pipe 14 in sequence. Then, it returns to the buffer water tank 2-1 through the terminal return water pipe 13, the second valve 4-2 and the twelfth pipe 12 to complete the circulation.

[0060] See Figure 1 and Figure 4 In the two-stage heat pump heating mode of solar thermal power supply: start the first circulation pump 5-1 and the second circulation pump 5-2, and stop the operation of the third circulation pump 5-3; open the first valve 4-1, the third valve 4-3 and the fifth valve 4-5, and close the second valve 4-2 and the fourth valve 4-4; start the second-stage heat pump and stop the operation of the first-stage heat pump; at this time, the second circulation loop and the seventh circulation loop participate in the circulation.

[0061] When the solar thermal two-stage heat pump is operating, the antifreeze working fluid circulates between the collector refrigerant pipe 1-2 and the secondary evaporator 3-1 via the first pipe 1, the third pipe 3, the fifth valve 4-5, the fourth pipe 4, the fifth pipe 5, the third valve 4-3, and the second circulation pump 5-2. The low-temperature, low-pressure refrigerant gas, after absorbing heat in the secondary evaporator 3-1, passes sequentially through the third filter 3-2 and the secondary gas-liquid separator 3-3 into the secondary compressor 3-4, where it is heated and pressurized into a high-temperature, high-pressure gas. It then enters the secondary condenser 3-5, releasing heat and cooling into a low-temperature, high-pressure liquid. It then passes sequentially through the receiver 3-6 and the fourth filter 3-7 into the secondary electronic expansion valve 3-8, where it expands into a low-temperature, low-pressure liquid. Finally, it returns to the secondary evaporator 3-1 to absorb heat and complete the cycle. The terminal return water pipe 13, under the action of the first circulation pump 5-1, enters the secondary condenser 3-5 through the first valve 4-1 to absorb heat. After being heated to the required temperature, it travels to the user's terminal via the terminal return water pipe 14.

[0062] See Figure 1 and Figure 5 Two-stage heat pump circulation mode: Start the first circulation pump 5-1, the second circulation pump 5-2 and the third circulation pump 5-3; open the first valve 4-1 and the fourth valve 4-4, and close the second valve 4-2, the third valve 4-3 and the fifth valve 4-5; start the operation of the first-stage heat pump and start the operation of the second-stage heat pump. At this time, the first circulation loop, the third circulation loop, the fifth circulation loop and the seventh circulation loop participate in the circulation.

[0063] During the two-stage heat pump cycle, the antifreeze working fluid circulates between the refrigerant pipe 1-2 of the solar collector and the first-stage evaporator 2-1 through the first pipe 1, the second pipe 2, the fourth valve 4-4, and the second circulation pump 5-2. The low-temperature, low-pressure refrigerant gas, after absorbing heat in the first-stage evaporator 2-1, sequentially passes through the four-way reversing valve 2-2, the first filter 2-3, and the first-stage gas-liquid separator 2-4 before entering the first-stage compressor 2-5 to be heated and pressurized into a high-temperature, high-pressure gas. It then enters the first-stage condenser 2-6 to release heat and cool down into a low-temperature, high-pressure liquid. Next, it sequentially passes through the receiver 2-7, the economizer 2-8, and the dryer filter 2-9 before entering the main circuit electronic expansion valve 2-11 for throttling and expansion into a low-temperature, low-pressure liquid. Finally, it returns to the first-stage evaporator 2-1 to absorb heat and complete the cycle. The low-temperature hot water in buffer tank 15 enters the primary condenser 2-6 through the tenth pipe 10 and is heated to the required temperature. Under the action of the third circulation pump 5-3, it sequentially enters the second inlet of the secondary evaporator 3-1 through the sixth pipe 6 and the eighth pipe 8, and then returns to the buffer tank 2-1 through the second outlet of the secondary evaporator 3-1 and the ninth pipe 9 to complete the cycle. The low-temperature, low-pressure refrigerant gas that absorbs heat in the secondary evaporator 3-1 sequentially passes through the third filter 3-2 and the secondary gas-liquid separator 3-3 to enter the secondary compressor 3-4, where it is heated and pressurized into a high-temperature, high-pressure gas. Then, it enters the secondary condenser 3-5 to release heat and cool down into a low-temperature, high-pressure liquid. It then sequentially passes through the liquid receiver 3-6 and the fourth filter 3-7 to enter the secondary electronic expansion valve 3-8 for throttling and expansion into a low-temperature, low-pressure liquid, and finally returns to the secondary evaporator 3-1 to absorb heat and complete the cycle. The terminal return water management 13, under the action of the first circulation pump 5-1, enters the secondary condenser 3-5 through the first valve 4-1 to absorb heat. After being heated to the required temperature, it goes to the user terminal through the terminal water supply pipe 14.

[0064] This invention allows for the production of water at different temperatures under varying ambient temperatures by adjusting the heating / cooling cycle and start / stop status of the primary heat pump, the start / stop status of the secondary heat pump, and the on / off status of various valves. This invention offers the advantage of single-stage / dual-stage switching for heating in winter and providing heating and cooling as needed in summer.

