Photovoltaic heat pump system and standing start control method

Abstract

The application provides a photovoltaic heat pump system and a standing start control method, and relates to the technical field of heat pump units. The photovoltaic heat pump system comprises a compressor, a crank heating belt, a double-pipe heat exchanger, an electronic expansion valve, a fin heat exchanger, a photovoltaic panel, a fluorine pump, a four-way valve and a controller. The first branch and the second branch are arranged in parallel between the photovoltaic panel and the fin heat exchanger, the fluorine pump is arranged on the first branch, and the one-way valve is arranged on the second branch. The standing start control method of the photovoltaic heat pump system is as follows: when the standby time is less than the first threshold value and the environmental temperature is lower than the threshold value, the crank heating belt is started to heat the compressor; when the standby time exceeds the first threshold value, the crank heating belt is started or the crank heating belt and the fluorine pump are simultaneously started according to the comparison result of the fin heat exchanger temperature and the preset threshold value. According to the system standing state and the environmental conditions, the circulating heating of the migrated liquid refrigerant is realized, and the first start safety of the photovoltaic heat pump system is improved.

Description

Technical Field

[0001] This invention belongs to the technical field of heat pump units, and more specifically relates to a photovoltaic heat pump system and a static start-up control method. Background Technology

[0002] A photovoltaic heat pump system is an integrated energy device that combines photovoltaic power generation with heat pump technology, and is widely used in building heating, cooling, and domestic hot water supply. A traditional integrated dual-generation heat pump unit mainly consists of a compressor, finned heat exchanger, coaxial heat exchanger, electronic expansion valve, four-way reversing valve, and water pump. These units can typically operate stably within a wide range of ambient temperatures (e.g., -35℃ to 53℃) and water temperatures (e.g., 5℃ to 60℃), meeting users' cooling and heating needs in different seasons.

[0003] In practical applications, there is a time lag between the installation season and the season when photovoltaic heat pump units are put into operation. For example, the unit may be installed in the summer but not started until the winter heating season. During this period, the unit will experience a standby and static state for several months. Due to the physical property of refrigerant (coolant) migrating with changes in ambient temperature, during the long period of standby, the refrigerant will gradually migrate and accumulate in large quantities in the relatively low-temperature finned heat exchanger. When the unit is started for the first time in the cold season, a large amount of liquid refrigerant will be drawn into the compressor along with the gaseous refrigerant. Liquid refrigerant is incompressible, and its entry into the compressor cylinder will cause liquid slugging, which in severe cases can damage the compressor valves, wear bearings, or even render the entire unit unusable, causing irreversible damage to the compressor and significantly affecting the unit's service life and operational reliability.

[0004] Existing methods generally address the aforementioned problems by adding a crankshaft heating belt around the compressor. Its working principle is to preheat the oil sump at the bottom of the compressor using an electric heating belt before the unit is idle or started, causing the refrigerant dissolved in the lubricating oil to evaporate and escape. Simultaneously, this increases the compressor cavity temperature, thereby reducing the impact of liquid refrigerant on the compressor to some extent.

[0005] In practical applications, due to the limited output power of the crankshaft heating belt, its heating capacity is far from sufficient to offset the heat absorbed by the refrigerant during the evaporation process. Especially when the ambient temperature is low and the refrigerant migration is large, the preheating effect of the crankshaft heating belt is weak, making it difficult to fundamentally solve the problem of a large amount of liquid refrigerant flowing back to the compressor. This makes it impossible to effectively guarantee the safety of the photovoltaic heat pump system during its first start-up after a long period of inactivity. Summary of the Invention

[0006] To address the issue of poor start-up safety in existing photovoltaic heat pump systems due to the migration of liquid refrigerant to the finned heat exchanger after long-term quiescence, this invention provides a photovoltaic heat pump system and a quiescence start-up control method that circulates and heats the migrated liquid refrigerant, thereby improving the safety of the photovoltaic heat pump system during its first start-up.

[0007] To achieve the above-mentioned technical effects, the technical solution of the present invention is as follows: This invention provides a photovoltaic heat pump system, comprising: a compressor, a crankshaft heating belt, a shell-and-tube heat exchanger, an electronic expansion valve, a finned heat exchanger, a photovoltaic panel, a refrigerant pump, a four-way valve, and a controller; The compressor's exhaust port is connected to the first port of the four-way valve, and the compressor's intake port is connected to the second port of the four-way valve; the compressor is equipped with a crankshaft heating belt; the third port of the four-way valve is connected to the first port of the shell-and-tube heat exchanger, and the fourth port of the four-way valve is connected to the first port of the finned heat exchanger; the second port of the shell-and-tube heat exchanger is connected to the first port of the electronic expansion valve; the second port of the electronic expansion valve is connected to the second port of the finned heat exchanger. The photovoltaic panel and the finned heat exchanger are connected in parallel via a first branch and a second branch; the inlet of the photovoltaic panel is connected to the second port of the finned heat exchanger via the first branch, and a fluorine pump is provided on the first branch; the outlet of the photovoltaic panel is connected to the first port of the finned heat exchanger via the second branch. The crankshaft heating belt and the fluorine pump are respectively connected to the controller.

[0008] Furthermore, the first branch is also equipped with a solenoid valve; one end of the solenoid valve is connected to the second port of the finned heat exchanger; the other end of the solenoid valve is connected to the refrigerant pump; the solenoid valve and the controller are connected for control. Furthermore, the second branch is equipped with a one-way valve, the inlet of which is connected to the outlet of the photovoltaic panel, and the outlet of which is connected to the first interface of the finned heat exchanger.

