Three-loop PVT heat pump water heating system based on pump-supply

Abstract

This invention provides a three-cycle PVT heat pump water heating system based on pump-supply, comprising a compressor, condenser, expansion valve, PVT components, refrigerant pump, first shut-off valve, second shut-off valve, third shut-off valve, low-pressure circulation tank, first one-way valve, second one-way valve, receiver, and inverter. The compressor exhaust is connected to the first one-way valve, third shut-off valve, and one end of the condenser via the second one-way valve. The other end of the condenser is connected to the first shut-off valve and expansion valve via the receiver. The first outlet of the low-pressure circulation tank is connected to the compressor intake port, and the second outlet is connected to the inlet of the first one-way valve. This PVT heat pump water heating system can operate in three cycles: refrigerant cooling pump supply, refrigerant refrigeration pump supply, and refrigerant siphon pump supply. The large number of PVT components provides uniform refrigerant supply, the refrigerant pump forces multiple refrigerant supplies to the PVT components, the PVT component temperature is low and uniform, the compressor exhaust temperature is low, the heat pump heating coefficient is high, and the comprehensive utilization rate of solar energy is high.

Description

Technical Field

[0001] This invention relates to the field of solar heat pump technology, and more specifically, to a PVT heat pump hot water system based on pump-supply that can achieve three types of cycles. Background Technology

[0002] Internationally, the technology for the integrated utilization of solar photovoltaic and solar thermal energy is called PVT (Photovoltaic-thermal). PVT technology can generate both electricity and heat, exhibiting high overall solar energy utilization efficiency. Combining PVT technology with heat pump technology creates a PVT heat pump. In a PVT heat pump, the photovoltaic cells within the PVT modules operate under low-temperature conditions with refrigerant evaporation, resulting in high power generation efficiency. Simultaneously, because the heat pump cycle uses solar-irradiated heat collection modules as the evaporative heat source, the coefficient of performance (COP) is significantly improved. Therefore, PVT heat pumps have great development and application potential.

[0003] Existing PVT heat pump water heating systems use a direct refrigerant expansion method for refrigerant supply. The refrigerant gas-liquid mixture from the expansion valve enters from one end of the PVT module's heat exchange tubes. The liquid portion evaporates, absorbing heat from the photovoltaic cells and turning into gas. Upon reaching the other end of the heat exchange tubes, it completely vaporizes and is drawn into the compressor. This refrigerant supply method in PVT heat pump water heating systems may lead to the following problems:

[0004] First, the PVT evaporator has a low heat exchange rate. The refrigerant entering the PVT module is a gas-liquid two-phase mixture. The gas part will form a heat exchange thermal resistance in the heat exchange tube. The small liquid part has low wettability in the tube. The liquid supply method is single liquid supply driven by the compressor, and the refrigerant flow rate is low. These factors limit the overall heat exchange efficiency of the PVT module.

[0005] 2. Not applicable to medium and large-sized PVT heat pump water heating systems. Medium and large-sized PVT heat pump water heating systems contain multiple PVT arrays, and each array contains multiple PVT components. The total number of PVT components is large. The refrigerant flowing from the expansion valve into each PVT array is a gas-liquid two-phase flow, which is prone to uneven liquid distribution. This uneven liquid supply between PVT components is particularly noticeable for PVT components with strong changes in heat load throughout the day. It will cause uneven temperature distribution in the PVT array, and the PVT array cannot be fully utilized. It will also lead to differences in photovoltaic current and voltage within the PVT components.

[0006] 3. The compressor has a high suction superheat. The distance between the compressor suction port and the refrigerant outlet of the PVT component is far. The suction pipeline between the two is long. The pipeline exchanges more heat with the outside, resulting in more harmful superheat. The compressor volumetric cooling capacity is reduced, the compressor performance is smaller, and the compressor discharge temperature is higher.