[0065] The above description is merely a specific embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this utility model should be included within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the protection scope of the claims.

Claims

1. A photovoltaic-thermal two-stage heat pump system, characterized in that, This includes photovoltaic thermal systems, primary heat pump systems, buffer water tank systems, and secondary heat pump systems; The photovoltaic thermal system includes a photovoltaic panel. A refrigerant pipe for a collector is attached to the back of the photovoltaic panel. The outlet of the refrigerant pipe for the collector is divided into two paths. One path connects to one side inlet of the first-stage evaporator through a first pipe and a second pipe in sequence. The outlet of the first-stage evaporator is connected to the refrigerant inlet of the collector through a fourth valve and a second circulation pump in sequence. The other path connects to the first inlet of the second-stage evaporator through a first pipe, a third pipe, a fifth valve, and a fourth pipe in sequence. The first outlet of the second-stage evaporator is connected to the refrigerant inlet of the collector through a fifth pipe, a third valve, and a second circulation pump in sequence. The primary heat pump system includes a primary heat pump heating cycle system and a primary heat pump cooling cycle system. The primary heat pump heating cycle system includes a primary evaporator. The other outlet of the primary evaporator is connected to a primary compressor via a four-way reversing valve, a first filter, and a gas-liquid separator. The primary compressor is connected to one inlet of a primary condenser via a four-way reversing valve. The one outlet of the primary condenser is connected to one inlet of a primary economizer via a primary liquid receiver. The one outlet of the primary economizer is divided into two paths after passing through a dryer filter: a main path and a make-up gas path. The make-up gas path is connected to the other inlet of the primary economizer via an auxiliary electronic expansion valve. The other outlet of the primary economizer is connected to the make-up gas port of the primary compressor. The main path is connected to the other inlet of the primary evaporator via a dryer filter, a main electronic expansion valve, and a second filter. The first-stage heat pump refrigeration cycle system includes a first-stage evaporator. The outlet of the first-stage evaporator is split into two paths after passing through a second filter. One path is connected to one side inlet of the first-stage condenser through a first-stage main electronic expansion valve, a dryer filter, an economizer, and a liquid receiver in sequence. The other path is connected to the liquid receiver through a capillary check valve and a capillary tube in sequence. One side outlet of the first-stage condenser is connected to the inlet of the first-stage compressor through a four-way reversing valve, a first filter, and a first-stage gas-liquid separator. The outlet of the first-stage compressor is connected to the other side inlet of the first-stage evaporator through a four-way reversing valve. The buffer water tank system includes a buffer water tank. The outlet of the buffer water tank is connected to the other inlet of the first-stage condenser via a tenth pipe. The other outlet of the first-stage condenser is divided into two paths. One path is connected to the second inlet of the second-stage evaporator via a sixth pipe, a third circulation pump, and an eighth pipe. The second outlet of the second-stage evaporator is connected to the first inlet of the buffer water tank via a ninth pipe. The other path is connected to the terminal water supply line via a sixth pipe and a seventh pipe. The terminal return water line is connected to the second inlet of the buffer water tank via a first circulation pump, an eleventh pipe, a second valve, and a twelfth pipe. The secondary heat pump system includes a secondary evaporator. The third outlet of the secondary evaporator is connected to the inlet of the secondary compressor via a third filter and a secondary gas-liquid separator. The outlet of the secondary compressor is connected to one side inlet of the secondary condenser. The one side outlet of the secondary condenser is connected to the third inlet of the secondary evaporator via a secondary liquid receiver, a fourth filter, and a secondary electronic expansion valve. The terminal water supply pipeline is connected to the other outlet of the secondary condenser, and the other inlet of the secondary condenser is connected to the first circulation pump through the first valve.

2. The photovoltaic-thermal dual-stage heat pump system according to claim 1, characterized in that, The collector refrigerant pipe is equipped with heat dissipation fins, and the working fluid of the collector refrigerant pipe is antifreeze. The collector refrigerant pipe and the photovoltaic panel transfer heat through the antifreeze.

3. The photovoltaic-thermal dual-stage heat pump system according to claim 2, characterized in that, The primary evaporator is a dual-channel plate heat exchanger; the secondary evaporator is a three-channel plate heat exchanger.

4. The photovoltaic-thermal dual-stage heat pump system according to claim 3, characterized in that, The working fluid in one channel of the three-channel plate heat exchanger is antifreeze, the working fluid in another channel is water, and the working fluid in the third channel is fluorine.

5. The photovoltaic-thermal dual-stage heat pump system according to any one of claims 1-4, characterized in that, The first valve, the second valve, the third valve, the fourth valve, and the fifth valve are all electric valves.

6. The photovoltaic-thermal dual-stage heat pump system according to claim 5, characterized in that, Both the seventh and eighth pipes are equipped with check valves.

7. The photovoltaic-thermal dual-stage heat pump system according to claim 6, characterized in that, The buffer tank is equipped with an electric heater.

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