[0009] Furthermore, it also includes a gas-liquid separator, the inlet of which is connected to the second port of the four-way valve; the outlet of which is connected to the suction port of the compressor.

[0010] Furthermore, it also includes: a first temperature sensor, a second temperature sensor, and a third temperature sensor; the first temperature sensor is disposed at the lowest flow path of the finned heat exchanger and is used to detect the temperature at the bottom of the finned heat exchanger; the second temperature sensor is disposed at the top of the finned heat exchanger and is used to detect the ambient temperature; the third temperature sensor is disposed on the surface of the photovoltaic panel and is used to detect the surface temperature of the photovoltaic panel; the first temperature sensor, the second temperature sensor, and the third temperature sensor are electrically connected to the controller.

[0011] Furthermore, it also includes a distributor, a gas collection pipe, a first tee, and a second tee; The first port of the first tee is connected to the finned heat exchanger, the second port of the first tee is connected to the distributor outlet, and the third port of the first tee is connected to the solenoid valve. The inlet of the distributor is connected to the second port of the electronic expansion valve; the outlet of the distributor is also connected to the finned heat exchanger. The first port of the second three-way valve is connected to the finned heat exchanger, the second port of the second three-way valve is connected to the inlet of the gas collecting pipe, and the third port of the second three-way valve is connected to the check valve. The inlet of the gas collecting pipe is also connected to the finned heat exchanger; the outlet of the gas collecting pipe is connected to the fourth port of the four-way valve.

[0012] Furthermore, the photovoltaic heat pump system has a cooling mode, a heating mode, and a static mode; In the cooling mode and heating mode, the controller controls the solenoid valve to close, the refrigerant pump to stop running, the first branch is disconnected, and the second branch is not connected; In the static mode, the controller controls the solenoid valve to open, the fluorine pump to start, and the second branch to be activated.

[0013] The present invention also provides a static start-up control method for a photovoltaic heat pump system, comprising the following steps: S1: Use the controller to record the standby time of the photovoltaic heat pump system and read the temperature of the finned heat exchanger, the ambient temperature and the photovoltaic panel temperature; S2: Determine whether the standby time of the photovoltaic heat pump system is less than the first threshold. If the standby time is less than the first threshold, proceed to step S3; otherwise, proceed to step S4. S3: Determine whether the ambient temperature is lower than the preset ambient temperature threshold. If the ambient temperature is lower than the preset temperature threshold, the controller controls the crankshaft heating belt to start and heat the compressor; otherwise, the photovoltaic heat pump system is in normal standby mode, the electronic expansion valve is closed, and the shell-and-tube heat exchanger and four-way valve are not started. S4: Determine whether the temperature of the finned heat exchanger is lower than the preset finned heat exchanger temperature threshold. If yes, proceed to step S5; otherwise, the controller controls the crankshaft heating belt to start and heat the compressor. S5: Determine if the temperature of the photovoltaic panel is lower than that of the finned heat exchanger. If so, the controller starts the crankshaft heating belt to heat the compressor; otherwise, the controller starts the crankshaft heating belt to heat the compressor; the refrigerant pump starts, and the four-way valve and electronic expansion valve open.

[0014] Furthermore, the controller activates the crankshaft heating belt to heat the compressor as follows: Step 1: The controller activates the crankshaft heating belt to heat the compressor; Step 2: When the crankshaft heating belt reaches the first preset time, the controller controls the crankshaft heating belt to stop heating; Step 3: When the crankshaft heating belt stops for the second preset time, return to Step 1 until the photovoltaic heat pump system receives the start command.

[0015] Furthermore, the process of starting the fluorine pump and opening the four-way valve and electronic expansion valve is as follows: Step 1: The controller controls the opening of the four-way valve, electronic expansion valve, and solenoid valve, and starts the refrigerant pump; Step 2: During the operation of the refrigerant pump, monitor the temperature difference between the finned heat exchanger temperature T2 and the ambient temperature T1. When the temperature difference exceeds the preset temperature difference threshold, the controller will stop the refrigerant pump in advance and close the solenoid valve; otherwise, proceed to step three. Step 3: After the refrigerant pump has been running for the third preset time, the controller will stop the refrigerant pump and close the solenoid valve. Step 4: When the refrigerant pump stops for the fourth preset time, the controller opens the solenoid valve and starts the refrigerant pump. Step 5: When the refrigerant pump has been running for five preset times, the controller will stop the refrigerant pump and close the solenoid valve. Step Six: Repeat steps four and five until the photovoltaic heat pump system receives a start command.

[0016] Compared with existing technologies, the beneficial effects of this method are: This invention provides a photovoltaic heat pump system and a static start-up control method. The photovoltaic heat pump system includes a compressor, a crankshaft heating belt, a shell-and-tube heat exchanger, an electronic expansion valve, a finned heat exchanger, a photovoltaic panel, a refrigerant pump, a four-way valve, and a controller. A first branch and a second branch are connected in parallel between the photovoltaic panel and the finned heat exchanger. The refrigerant pump is installed on the first branch, and a one-way valve is installed on the second branch. In the static start-up control method of the photovoltaic heat pump system, when the standby time is less than a first threshold and the ambient temperature is lower than the threshold, the controller controls the crankshaft heating belt to start, heating the compressor. When the standby time exceeds the first threshold, based on the comparison between the finned heat exchanger temperature and a preset threshold, it is determined whether to execute the controller to control the crankshaft heating belt to start, or the controller to control the crankshaft heating belt to start, heating the compressor; the refrigerant pump starts, and the four-way valve and the electronic expansion valve open. This method can select the optimal start-up based on the system's static state and environmental conditions, circulating and heating the migrating liquid refrigerant, thus improving the safety of the photovoltaic heat pump system's initial start-up. Attached Figure Description

[0017] Figure 1 This diagram shows the overall structure of the photovoltaic heat pump system proposed in this embodiment of the invention. Figure 2 This diagram illustrates the connection between the first and second branches of the photovoltaic heat pump system proposed in this embodiment of the invention. Figure 3 This diagram illustrates the connection of the controller for the photovoltaic heat pump system proposed in this embodiment of the invention. Figure 4 This is a flowchart illustrating the static start-up control method for a photovoltaic heat pump system proposed in this embodiment of the invention.