[0007] IV. Heating interruption under high temperature and high light intensity conditions: In hot summer with strong sunlight, the refrigerant pressure inside the PVT module is high. Under high evaporation pressure conditions, the compressor cannot start due to pressure protection and can no longer cool the high temperature photovoltaic cells, resulting in reduced photovoltaic cell power generation efficiency. At the same time, due to the suspension of refrigerant circulation, the heat pump condenser is interrupted. Summary of the Invention

[0008] The purpose of this invention is to address the technical deficiencies in the existing technology by providing a PVT heat pump water heating system that can realize refrigerant cooling pump liquid supply circulation, refrigerant refrigeration pump liquid supply circulation, and refrigerant siphon pump liquid supply circulation.

[0009] The technical solution of this invention is:

[0010] A schematic diagram of a three-circulation PVT heat pump water heating system based on pump-supply is shown below. Figure 1 As shown, the system includes a compressor, a condenser, an expansion valve, a PVT assembly, a refrigerant pump, a first shut-off valve, a second shut-off valve, a third shut-off valve, a low-pressure circulation tank, a first one-way valve, a second one-way valve, a receiver, and an inverter. The compressor discharge port is connected to the refrigerant inlet of the condenser, one end of the third shut-off valve, and the outlet of the first one-way valve via the second one-way valve. The refrigerant outlet of the condenser is connected to the inlet of the receiver. One end of the expansion valve connected in parallel with the first shut-off valve is connected to the outlet of the receiver, and the other end is connected to the inlet of the low-pressure circulation tank. The outlet of the low-pressure circulation tank is connected to the suction port of the refrigerant pump. The outlet of the refrigerant pump is connected to the inlet of the heat exchange tube of the PVT assembly. The outlet of the heat exchange tube of the PVT assembly is connected to one end of the second shut-off valve and the other end of the third shut-off valve. The other end of the second shut-off valve is connected to the return port of the low-pressure circulation tank. The first outlet of the low-pressure circulation tank is connected to the suction port of the compressor, and the second outlet of the low-pressure circulation tank is connected to the inlet of the first one-way valve. The photovoltaic cells in the PVT module are connected to the inverter.

[0011] The present invention relates to a three-cycle PVT heat pump water heating system based on pump-supply, which can be divided into three types of circulation based on ambient temperature and light intensity: refrigerant cooling pump-supply circulation, refrigerant radiant cooling pump-supply circulation, and refrigerant siphon pump-supply circulation.

[0012] When the ambient temperature is low and the light intensity is low, the PVT heat pump water heating system of this invention operates by circulating refrigerant-cooled pumps, as shown in the operating principle diagram. Figure 2As shown, the first and third shut-off valves are closed, the second shut-off valve is open, the opening degree of the expansion valve is controlled according to the liquid level of the low-pressure circulating tank, the compressor is started, the refrigerant pump is started, and the photovoltaic cells in the PVT module generate electricity under sunlight, which is then converted into electricity usable by the inverter.

[0013] When the ambient temperature is high and the light intensity is strong, the PVT component and the refrigerant in the low-pressure circulation tank are under high pressure. The compressor cannot start due to pressure protection. The PVT heat pump water heating system of this invention operates by circulating refrigerant via a refrigerant siphon pump. The operating principle diagram is shown below. Figure 3 As shown, the first and second shut-off valves are open, the third shut-off valve is closed, the compressor stops, the refrigerant pump starts, and the photovoltaic cells in the PVT module generate electricity under sunlight, which is then converted into usable electricity by the inverter.

[0014] When the ambient temperature and light intensity are moderate, the PVT component and the refrigerant in the low-pressure circulation tank are under high pressure. The compressor cannot start due to pressure protection. The PVT heat pump water heating system of this invention operates by circulating refrigerant via a refrigerant-cooled pump. The operating principle diagram is shown below. Figure 4 As shown, the first and third shut-off valves are open, the second shut-off valve is closed, the compressor stops, the refrigerant pump starts, and the photovoltaic cells in the PVT module generate electricity under sunlight, which is then converted into usable electricity by the inverter.

[0015] In the three-circulation PVT heat pump water heating system based on pump-supply, the condenser is installed at a vertical height greater than the highest position of the liquid storage tank, and the liquid storage tank is installed at a vertical height greater than the highest position of the low-pressure circulation tank.

