A photovoltaic photo-thermal and heat pump coupled combined cooling, heating and power system and a control method thereof

Abstract

The present application belongs to the technical field of efficient utilization of renewable energy, and particularly relates to a combined cooling, heating and power system coupled with photovoltaic and heat pump and a control method thereof. A PV / T light and heat cooling water system is coupled with a low-temperature stage heat pump system through a low-temperature stage evaporator or coupled with a CO2 heat pump system through a CO2 evaporator, the low-temperature stage heat pump system is coupled with a high-temperature stage heat pump system through a condenser evaporator, the PV / T light and heat cooling water system is connected with cold users, and the CO2 heat pump system and the high-temperature stage heat pump system are connected with cold water / hot water / medium-temperature water / high-temperature water users; working water heated in the PV / T light and heat cooling water system is used as a heat source of the CO2 heat pump or the low-temperature stage heat pump and the CO2 heat pump to supply cold or heat to the users. The present application can realize stable and efficient operation of a PV / T photovoltaic system and efficient utilization of light and heat, and through time period independent operation design of a power generation and cold and heat supply system, influences of seasonal fluctuation and daily fluctuation on the system are reduced, and multi-energy combined supply of cold, heat and power is realized.

Description

Technical Field

[0001] This invention belongs to the field of high-efficiency utilization technology of renewable energy, specifically relating to a combined cooling, heating and power system coupled with photovoltaic thermal and heat pump and its control method. Background Technology

[0002] A photovoltaic / thermal system (PV / T system) is a composite system that combines photovoltaic (PV) power generation and solar thermal (ST) collection technologies. It aims to simultaneously extract electricity and heat from the same collector plate. The cooling fluid (water or air) in the PV / T system carries away the heat from the photovoltaic modules, keeping them at a low and efficient operating temperature, thus effectively improving power generation efficiency.

[0003] In PV / T systems, the proportion of solar energy converted into heat is far higher than that of electricity. To further improve the overall efficiency of photovoltaic and solar thermal systems, stable and efficient utilization of solar thermal energy is necessary. Existing technologies generally achieve solar thermal utilization by directly utilizing the heated cooling fluid or by using a heat pump to raise the temperature. However, direct heat utilization generally requires high-quality thermal energy, which makes it difficult to effectively reduce the temperature of photovoltaic modules and will sacrifice power generation efficiency to some extent. Utilizing solar thermal energy through a heat pump can maximize the efficiency of photovoltaic and solar thermal energy utilization, representing an improvement solution. However, in PV / T systems, the diurnal variation in solar radiation intensity affects both the photovoltaic system and the operational stability of the solar thermal system. This contradicts the fact that the operation of the solar thermal system is primarily driven by user needs. PV / T systems urgently need to achieve efficient synergy between solar thermal energy storage and energy consumption. Furthermore, in most regions, seasonal fluctuations cause cooling water temperature fluctuations. Summer cooling water temperatures can generally reach 40-60℃, while winter temperatures are usually below 40℃. This can easily cause the circulating working fluid in the heat pump to deviate from its suitable operating temperature range, affecting the efficiency of solar thermal energy utilization and adversely impacting the operational stability of the photovoltaic system.

[0004] Therefore, it is essential to further improve the existing PV / T and heat pump combined system to achieve stable and efficient operation of the PV / T system photovoltaic system and efficient utilization of solar thermal energy, while minimizing the impact of seasonal and diurnal fluctuations on the system, and taking into account user needs to achieve synergy between solar energy, thermal energy and energy consumption. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a combined cooling, heating and power system that couples photovoltaic thermal energy with a heat pump.