[0018] 1. Compressor; 2. Crankshaft heating belt; 3. Shell-and-tube heat exchanger; 4. Electronic expansion valve; 5. Finned heat exchanger; 6. Photovoltaic panel; 7. Refrigerant pump; 8. Four-way valve; 9. Controller; 10. Solenoid valve; 11. Check valve; 12. Gas-liquid separator; 13. First temperature sensor; 14. Second temperature sensor; 15. Third temperature sensor; 16. Distributor; 17. Gas collection pipe; 18. First tee; 19. Second tee Detailed Implementation The accompanying drawings are for illustrative purposes only and should not be construed as limiting the scope of this patent. To better illustrate this embodiment, some parts of the accompanying drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions; It is understandable to those skilled in the art that some well-known details may be omitted from the accompanying drawings.

[0019] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0020] The positional relationships depicted in the accompanying drawings are for illustrative purposes only and should not be construed as limiting this patent. Example 1 This embodiment provides a photovoltaic heat pump system, such as Figure 1 The overall structure diagram of the photovoltaic heat pump system shown includes: compressor 1, crankshaft heating belt 2, shell and tube heat exchanger 3, electronic expansion valve 4, finned heat exchanger 5, photovoltaic panel 6, fluorine pump 7, four-way valve 8, and controller 9. The exhaust port of the compressor 1 is connected to the first port of the four-way valve 8, and the intake port of the compressor 1 is connected to the second port of the four-way valve 8; the compressor 1 is equipped with a crankshaft heating belt 2; the third port of the four-way valve 8 is connected to the first port of the shell-and-tube heat exchanger 3, and the fourth port of the four-way valve 8 is connected to the first port of the finned heat exchanger 5; the second port of the shell-and-tube heat exchanger 3 is connected to the first port of the electronic expansion valve 4; the second port of the electronic expansion valve 4 is connected to the second port of the finned heat exchanger 5. The photovoltaic panel 6 and the finned heat exchanger 5 are connected in parallel with a first branch and a second branch; the inlet of the photovoltaic panel 6 is connected to the second port of the finned heat exchanger 5 through the first branch, and a fluorine pump 7 is provided on the first branch; the outlet of the photovoltaic panel 6 is connected to the first port of the finned heat exchanger 5 through the second branch.

[0021] The crankshaft heating belt 2 and the fluorine pump 7 are respectively connected to the controller 9.

[0022] In the photovoltaic heat pump system proposed in this embodiment, compressor 1 serves as the power core, compressing the refrigerant and driving its circulation. A four-way valve 8 switches between cooling and heating modes by changing the connection direction of its interface. The shell-and-tube heat exchanger 3 and the finned heat exchanger 5 serve as the terminal components for heat exchange with water and air, respectively. The finned heat exchanger 5 is a location where refrigerant is prone to migration and accumulation during standby. The electronic expansion valve 4 is used for throttling and pressure reduction, regulating the refrigerant flow rate. A crankshaft heating belt 2 is located at the bottom of compressor 1 to preheat the compressor during low-temperature standby, preventing liquid refrigerant accumulation. The photovoltaic panel 6 serves as a solar energy collection element, providing a clean heat source for the refrigerant in standby mode. The refrigerant pump 7 starts under the control of controller 9, creating an independent circulation loop between the finned heat exchanger 5 and the photovoltaic panel 6, transporting the liquid refrigerant that has migrated and accumulated in the finned heat exchanger to the photovoltaic panel for heating and evaporation. Controller 9, as the system's control center, intelligently decides and controls the start-up, shutdown, and operation cycles of the crankshaft heater 2 and the refrigerant pump 7 based on parameters such as standby time and ambient temperature. The coordinated operation of these components effectively prevents liquid refrigerant from entering the compressor and causing liquid slugging damage during the first start-up after a long period of inactivity, significantly improving the operational safety and reliability of the photovoltaic heat pump system. Simultaneously, it fully utilizes solar energy to achieve energy conservation and consumption reduction.

[0023] In this embodiment, the four-way valve 8 has four ports, namely port D, port C, port E and port S; wherein, the first port corresponds to port D of the four-way valve; the second port corresponds to port S of the four-way valve; the third port corresponds to port C of the four-way valve; and the fourth port corresponds to port E of the four-way valve.

[0024] In this embodiment, the first branch is also equipped with a solenoid valve 10; one end of the solenoid valve 10 is connected to the second port of the finned heat exchanger 5; the other end of the solenoid valve 10 is connected to the refrigerant pump 7. The solenoid valve 10 and the controller 9 are connected for control.

[0025] The second branch is equipped with a one-way valve 11. The inlet of the one-way valve 11 is connected to the outlet of the photovoltaic panel 6, and the outlet of the one-way valve 11 is connected to the first interface of the finned heat exchanger 5.

[0026] In this embodiment, the solenoid valve 10 is installed on the first branch, connecting the second port of the finned heat exchanger 5 to the refrigerant pump 7, and electrically connected to the controller 9. It is used to open or close the first branch under the control of the controller 9, thereby precisely controlling the start and stop timing of the auxiliary circulation loop, ensuring that the refrigerant pump circulation is started only when the conditions are met, and avoiding unnecessary energy loss.