[0016] The PVT assembly is any one of the following: flat box type, tube sheet type, blown plate type, and flat plate type.

[0017] The compressor is any one of a scroll compressor, rotary compressor, screw compressor, or piston compressor.

[0018] The condenser is a plate heat exchanger, a shell-and-tube heat exchanger, a shell-and-tube heat exchanger, or a plate-and-shell heat exchanger.

[0019] The expansion valve is an electronic expansion valve, a thermal expansion valve, a capillary tube, or an orifice plate throttling device.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] 1. In this invention, the refrigerant entering the PVT module in a pump-supply three-cycle PVT heat pump water heating system is a pure liquid, while the gas inside the pipe is generated by the evaporation of some of the liquid. The liquid volume is relatively large, resulting in good wetting inside the pipe. Furthermore, the refrigerant supply is pump-driven, resulting in a high refrigerant flow rate within the pipe. The high wettability and high flow rate on the refrigerant side increase the heat transfer coefficient. The temperature difference between the refrigerant and the photovoltaic cells is smaller, leading to higher overall solar energy utilization efficiency of the PVT module.

[0022] 2. Regardless of whether the three-cycle PVT heat pump water heating system based on pump supply operates in the form of refrigerant-cooled pump supply cycle, refrigerant-cooled pump supply cycle, or refrigerant siphon pump supply cycle, the PVT components are supplied with pure liquid at a uniform temperature. This makes it more suitable for medium and large-scale PVT heat pump water heating systems with a large number of PVT components. The liquid distribution between PVT components is more uniform, the overall temperature distribution of PVT components is more uniform, the voltage and current differences within the photovoltaic components are smaller, and the power generation efficiency is higher.

[0023] 3. In the three-cycle PVT heat pump water heating system based on pump-supply of the present invention, the compressor can be installed near the low-pressure circulation tank. The suction pipe connecting the compressor and the low-pressure circulation tank is shorter, the friction resistance of the refrigerant flowing in the suction pipe is smaller, the harmful superheat of the suction pipe is close to zero, the compressor suction superheat is smaller, the exhaust temperature is lower, the compressor volumetric cooling capacity is larger, and the performance is better. In addition, the low-pressure circulation tank can be installed on the lower side of the PVT component, making installation more convenient.

[0024] 4. The three-cycle PVT heat pump water heating system based on pump-supply operates with refrigerant siphon pump-supply under conditions of high ambient temperature and high light intensity. It achieves uninterrupted heating of the condenser without starting the compressor, and can also achieve forced high-speed liquid supply to the PVT module to continuously cool the photovoltaic cells. The PVT module has high power generation efficiency.

[0025] 5. The three-cycle PVT heat pump water heating system based on pump-supply can be divided into three types of circulation according to ambient temperature and light intensity: refrigerant cooling pump-supply circulation, refrigerant radiant cooling pump-supply circulation, and refrigerant siphon pump-supply circulation. The multiple circulation switching is flexible and the equipment utilization rate is high. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the three-circulation PVT heat pump water heating system based on pump-supply according to the present invention;

[0027] Figure 2 This is a schematic diagram of the operating principle of the three-cycle PVT heat pump hot water system based on pump supply of the present invention, which uses a refrigerant-cooled pump to supply liquid in a circulating cycle.

[0028] Figure 3This is a schematic diagram of the operating principle of the three-circulation PVT heat pump hot water system based on pump-supply of refrigerant using a refrigerant siphon pump.

[0029] Figure 4 This is a schematic diagram of the operating principle of the three-cycle PVT heat pump hot water system based on pump supply of the present invention, which uses a refrigerant-cooled pump for liquid supply and circulation.

[0030] Figure 5 This is a schematic diagram of the low-pressure circulation tank interface in the three-circulation PVT heat pump water heating system based on pump-supply according to the present invention.