[0006] The present invention adopts the following technical solution: A combined cooling, heating and power system coupling photovoltaic (PV) thermal power and heat pump includes a PV / T solar thermal cooling water system, a CO2 heat pump system, a low-temperature heat pump system, and a high-temperature heat pump system. The PV / T solar thermal cooling water system includes a cold water tank, a circulating pump, a PV / T plate, and a hot water tank connected in sequence; the CO2 heat pump system includes a CO2 evaporator, a CO2 compressor, a CO2 three-way valve, a primary air cooler, a secondary air cooler, and a CO2 expansion valve connected in sequence; the low-temperature heat pump system includes a low-temperature evaporator, a low-temperature compressor, a condenser-evaporator, and a low-temperature expansion valve connected in sequence. The outlet of the hot water tank is connected to a circulating water three-way valve. The second circulating water outlet of the circulating water three-way valve is connected to a CO2 evaporator, and the first circulating water outlet is connected to the CO2 evaporator via the low-temperature stage evaporator. The low-temperature stage heat pump system is coupled to the high-temperature stage heat pump system through the condenser-evaporator. The high-temperature stage heat pump system includes an inlet three-way valve, a high-temperature stage compressor, a condenser, a high-temperature stage expansion valve, and an outlet three-way valve that are sequentially connected from the condenser-evaporator. An air-cooled evaporator is also provided between the bypass inlet of the inlet three-way valve and the bypass outlet of the outlet three-way valve. The hot-side inlet of the air-cooled evaporator is connected to the bypass CO2 outlet of the CO2 three-way valve, and the hot-side outlet of the air-cooled evaporator is connected to the hot-side inlet of the secondary air-cooler.

[0007] Preferably, in the high-temperature heat pump system, the condenser includes a primary condenser and a secondary condenser connected in series along the working fluid flow direction. The cold-side inlet of the secondary condenser is connected to the first user's cold water end, and the cold-side outlet of the secondary condenser is connected to the cold-side inlet of the primary condenser and the first user's medium-temperature water end respectively through a medium-temperature water three-way valve. The cold-side outlet of the primary condenser is connected to the user's high-temperature water end.

[0008] Preferably, in the CO2 heat pump system, the cold-side inlet of the first-stage air cooler is connected to the cold water end of the second user, the cold-side outlet of the first-stage air cooler is connected to the hot water end of the second user, the cold-side inlet of the second-stage air cooler is connected to the cold water end of the third user, and the cold-side outlet of the first-stage air cooler is connected to the hot water end of the third user.

[0009] Preferably, a refrigeration heat exchanger is also provided between the CO2 evaporator and the cold water tank. After the circulating water is cooled to chilled water by the hot side of the CO2 evaporator, it enters the refrigeration heat exchanger to supply cooling to the user and heats up before flowing into the cold water tank.

[0010] Preferably, the PV / T board is also connected to a battery for storing electrical energy.

[0011] The present invention further provides a control method for a photovoltaic-thermal-heat-power (PV / T) cogeneration system coupled with a heat pump, as described above. When the PV / T panel in the solar thermal cooling water system is activated by solar thermal energy, the energy storage mode is executed, and simultaneously, the real-time temperature T of the PV / T panel is acquired. p When T p The starting temperature T of the solar thermal cooling water system is greater than the set value. p,sWhen the PV / T plate starts the circulating water cooling mode, the circulating water cooling operation time within the 24-hour operation cycle is recorded as t1; Includes the following steps: S1. Within a 24-hour operating cycle, obtain the total amount of working fluid m1 transferred from the cold water tank to the hot water tank in the circulating water cooling mode of the solar thermal cooling water system, which is the product of the circulating water cooling operating time t1 and the average circulating water flow rate q1; control the amount of working fluid m2 transferred from the hot water tank to the cold water tank within the 24-hour operating cycle to be equal to m1, where m2 is the product of the combined cooling and heating time t2 within the 24-hour operating cycle and the average flow rate q2 of the working fluid transferred from the hot water tank to the cold water tank, and the combined cooling and heating time t2 is the operating time of the CO2 heat pump system B; S2. Obtain the water temperature T in the hot water tank. h When T h When the temperature is >35℃, the first circulating water outlet of the circulating water three-way valve is opened, and the second circulating water outlet of the circulating water three-way valve and the bypass CO2 outlet of the CO2 three-way valve are closed. The hot water in the hot water tank flows into the hot side of the low-temperature stage evaporator, cools down, and then enters the hot side of the CO2 evaporator for further cooling. Finally, after passing through the refrigeration heat exchanger to supply cooling capacity to the cold user, it enters the cold water tank. The working fluid of the high-temperature stage heat pump system absorbs heat through the condenser-evaporator, and in the condenser, it heats the water from the cold water end of the first user to medium-temperature water and delivers it to the medium-temperature water end of the first user and / or heats it to high-temperature water and delivers it to the high-temperature water end of the user. The CO2 working fluid of the CO2 heat pump system absorbs heat through the CO2 evaporator, and in the first-stage air cooler, it heats the cold water from the cold water end of the second user and delivers it to the hot water end of the second user. When T h When the temperature is ≤35℃, open the second circulating water outlet of the circulating water three-way valve and the bypass CO2 outlet of the CO2 three-way valve, and close the first circulating water outlet of the circulating water three-way valve. The hot water in the hot water tank flows into the hot side of the CO2 evaporator, and after cooling, it enters the refrigeration heat exchanger to provide cooling capacity to the user, and then enters the cold water tank. After the CO2 working fluid of the CO2 heat pump system is heated by the CO2 evaporator and the CO2 compressor, part of it heats the cold water from the second user's cold water end in the first-stage air cooler and delivers it to the second user's hot water end, and the other part enters the hot side of the air-cooled evaporator to release heat. The working fluid of the high-temperature stage heat pump system absorbs heat through the air-cooled evaporator and heats the water from the first user's cold water end to medium-temperature water in the condenser and delivers it to the first user's medium-temperature water end and / or heats it to high-temperature water and delivers it to the user's high-temperature water end.