[0027] One-way valve 11 is installed on the second branch to ensure that the refrigerant can only flow in one direction in the circuit, that is, after flowing out of the photovoltaic panel 6, it must return to the finned heat exchanger 5, to prevent the high-temperature refrigerant from flowing back to the photovoltaic panel and causing heat loss or reverse flow that interferes with the cycle efficiency.

[0028] The synergistic effect of solenoid valve 10 and check valve 11 enables the auxiliary circulation loop to achieve directional and controllable refrigerant flow, ensuring that the liquid refrigerant migrating to the bottom of finned heat exchanger 5 can be accurately delivered to photovoltaic panel 6 to absorb solar energy for heating and evaporation. At the same time, it avoids the backflow of heated refrigerant, greatly improves the static heating efficiency, and ensures the safety of the first start-up after the system has been static for a long time.

[0029] The photovoltaic heat pump system also includes a gas-liquid separator 12, the inlet of which is connected to the second port of the four-way valve 8; the outlet of which is connected to the suction port of the compressor 1.

[0030] The photovoltaic heat pump system also includes: a first temperature sensor 13, a second temperature sensor 14, and a third temperature sensor 15; the first temperature sensor 13 is located at the lowest flow path of the finned heat exchanger 5 and is used to detect the temperature at the bottom of the finned heat exchanger; the second temperature sensor 14 is located at the top of the finned heat exchanger 5 and is used to detect the ambient temperature; the third temperature sensor 15 is located on the surface of the photovoltaic panel 6 and is used to detect the surface temperature of the photovoltaic panel; the first temperature sensor 13, the second temperature sensor 14, and the third temperature sensor 15 are electrically connected to the controller 9.

[0031] In this embodiment, the first temperature sensor 13 is a coil temperature sensor, installed on the surface of the lowest flow path coil of the finned heat exchanger 5, used to detect the bottom temperature of the finned heat exchanger. The second temperature sensor 14 is an ambient temperature sensor, installed on the outer surface of the unit near the top of the finned heat exchanger 5, used to detect the ambient temperature. The third temperature sensor is a photovoltaic panel temperature sensor, installed on the back of the photovoltaic panel 6 near the heat exchange pipeline, used to detect the surface temperature of the photovoltaic panel. The three temperature sensors are electrically connected to the controller 9. The controller 9 performs graded control based on the standby time h and the temperature data T1, T2, and T3. This invention, through the coordinated detection of the three temperature sensors, achieves accurate judgment of low ambient temperature conditions, photovoltaic panel heating capacity, and finned heat exchanger temperature recovery, ensuring that the refrigerant pump circulation is activated only when there is effective sunlight and it is truly necessary, avoiding ineffective operation.

[0032] like Figure 2 The diagram showing the connection between the first and second branches is provided. The photovoltaic heat pump system also includes a distributor 16, a gas collection pipe 17, a first tee 18, and a second tee 19. The first port of the first tee 18 is connected to the finned heat exchanger 5, the second port of the first tee 18 is connected to the outlet of the distributor 16, and the third port of the first tee 18 is connected to the solenoid valve 10. The inlet of the distributor 16 is connected to the second port of the electronic expansion valve 4; the outlet of the distributor 16 is also connected to the finned heat exchanger 5. The first port of the second three-way valve 19 is connected to the finned heat exchanger 5, the second port of the second three-way valve 19 is connected to the inlet of the gas collecting pipe 17, and the third port of the second three-way valve 19 is connected to the one-way valve 11. The inlet of the gas collecting pipe 17 is also connected to the finned heat exchanger 5; the outlet of the gas collecting pipe 17 is connected to the fourth port of the four-way valve 8.

[0033] For example, the dispenser is a brass dispenser.

[0034] In this embodiment, the distributor 16 is positioned between the electronic expansion valve 4 and the finned heat exchanger 5 to evenly distribute the throttled refrigerant into multiple flow paths of the finned heat exchanger, ensuring uniform heat exchange in each flow path. The gas collecting pipe 17 is positioned between the finned heat exchanger 5 and the four-way valve 8 to collect the refrigerant from each flow path outlet and deliver it to the four-way valve, ensuring smooth gas return. The three ports of the first three-way valve 18 are respectively connected to the inlet of the last flow path of the finned heat exchanger 5, the last outlet of the distributor 16, and the inlet of the solenoid valve 10, used to guide the refrigerant flowing out of the last flow path of the distributor into the auxiliary circulation loop in the static mode. The three ports of the second three-way valve 19 are respectively connected to the outlet of the last flow path of the finned heat exchanger 5, the last inlet of the gas collecting pipe 17, and the outlet of the one-way valve 11, used to recirculate the refrigerant heated by the photovoltaic panel 6 back into the gas collecting pipe and return it to the system. The above-mentioned components are designed so that the auxiliary circulation loop only circulates and heats the refrigerant in the last flow path of the finned heat exchanger. This ensures the heating effect and avoids excessive heat exchange load caused by a large amount of refrigerant passing through the photovoltaic panel at once. At the same time, the power consumption of the refrigerant pump is also controlled at a low level, achieving precise and efficient static heating.

[0035] In this embodiment, as Figure 3 The diagram shows the connection of the controller, which uses a microcontroller unit (MCU) and integrates digital output and analog input interfaces. The digital output interface is connected to the crankshaft heater, refrigerant pump, and solenoid valve via relays to control their start and stop. The analog input interface is connected to a first, second, and third temperature sensor to collect real-time data on ambient temperature T1, the bottom temperature of the finned heat exchanger T2, and the photovoltaic panel temperature T3. The first temperature sensor is installed on the outer surface of the unit near the top of the finned heat exchanger; the second temperature sensor is installed on the surface of the bottom flow coil of the finned heat exchanger; and the third temperature sensor is installed on the back of the photovoltaic panel near the heat exchange piping. The controller outputs control signals according to preset control logic based on the standby time and the collected temperature data.