[0031] In the diagram: 1. Compressor; 2. Condenser; 3. Expansion valve; 4. PVT assembly; 5. Refrigerant pump; 6-1. First shut-off valve; 6-2. Second shut-off valve; 6-3. Third shut-off valve; 7. Low-pressure circulation tank; 7-1. Liquid return port; 7-2. First gas outlet; 7-3. First gas outlet; 7-4. Liquid outlet; 7-5. Liquid inlet; 8-1. First check valve; 8-2. Second check valve; 9. Receiver; 10. Inverter. Detailed Implementation

[0032] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0033] The schematic diagram of the three-circulation PVT heat pump water heating system based on pump-supply in this invention is shown below. Figure 1 As shown, the system includes a compressor 1, a condenser 2, an expansion valve 3, a PVT assembly 4, a refrigerant pump 5, a first shut-off valve 6-1, a second shut-off valve 6-2, a third shut-off valve 6-3, a low-pressure circulation tank 7, a first one-way valve 8-1, a second one-way valve 8-2, a liquid receiver 9, and an inverter 10. The discharge port of the compressor 1 is connected to the refrigerant inlet of the condenser 2, a section of the third shut-off valve 6-3, and the outlet of the first one-way valve 8-1 via the second one-way valve 8-2. The refrigerant outlet of the condenser 2 is connected to the inlet of the liquid receiver 9. One end of the expansion valve 3 connected in parallel with the first shut-off valve 6-1 is connected to... The outlet of the liquid receiver 9 is connected to the inlet of the low-pressure circulation tank 7; the outlet of the low-pressure circulation tank 7 is connected to the suction port of the refrigerant pump 5; the outlet of the refrigerant pump 5 is connected to the inlet of the heat exchange tube of the PVT assembly 4; the outlet of the heat exchange tube of the PVT assembly 4 is connected to one end of the second shut-off valve 6-2 and the other end of the third shut-off valve 6-3; the other end of the second shut-off valve 6-2 is connected to the return port of the low-pressure circulation tank 7; the first air outlet of the low-pressure circulation tank 7 is connected to the suction port of the compressor 1; and the second air outlet of the low-pressure circulation tank 7 is connected to the inlet of the first one-way valve 8-1. The photovoltaic cells in the PVT assembly 4 are connected to the inverter 10.

[0034] The present invention relates to a three-cycle PVT heat pump water heating system based on pump-supply, which can be divided into three types of circulation based on ambient temperature and light intensity: refrigerant cooling pump-supply circulation, refrigerant radiant cooling pump-supply circulation, and refrigerant siphon pump-supply circulation.

[0035] When the ambient temperature is low and the light intensity is low, the PVT heat pump water heating system of this invention operates by circulating refrigerant-cooled pumps, as shown in the operating principle diagram. Figure 2 As shown, the first shut-off valve 6-1 and the third shut-off valve 6-3 are closed, the second shut-off valve 6-2 is open, and the opening degree of the expansion valve 3 is controlled according to the liquid level of the low-pressure circulation tank 7, the start of the compressor 1, and the start of the refrigerant pump 5. Refrigerant thermodynamic flow: The compressor 1 draws in low-pressure refrigerant gas through the first outlet of the low-pressure circulation tank 7. After compression and pressure increase, it becomes high-pressure superheated gas and is discharged into the condenser 2 through the second shut-off valve 6-2. The superheated gas exchanges heat with water on the other side in the condenser 2 and is condensed into high-pressure liquid refrigerant, flowing into the liquid receiver 9. The liquid refrigerant flowing out of the liquid receiver 9 expands and depressurizes through the expansion valve 3, becoming a saturated low-pressure gas-liquid two-phase mixture. The mixture enters the low-pressure circulation tank 7 for gas-liquid separation, and the separated saturated liquid settles in the low-pressure circulation tank. At the bottom of the PVT module 4, the refrigerant is pumped by the refrigerant pump 5 and then transported to the PVT module 4. Part of the liquid refrigerant absorbs heat from the photovoltaic cells within the PVT module 4 and evaporates into saturated gas. This saturated gas, along with the unevaporated liquid, forms a two-phase gas-liquid mixture that returns to the low-pressure circulation tank 7 via the second shut-off valve 6-2. The unevaporated saturated liquid remains at the bottom of the low-pressure circulation tank 7 for the next round of liquid supply circulation. The evaporated saturated gas, along with the gas from the two-phase mixture from the expansion valve 3, is drawn into the compressor 1, completing the refrigerant cycle. The photovoltaic cells in the PVT module 4 generate electricity under sunlight, which is then converted into usable electricity by the inverter 10.