[0012] Preferably, the real-time temperature T of the PV / T plate is controlled by controlling the circulating water flow rate. p It is within the efficient operating temperature range required for power generation; specifically, monitoring... T p The change value within a set time period, when Tp When the temperature rises beyond the maximum value of the set range within the set time, the circulating pump speed is adjusted to increase the circulating water flow rate by 10%; when T p If the temperature drops beyond the maximum value of the set range within the set time, adjust the circulating pump speed to reduce the circulating water flow rate by 10%, until... T p The change value stabilizes within the set range within a set time period; the set time interval is 5 min, and the set range is 0~5℃.

[0013] Preferably, the initial circulating water flow rate q water According to the rated heat collection power P of the PV / T panel heat The calculation is performed using the following formula: q water =P heat / (c water ·ΔT water ); In the formula, q water The unit is kg / s; P heat The unit is kW; c water ΔT is the specific heat capacity of the circulating cooling water, expressed in kJ / (kg·℃); water This is the theoretical temperature rise of the circulating cooling water, in °C. The values ​​are set as follows: 23°C when the daily maximum temperature is <25°C, and 33°C when the daily maximum temperature is ≥25°C.

[0014] Preferably, the high-efficiency operating temperature required for power generation is ≤50℃; the start-up temperature T of the photothermal cooling water system is <25℃. p,s The start-up temperature T of the thermal cooling water system is set at 40℃, with a daily maximum temperature ≥25℃. p,s Set to 50℃.

[0015] Preferably, the supply of medium-temperature water to the first user and the supply of high-temperature water to the user are adjusted by adjusting the flow rate ratio of the medium-temperature water three-way valve.

[0016] The beneficial effects of this invention are as follows: 1) By coupling the photovoltaic thermal system with a multi-stage heat pump, the system is designed for multiple operating conditions considering seasonal characteristics and an efficient system control method is proposed. This ensures that the photovoltaic modules are in the high-efficiency operating temperature range while making full use of solar thermal energy, thus significantly improving the overall utilization efficiency of solar energy. At the same time, the solar thermal energy is stored in a hot water tank through circulating cooling water, which facilitates independent operation of power generation and combined cooling and heating within a 24-hour operating cycle. Energy can be supplied in time periods according to user needs, and the impact of daily fluctuations in solar radiation on the stability of solar thermal utilization is effectively reduced.

[0017] 2) The circulating cooling water that has absorbed solar heat through the PV / T panels is cooled by a heat pump. While supplying domestic hot water and high-temperature water / steam, it also generates low-temperature chilled water to supply cooling to users. This system realizes the combined cooling, heating and power supply of the photovoltaic thermal system to meet various energy needs.

[0018] 3) It makes full use of the characteristic that the evaporation temperature of the environmentally friendly working fluid CO2 can be much lower than the ambient temperature, ensuring that the circulating water can achieve stable and deep cooling after flowing through the heat pump system. This effectively prevents the photovoltaic modules from overheating due to the inability to remove heat in time when using a normal temperature working fluid, and ensures the safe and reliable operation of the photovoltaic system.