[0036] When the photovoltaic heat pump system is powered on, the controller 9 reads the analog voltage signals output by the first temperature sensor 13, the second temperature sensor 14, and the third temperature sensor 15 through the interface according to a preset sampling period (e.g., every 100 milliseconds). The first temperature sensor 13, the second temperature sensor 14, and the third temperature sensor 15 are all negative temperature coefficient thermistors (NTCs), whose resistance decreases as the temperature increases; the controller 9 has a resistance-temperature lookup table or temperature calculation formula pre-stored inside.

[0037] After reading the analog voltage signals from each temperature sensor, controller 9 first calculates the resistance value of the current sensor based on the voltage divider circuit parameters. Then, it converts the resistance value into the corresponding temperature value by looking up a table or by calculation, which are recorded as: finned heat exchanger temperature T2, ambient temperature T1, and photovoltaic panel temperature T3. Controller 9 stores the read temperature data in its internal register.

[0038] Example 2 In this embodiment, the three modes of the photovoltaic heat pump system proposed in Embodiment 1 are described in detail.

[0039] In this embodiment, the photovoltaic heat pump system has a cooling mode, a heating mode, and a static mode; In the cooling mode and heating mode, the controller 9 controls the solenoid valve 10 to close, the refrigerant pump 7 to stop running, the first branch is disconnected, and the second branch is not connected; In the static mode, the controller 9 controls the solenoid valve 10 to open, the fluorine pump 7 to start, and the second branch to be connected.

[0040] In this embodiment, when the photovoltaic heat pump system is operating in heating mode, the controller 9 controls the solenoid valve 10 to close and the refrigerant pump 7 to stop operating. The refrigerant does not participate in the heat exchange of the photovoltaic panel 6, but only flows forward along the main circulation loop. The path is: compressor 1 exhaust port → four-way valve 8 D port → four-way valve 8 C port → shell-and-tube heat exchanger 3 → electronic expansion valve 4 → finned heat exchanger 5 → four-way valve 8 E port → four-way valve 8 S port → gas-liquid separator 12 → compressor 1 suction port. At this time, the shell-and-tube heat exchanger 3 acts as a condenser, releasing heat to the water side to achieve the heating function, and the finned heat exchanger 5 acts as an evaporator, absorbing heat from the air to complete the heating cycle.

[0041] When the system operates in cooling mode, controller 9 also controls solenoid valve 10 to close and refrigerant pump 7 to stop operating. The refrigerant flows in reverse along the main circulation loop: compressor 1 discharge port → four-way valve 8 D port → four-way valve 8 E port → finned heat exchanger 5 → electronic expansion valve 4 → shell-and-tube heat exchanger 3 → four-way valve 8 C port → four-way valve 8 S port → gas-liquid separator 12 → compressor 1 suction port. At this time, finned heat exchanger 5 acts as a condenser, releasing heat to the air, while shell-and-tube heat exchanger 3 acts as an evaporator, absorbing heat from the water side to achieve the cooling function. In both modes, solenoid valve 10 and refrigerant pump 7 do not operate, ensuring that the refrigerant flows only in the main circulation loop, guaranteeing that the unit meets the user's cooling or heating needs with maximum efficiency.

[0042] In this embodiment, when the photovoltaic heat pump system is in static mode, the controller 9 controls the solenoid valve 10 to open and the refrigerant pump 7 to start. Driven by the refrigerant pump 7, the refrigerant flows along the auxiliary circulation loop. Specifically, the flow direction is: outlet of the last flow path of the finned heat exchanger 5 → first interface of the second three-way valve 19 → third interface of the second three-way valve 19 → outlet of the one-way valve 11 → inlet of the one-way valve 11 → outlet of the photovoltaic panel 6 → internal heat exchange pipes of the photovoltaic panel 6 → inlet of the photovoltaic panel 6 → outlet of the refrigerant pump 7 → inlet of the refrigerant pump 7 → outlet of the solenoid valve 10 → inlet of the solenoid valve 10 → third interface of the first three-way valve 18 → first interface of the first three-way valve 18 → inlet of the last flow path of the finned heat exchanger 5, forming a complete circulation loop. During this process, the refrigerant absorbs solar energy and heats up to evaporate within the photovoltaic panel 6, heating and vaporizing the liquid refrigerant that has migrated and accumulated at the bottom of the finned heat exchanger 5. This prevents liquid refrigerant from entering the compressor and causing liquid slugging damage during the next system startup, achieving intelligent protection in static mode.

[0043] In this embodiment, the photovoltaic heat pump system uses controller 9 to intelligently control solenoid valve 10 and refrigerant pump 7, enabling flexible switching between three operating modes: In cooling and heating modes, controller 9 controls solenoid valve 10 to close and refrigerant pump 7 to stop, disconnecting the first branch and de-conducting the second branch. The refrigerant flows only along the main circulation loop. At this time, photovoltaic panel 6 does not participate in system heat exchange, ensuring the unit operates efficiently in a conventional manner to meet the user's cooling or heating needs. In standby mode, controller 9 controls solenoid valve 10 to open and refrigerant pump 7 to start, connecting the first branch and naturally connecting the second branch under the action of check valve 11. Driven by the refrigerant pump, the refrigerant enters photovoltaic panel 6 along the first branch to absorb solar energy for heating, and then returns to finned heat exchanger 5 via the second branch, forming an independent auxiliary circulation loop. This loop circulates and heats the liquid refrigerant that has migrated and accumulated in finned heat exchanger 5, effectively preventing liquid refrigerant from entering the compressor and causing liquid slugging damage during the first start-up after a long period of standby. The aforementioned mode switching mechanism not only ensures the performance of the unit during normal operation, but also makes full use of solar energy to achieve intelligent protection in standby mode, which greatly improves the system's operational safety and energy utilization efficiency.