[0036] When the ambient temperature is high and the light intensity is strong, the refrigerant in the PVT component 4 and the low-pressure circulation tank 7 is under high pressure. The compressor 1 cannot start due to pressure protection. The PVT heat pump water heating system of this invention operates by circulating refrigerant via a refrigerant siphon pump. The operating principle diagram is shown below. Figure 3As shown, the first shut-off valve 6-1 and the second shut-off valve 6-2 are open, and the third shut-off valve 6-3 is closed. The compressor 1 stops, and the refrigerant pump 5 starts. Refrigerant thermodynamic flow: The liquid at the bottom of the low-pressure circulation tank 7 is transported to the PVT component 4 by the refrigerant pump 5. Part of the liquid refrigerant absorbs heat from the photovoltaic cells in the PVT component 4 and evaporates into saturated gas. This saturated gas and the unevaporated liquid form a two-phase gas-liquid fluid that returns to the low-pressure circulation tank 7 via the second shut-off valve 6-2. The unevaporated saturated liquid settles at the bottom of the low-pressure circulation tank 7 for the next liquid supply cycle. The evaporated saturated gas, according to the siphon principle, enters the condenser 2 through the first one-way valve 8-1. In the condenser 2, it exchanges heat with water on the other side and is condensed into liquid refrigerant, which flows into the liquid receiver 9 under gravity. The liquid in the liquid receiver 9 then flows out from the outlet under gravity and returns to the low-pressure circulation tank 7 via the first shut-off valve 6-1, completing the refrigerant cycle. The photovoltaic cells in the PVT module 4 generate electricity under sunlight, which is then converted into usable electricity by the inverter 10.

[0037] When the ambient temperature and light intensity are moderate, the refrigerant in the PVT component 4 and the low-pressure circulation tank 7 is under high pressure. The compressor 1 cannot start due to pressure protection. The PVT heat pump water heating system of this invention operates by circulating refrigerant via a refrigerant-cooled pump. The operating principle diagram is shown below. Figure 4 As shown, the first shut-off valve 6-1 and the third shut-off valve 6-3 are open, the second shut-off valve 6-2 is closed, the compressor 1 stops, and the refrigerant pump 5 starts. Refrigerant thermodynamic flow: The liquid at the bottom of the low-pressure circulation tank 7 is transported to the PVT assembly 4 by the refrigerant pump 5. Part of the liquid refrigerant absorbs heat from the photovoltaic cells in the PVT assembly 4 and evaporates into saturated gas. This saturated gas and the unevaporated liquid form a two-phase fluid, which is transported to the condenser 2 via the third shut-off valve 6-3. The gas in the two-phase fluid exchanges heat with water on the other side in the condenser 2 and is condensed into liquid refrigerant, flowing into the liquid receiver 9. The liquid refrigerant flowing out of the liquid receiver 9 enters the low-pressure circulation tank 7 via the first shut-off valve 6-1. The liquid in the low-pressure circulation tank 7 is transported back to the PVT assembly 4 for heat exchange by the refrigerant pump 5, completing the refrigerant cycle. The photovoltaic cells in the PVT assembly 4 generate electricity under sunlight, which is then converted into usable electricity by the inverter 10.

[0038] In the three-circulation PVT heat pump water heating system based on pump-supply of the present invention, the vertical height of the condenser 2 is greater than the highest position of the liquid storage tank 9, and the vertical height of the liquid storage tank 9 is greater than the highest position of the low-pressure circulation tank 7.