[0019] 4) The temperature of the circulating cooling water after absorbing solar heat through the PV / T plate fluctuates greatly with the seasons. However, this system makes full use of the strong adaptability of the environmentally friendly CO2 heat pump heat source through different operating conditions design. When the low-temperature heat pump working fluid is difficult to operate efficiently under low circulating water temperature conditions in winter, the CO2 heat pump is directly used to improve the quality of heat energy. This ensures that the circulating water can achieve stable cooling when flowing through the heat pump system under both winter and summer conditions. At the same time, it greatly reduces the impact of seasonal changes on the system's supply of domestic hot water, high-temperature water / steam, and cooling. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the combined cooling, heating and power system that couples photovoltaic, photothermal and heat pumps according to this application.

[0021] Figure 2 This is a schematic diagram of the combined cooling, heating and power system structure of the photovoltaic-thermal and heat pump coupling of this application.

[0022] Figure 3 This is a detailed schematic diagram of the low-temperature stage heat pump system in the combined cooling, heating and power system of this application.

[0023] Figure 4 For T h A schematic diagram of the system's operational components at temperatures above 35℃.

[0024] Figure 5 For T h A schematic diagram of the system's operational components at ≤35℃.

[0025] The meanings of the symbols marked in the figure are as follows: A-PV / T solar thermal cooling water system, B-CO2 heat pump system, C-low temperature heat pump system, D-high temperature heat pump system; 11-Cold water tank, 12-Circulation pump, 13-PV / T plate, 131-Battery, 14-Hot water tank, 15-Circulation water three-way valve, 151-First circulation water outlet, 152-Second circulation water outlet; 21-CO2 evaporator, 22-CO2 compressor, 23-CO2 three-way valve, 231-bypass CO2 outlet, 24-first-stage air cooler, 25-second-stage air cooler, 26-CO2 expansion valve; 31-Low-temperature stage evaporator, 32-Low-temperature stage compressor, 33-Condensing evaporator, 34-Low-temperature stage expansion valve; 41-Inlet three-way valve, 411-Bypass inlet, 412-Main pipeline inlet, 42-High temperature stage compressor, 43-Condenser, 431-First stage condenser, 432-Second stage condenser, 44-High temperature stage expansion valve, 45-Outlet three-way valve, 451-Bypass outlet, 452-Main pipeline outlet, 46-Medium temperature water three-way valve; 50 - Air-cooled evaporator, 501 - Hot side inlet, 502 - Hot side outlet; 60 - Refrigeration heat exchanger; a-Cold water end for the first user, b-Medium-temperature water end for the first user, c-High-temperature water end for the user, d-Cold water end for the second user, e-Hot water end for the second user, f-Cold water end for the third user, g-Hot water end for the third user. Detailed Implementation

[0026] The technical solution of the present invention will be described in more detail below with reference to the embodiments and accompanying drawings.

[0027] like Figure 1 and Figure 2 As shown, a photovoltaic-thermal-heat-heat-power cogeneration system coupled with a heat pump is characterized by comprising a PV / T solar thermal cooling water system A, a CO2 heat pump system B, a low-temperature heat pump system C, and a high-temperature heat pump system D.

[0028] PV / T solar thermal cooling water system A includes a cold water tank 11, a circulating pump (12), a PV / T plate 13, and a hot water tank 14 connected in sequence; CO2 heat pump system B includes a CO2 evaporator 21, a CO2 compressor 22, a CO2 three-way valve 23, a primary air cooler 24, a secondary air cooler 25, and a CO2 expansion valve 26 connected in sequence. The cold side inlet of the primary air cooler 24 is connected to the second user's cold water terminal D, and the cold side outlet of the primary air cooler 24 is connected to the second user's hot water terminal e. The cold side inlet of the secondary air cooler 25 is connected to the third user's cold water terminal f, and the cold side outlet of the secondary air cooler 25 is connected to the third user's hot water terminal g.