[0044] In this embodiment, in the cooling mode, the internal passage of the four-way valve 8 is connected to the exhaust port of the compressor 1 and the inlet of the finned heat exchanger 5, and the outlet of the shell-and-tube heat exchanger 3 and the suction port of the compressor 1. The refrigerant flows from the compressor 1 exhaust to the finned heat exchanger 5 for condensation, then through the electronic expansion valve 4 for throttling to the shell-and-tube heat exchanger 3 for evaporation, and finally back to the compressor 1.

[0045] In heating mode, the internal passage of the four-way valve 8 is switched so that the exhaust port of the compressor 1 is connected to the inlet of the shell-and-tube heat exchanger 3, and the outlet of the finned heat exchanger 5 is connected to the suction port of the compressor 1. The refrigerant flows from the exhaust of the compressor 1 to the condensation of the shell-and-tube heat exchanger 3, through the throttling of the electronic expansion valve 4 to the evaporation of the finned heat exchanger 5, and finally back to the compressor 1.

[0046] In the static mode, the internal passage of the four-way valve 8 is switched to the same connected state as in the refrigeration mode, so that the circulating refrigerant driven by the refrigerant pump 7 can flow through the internal cavity of the compressor 1 and use the heat it carries to preheat the compressor 1.

[0047] For example, the photovoltaic panel used in this embodiment is a PVT (Photovoltaic-Temperature Transmission) photovoltaic panel with copper pipe components attached to its back. The PVT photovoltaic panel is a PVT integrated photovoltaic and solar thermal module, which has an internal antifreeze circulation S-shaped channel. This S-shaped channel is tightly fitted to the back of the photovoltaic panel to absorb waste heat generated during photovoltaic power generation and directly absorb solar radiation heat energy, while also cooling the photovoltaic panel and improving photoelectric conversion efficiency. The PVT integrated photovoltaic and solar thermal module has an area of ​​2.58 m², a total power of 1735 W, of which the solar thermal power is 1150 W and the photovoltaic power is 585 W, with a total efficiency of 67.2%, a solar thermal efficiency of 44.6%, and a photovoltaic efficiency of 22.6%. In static mode, the refrigerant is driven by a fluorine pump into the S-shaped flow channel inside the photovoltaic panel, where it exchanges heat with the channel wall, absorbs solar heat collected by the photovoltaic panel, and then heats up and evaporates, thus circulating and heating the liquid refrigerant that migrates and accumulates in the finned heat exchanger. In cooling or heating mode, the S-shaped flow channel can also be used for antifreeze circulation to prevent the photovoltaic panel from freezing and cracking in low-temperature environments. This embodiment, through the integrated PVT design, achieves the synergistic utilization of photovoltaic and photothermal energy, providing clean heat sources for system static start-up while supplying electrical energy, significantly improving overall energy utilization efficiency and system reliability.

[0048] Example 3 This embodiment provides a static start-up control method for a photovoltaic heat pump system, such as... Figure 4 The flowchart shown below illustrates the static start-up control method for a photovoltaic heat pump system, which includes the following steps: S1: Use controller 9 to record the standby time of the photovoltaic heat pump system and read the temperature of the finned heat exchanger, the ambient temperature and the photovoltaic panel temperature; S2: Determine whether the standby time of the photovoltaic heat pump system is less than the first threshold. If the standby time is less than the first threshold, proceed to step S3; otherwise, proceed to step S4. S3: Determine whether the ambient temperature is lower than the preset ambient temperature threshold. If the ambient temperature is lower than the preset temperature threshold, the controller 9 controls the crankshaft heating belt 2 to start and heat the compressor 1. Otherwise, the photovoltaic heat pump system is in normal standby mode, the electronic expansion valve 4 is closed, and the shell-and-tube heat exchanger 3 and the four-way valve 8 are not started. S4: Determine whether the temperature of the finned heat exchanger 5 is lower than the preset finned heat exchanger temperature threshold. If yes, execute step S5; otherwise, controller 9 controls crankshaft heating belt 2 to start and heat compressor 1. S5: Determine whether the temperature of the photovoltaic panel 6 is lower than the temperature of the finned heat exchanger. If so, the controller 9 controls the crankshaft heating belt 2 to start and heat the compressor 1. Otherwise, the controller 9 controls the crankshaft heating belt 2 to start and heat the compressor 1. The refrigerant pump 7 starts, and the four-way valve 8 and the electronic expansion valve 4 open.

[0049] For example, the first threshold for the standby time of the photovoltaic heat pump system is set to 24 hours. The preset ambient temperature threshold is set to -5°C.

[0050] In this embodiment, the controller 9 controls the crankshaft heating belt 2 to start, and the process of heating the compressor 1 is as follows: Step 1: Controller 9 controls the crankshaft heating belt 2 to start, heating compressor 1; Step 2: When the crankshaft heating belt 2 reaches the first preset time, the controller 9 controls the crankshaft heating belt 2 to stop heating; Step 3: When the crankshaft heating belt 2 stops for the second preset time, return to step 1 until the photovoltaic heat pump system receives a start command or meets the conditions for switching to the second standby mode.

[0051] For example, the first preset time is set to 6 minutes. The second preset time is set to 10 minutes.