[0039] The above description is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A three-circulation PVT heat pump water heating system based on pump-supply, characterized in that, The refrigerant pump circulating and cooling PVT heat pump water heater includes a compressor, condenser, expansion valve, PVT assembly, refrigerant pump, first shut-off valve, second shut-off valve, third shut-off valve, low-pressure circulation tank, first check valve, second check valve, receiver, and inverter. The compressor discharge port is connected to the condenser refrigerant inlet, one end of the third shut-off valve, and the outlet of the first one-way valve via the second check valve. The condenser refrigerant outlet is connected to the liquid receiver inlet. One end of the expansion valve connected in parallel with the first shut-off valve is connected to the liquid receiver outlet, and the other end is connected to the low-pressure circulation tank inlet. The low-pressure circulation tank outlet is connected to the refrigerant pump suction inlet, and the refrigerant pump outlet is connected to the PVT module heat exchange tube inlet. The PVT module heat exchange tube outlet is connected to one end of the second shut-off valve and the other end of the third shut-off valve. The other end of the second shut-off valve is connected to the low-pressure circulation tank return port. The low-pressure circulation tank first outlet is connected to the compressor suction inlet, and the low-pressure circulation tank second outlet is connected to the first one-way valve inlet. The photovoltaic cells in the PVT module are connected to the inverter.

2. The three-circulation PVT heat pump water heating system based on pump-supply as described in claim 1, characterized in that, When the ambient temperature is low and the light intensity is low, the PVT heat pump water heater operates in a refrigerant-cooled pump circulation mode; the first and third shut-off valves are closed, the second shut-off valve is open, the opening degree of the expansion valve is controlled according to the liquid level in the low-pressure circulation tank, the compressor starts, the refrigerant pump starts, and the photovoltaic cells in the PVT module generate electricity under sunlight, which is then converted into electricity usable by the user through the inverter.

3. The three-circulation PVT heat pump water heating system based on pump-supply as described in claim 1, characterized in that, When the ambient temperature is high and the light intensity is strong, the refrigerant in the PVT module and the low-pressure circulation tank is under high pressure. The compressor cannot start due to pressure protection. The PVT heat pump water heater operates in refrigerant siphon circulation mode. The first and second shut-off valves open, the third shut-off valve closes, the compressor stops, the refrigerant pump starts, and the photovoltaic cells in the PVT module generate electricity under sunlight. The electricity is then converted into usable electricity by the inverter.

4. The three-circulation PVT heat pump water heating system based on pump-supply as described in claim 1, characterized in that, When the ambient temperature and light intensity are moderate, the refrigerant in the PVT module and the low-pressure circulation tank is under high pressure. The compressor cannot start due to pressure protection. The PVT heat pump water heater operates in refrigerant-cooled pump circulation mode. The first and third shut-off valves are open, the second shut-off valve is closed, the compressor stops, the refrigerant pump starts, and the photovoltaic cells in the PVT module generate electricity under sunlight, which is then converted into usable electricity by the inverter.

5. The three-circulation PVT heat pump water heating system based on pump-supply as described in claim 1, characterized in that, The PVT assembly is any one of the following: flat box type, tube sheet type, blown plate type, and flat plate type.

6. The three-circulation PVT heat pump water heating system based on pump-supply as described in claim 1, characterized in that, The compressor is any one of a scroll compressor, rotary compressor, screw compressor, or piston compressor.

7. The three-circulation PVT heat pump water heating system based on pump-supply as described in claim 1, characterized in that, The condenser is a plate heat exchanger, a shell-and-tube heat exchanger, a shell-and-tube heat exchanger, or a plate-and-shell heat exchanger.

8. The three-circulation PVT heat pump water heating system based on pump-supply as described in claim 1, characterized in that, The expansion valve is an electronic expansion valve, a thermostatic expansion valve, a capillary tube, or an orifice plate throttling device.

9. The three-circulation PVT heat pump water heating system based on pump-supply as described in claim 1, characterized in that, In the three-circulation PVT heat pump water heating system based on pump-supply, the condenser is installed at a vertical height greater than the highest point of the liquid receiver, and the liquid receiver is installed at a vertical height greater than the highest point of the low-pressure circulation tank.

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