[0052] In this embodiment, the process of starting the fluorine pump 7 and opening the four-way valve 8 and the electronic expansion valve 4 is as follows: Step 1: Controller 9 controls solenoid valve 10 to open and refrigerant pump 7 to start; Step 2: During the operation of refrigerant pump 7, monitor the temperature difference between the finned heat exchanger temperature T2 and the ambient temperature T1. When the temperature difference exceeds the preset temperature difference threshold, the controller 9 controls the refrigerant pump 7 to stop in advance and the solenoid valve 10 to close; otherwise, proceed to step three. Step 3: After the refrigerant pump 7 has been running for the third preset time, the controller 9 controls the refrigerant pump 7 to stop and the solenoid valve 10 to close. Step 4: When the stop time of the refrigerant pump 7 reaches the fourth preset time, the controller 9 controls the solenoid valve 10 to open and the refrigerant pump 7 to start. Step 5: When the refrigerant pump 7 has been running for the fifth preset time, the controller 9 controls the refrigerant pump 7 to stop and the solenoid valve 10 to close. Step Six: Repeat steps four and five until the photovoltaic heat pump system receives a start command.

[0053] For example, the preset temperature difference threshold is set to 10℃. The third preset time is set to 15 minutes. The fourth preset time is set to 5 minutes. The fifth preset time is set to 30 minutes.

[0054] In this embodiment, the standby time of the photovoltaic heat pump system is obtained in two ways based on the actual state of the system: The first scenario: Unit power-on standby; When the system is continuously powered on but not running, the controller 9 records the continuous standby time of the system in real time through its internal clock, that is, the time interval from the moment of power-on to the current moment, as the standby duration h. In this state, the system always remains powered on, and the controller continuously monitors the standby duration and prepares to execute the corresponding standby protection mode according to the preset logic.

[0055] The second scenario: Initial startup after a power outage and initial standby. When the system restarts after a power outage, controller 9 reads the stored time from before the power outage and compares it with the current time. The difference between the power outage time and the current time is calculated as the standby time h after the power outage restart. In this state, the system accurately obtains the duration of the entire power outage and standby period by remembering the power outage time, avoiding misjudging a short standby state due to the standby time being reset to zero because of a power outage.

[0056] The power outage memory unit is a logic component of the electrical control software. Its storage method is consistent with the recording units that occur during normal unit regulation. For example, if the unit loses power at 12:00, the date and time are recorded. When power is restored next time, the current time, such as 13:00, will be recorded, with the difference being 1 hour. Time recording is not required during the power outage process. By distinguishing between the two standby time acquisition methods mentioned above, the controller 9 can accurately determine the actual standby time of the system. When h < 24h, it is treated as short standby, and the controller 9 controls the crankshaft heating belt 2 to start and heat the compressor 1. When h ≥ 24h, it is treated as long standby, and the refrigerant pump 7 starts when the temperature conditions are met, and the four-way valve 8 and the electronic expansion valve 4 open, ensuring that the system can obtain an appropriate standby protection strategy under various operating conditions.

[0057] The refrigerant pump is continuously activated, causing the refrigerant at the bottom to circulate continuously between the photovoltaic panel and the bottom of the fins. After the circulation cycle is completed, the refrigerant at the bottom of the fins will spontaneously flow and displace due to thermodynamic properties and temperature difference, generating new low-temperature refrigerant at the bottom, which will then be circulated again by the refrigerant pump. This circulation process only needs to circulate the refrigerant in the last path at the bottom of the fins (due to the thermodynamic properties of the refrigerant, it is known that a large amount of refrigerant passing through the photovoltaic panel at once would not be supported by the photovoltaic panel's heating power). The heat exchange of the photovoltaic panel can also meet the heat exchange problem of the refrigerant in a single flow path, and the power consumption of the refrigerant pump will be very low.

[0058] The embodiments described are merely examples to clearly illustrate the present invention and are not intended to limit the implementation of the invention. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all possible implementations. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A photovoltaic heat pump system, characterized by include: Compressor (1), crankshaft heating belt (2), shell and tube heat exchanger (3), electronic expansion valve (4), finned heat exchanger (5), photovoltaic panel (6), fluorine pump (7), four-way valve (8) and controller (9); The exhaust port of the compressor (1) is connected to the first port of the four-way valve (8), and the intake port of the compressor (1) is connected to the second port of the four-way valve (8); a crankshaft heating belt (2) is provided at the bottom of the compressor (1); the third port of the four-way valve (8) is connected to the first port of the shell-and-tube heat exchanger (3), and the fourth port of the four-way valve (8) is connected to the first port of the finned heat exchanger (5); the second port of the shell-and-tube heat exchanger (3) is connected to the first port of the electronic expansion valve (4); the second port of the electronic expansion valve (4) is connected to the second port of the finned heat exchanger (5). The photovoltaic panel (6) and the finned heat exchanger (5) are connected in parallel with a first branch and a second branch; the inlet of the photovoltaic panel (6) is connected to the second port of the finned heat exchanger (5) through the first branch, and a fluorine pump (7) is provided on the first branch; the outlet of the photovoltaic panel (6) is connected to the first port of the finned heat exchanger (5) through the second branch. The crankshaft heating belt (2) and the fluorine pump (7) are respectively connected to the controller (9).

2. A photovoltaic heat pump system according to claim 1, wherein, The first branch is also equipped with a solenoid valve (10); one end of the solenoid valve (10) is connected to the second port of the finned heat exchanger (5); the other end of the solenoid valve (10) is connected to the fluorine pump (7); the solenoid valve (10) and the controller (9) are connected for control.

3. A photovoltaic heat pump system according to claim 1, wherein, The second branch is provided with a one-way valve (11), the inlet of which is connected to the outlet of the photovoltaic panel (6), and the outlet of which is connected to the first interface of the finned heat exchanger (5).

4. The photovoltaic heat pump system of claim 1, wherein, It also includes a gas-liquid separator (12), the inlet of which is connected to the second port of the four-way valve (8); the outlet of which is connected to the suction port of the compressor (1).

5. A photovoltaic heat pump system according to claim 1, wherein, Also includes: A first temperature sensor (13), a second temperature sensor (14), and a third temperature sensor (15); the first temperature sensor (13) is located at the bottom flow path of the finned heat exchanger (5) and is used to detect the temperature at the bottom of the finned heat exchanger; the second temperature sensor (14) is located at the top of the finned heat exchanger (5) and is used to detect the ambient temperature; the third temperature sensor (15) is located on the surface of the photovoltaic panel (6) and is used to detect the surface temperature of the photovoltaic panel; the first temperature sensor (13), the second temperature sensor (14), and the third temperature sensor (15) are electrically connected to the controller (9).

6. A photovoltaic heat pump system according to claim 1, wherein, It also includes a distributor (16), a gas collection pipe (17), a first tee (18), and a second tee (19); The first port of the first tee (18) is connected to the finned heat exchanger (5), the second port of the first tee (18) is connected to the outlet of the distributor (16), and the third port of the first tee (18) is connected to the solenoid valve (10). The inlet of the distributor (16) is connected to the second port of the electronic expansion valve (4); the outlet of the distributor (16) is also connected to the finned heat exchanger (5). The first port of the second three-way valve (19) is connected to the finned heat exchanger (5), the second port of the second three-way valve (19) is connected to the inlet of the gas collecting pipe (17), and the third port of the second three-way valve (19) is connected to the one-way valve (11). The inlet of the gas collecting pipe (17) is also connected to the finned heat exchanger (5); the outlet of the gas collecting pipe (17) is connected to the fourth port of the four-way valve (8).

7. A photovoltaic heat pump system according to claim 1, wherein, The photovoltaic heat pump system has a cooling mode, a heating mode, and a static mode. In the cooling mode and heating mode, the controller (9) controls the solenoid valve (10) to close, the refrigerant pump (7) to stop running, the first branch is disconnected, and the second branch is not connected; In the static mode, the controller (9) controls the solenoid valve (10) to open, the fluorine pump (7) to start, and the second branch to be connected.

8. A method for static start-up control of the photovoltaic heat pump system according to any one of claims 1-7, characterized in that, Includes the following steps: S1: Use the controller (9) to record the standby time of the photovoltaic heat pump system and read the finned heat exchanger temperature, ambient temperature and photovoltaic panel temperature; S2: Determine whether the standby time of the photovoltaic heat pump system is less than the first threshold. If the standby time is less than the first threshold, proceed to step S3; otherwise, proceed to step S4. S3: Determine whether the ambient temperature is less than the preset ambient temperature threshold. If the ambient temperature is less than the preset temperature threshold, the controller (9) controls the crankshaft heating belt (2) to start and heat the compressor (1); otherwise, the photovoltaic heat pump system is in normal standby mode, the electronic expansion valve (4) is closed, and the shell heat exchanger (3) and the four-way valve (8) are not started. S4: Determine whether the finned heat exchanger temperature of the finned heat exchanger (5) is less than the preset finned heat exchanger temperature threshold. If yes, execute step S5; otherwise, the controller (9) controls the crankshaft heating belt (2) to start and heat the compressor (1). S5: Determine whether the temperature of the photovoltaic panel (6) is lower than the temperature of the finned heat exchanger. If so, the controller (9) controls the crankshaft heating belt (2) to start and heat the compressor (1). Otherwise, the controller (9) controls the crankshaft heating belt (2) to start and heat the compressor (1). The fluorine pump (7) starts and the four-way valve (8) and electronic expansion valve (4) open.

9. The method of claim 8, wherein the method further comprises: The controller (9) controls the crankshaft heating belt (2) to start, and the process of heating the compressor (1) is as follows: Step 1: The controller (9) controls the crankshaft heating belt (2) to start, heating the compressor (1); Step 2: When the crankshaft heating belt (2) reaches the first preset time, the controller (9) controls the crankshaft heating belt (2) to stop heating; Step 3: When the crankshaft heating belt (2) stops for the second preset time, return to step 1 until the photovoltaic heat pump system receives the start command.

10. The method of claim 8, wherein the method further comprises: The process of starting the fluorine pump (7) and opening the four-way valve (8) and electronic expansion valve (4) is as follows: Step 1: The controller (9) controls the four-way valve (8), electronic expansion valve (4) and solenoid valve (10) to open, and the fluorine pump (7) to start; Step two: during the operation of the fluorine pump (7), the temperature difference between the fin heat exchanger temperature T2 and the ambient temperature T1 is detected When the temperature difference is greater than the preset temperature difference threshold, the controller (9) controls the fluorine pump (7) to stop in advance and the electromagnetic valve (10) to close; otherwise, step three is performed. Step 3: After the fluorine pump (7) has been running for the third preset time, the controller (9) controls the fluorine pump (7) to stop and the solenoid valve (10) to close. Step 4: When the stop time of the fluorine pump (7) reaches the fourth preset time, the controller (9) controls the solenoid valve (10) to open and the fluorine pump (7) to start. Step 5: When the fluorine pump (7) runs for the fifth preset time, the controller (9) controls the fluorine pump (7) to stop and the solenoid valve (10) to close. Step Six: Repeat steps four and five until the photovoltaic heat pump system receives a start command.

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