[0029] The low-temperature heat pump system C includes a low-temperature evaporator 31, a low-temperature compressor 32, a condenser-evaporator 33, and a low-temperature expansion valve 34 connected in sequence. The high-temperature heat pump system D includes an inlet three-way valve 41, a high-temperature compressor 42, a condenser 43, a high-temperature expansion valve 44, and an outlet three-way valve 45, which are sequentially connected in a self-condensing evaporator 33. The condenser 43 includes a primary condenser 431 and a secondary condenser 432 connected in series along the direction of the working fluid flow. The cold-side inlet of the secondary condenser 432 is connected to the first user's cold water end a, and the cold-side outlet of the secondary condenser 432 is connected to the cold-side inlet of the primary condenser 431 and the first user's medium-temperature water end b through a medium-temperature water three-way valve 46. The cold-side outlet of the primary condenser 431 is connected to the user's high-temperature water end c.

[0030] The outlet of the hot water tank 14 is connected to the circulating water three-way valve 15. The circulating water three-way valve 15 has two circulating water outlets. The second circulating water outlet 152 is connected to the CO2 evaporator 21, and the first circulating water outlet 151 is connected to the CO2 evaporator 21 via the low-temperature stage evaporator 31.

[0031] A refrigeration heat exchanger 60 is also installed between the CO2 evaporator 21 and the cold water tank 11. After the circulating water is cooled to chilled water by the hot side of the CO2 evaporator 21, it enters the refrigeration heat exchanger 60 to supply cooling to the user and then heats up before flowing into the cold water tank 11.

[0032] The low-temperature heat pump system C is coupled to the high-temperature heat pump system D through the condenser-evaporator 33.

[0033] The main inlets and outlets of the inlet three-way valve 41, outlet three-way valve 45, and CO2 three-way valve 23, which participate in the working fluid circulation of their respective systems, are defined as the main inlets and outlets. The third inlet and outlet are connected to the bypass, and are named bypass inlet 411, bypass outlet 451, and bypass CO2 outlet 231, respectively. A gas-cooled evaporator 50 is also provided between the bypass inlet 411 of the inlet three-way valve 41 and the bypass outlet 451 of the outlet three-way valve 45. The hot-side inlet 501 of the gas-cooled evaporator 50 is connected to the bypass CO2 outlet 231 of the CO2 three-way valve 23, and the hot-side outlet 502 of the gas-cooled evaporator 50 is connected to the inlet of the secondary gas cooler 25. To ensure that the heat from the air-cooled evaporator 50 can enter the condenser 43 through the inlet three-way valve 41, the inlet three-way valve 41 is connected to the main pipeline inlet 412 of the condenser-evaporator 33, and the outlet three-way valve 45 is connected to the main pipeline outlet 452 of the condenser-evaporator 33. It can also be automatically closed or a control valve can be used to prevent the working fluid in the air-cooled evaporator 50 from entering the condenser-evaporator 33.

[0034] Furthermore, in this application, the PV / T board 13 is also connected to a storage battery 131 for storing electrical energy. The storage battery 131 can be further connected to the electrical load end. This part is conventional technology in the field, and this application does not make any special limitations on it.

[0035] Based on the above, the control method for this photovoltaic-thermal-heat-power cogeneration system coupled with a heat pump is as follows: First, when the PV / T panel 13 in the solar thermal cooling water system A is activated by solar thermal energy, it enters the energy storage mode. At the same time, the real-time temperature T of the PV / T panel 13 is acquired. p When T p The starting temperature T of the solar thermal cooling water system A is greater than the set temperature. p,s When the PV / T plate 13 starts the circulating water cooling mode, the circulating water cooling operation time within the 24-hour operation cycle is recorded as t1; Then, within a 24-hour operating cycle, the total amount of working fluid m1 transferred from cold water tank 11 to hot water tank 14 in the circulating water cooling mode of the solar thermal cooling water system A is obtained, which is the product of the circulating water cooling operating time t1 and the average circulating water flow rate q1.

[0036] To prevent significant fluctuations in water flow rate during the maintenance of a reasonable temperature for the PV / T plate 13 in the circulating water cooling system, a reasonable initial circulating water flow rate needs to be determined. The initial circulating water flow rate is q. water The rated heat collection power P of the PV / T panel 13 can be used as a reference. heat The calculation is performed using the following formula: q water =P heat / (c water ·ΔT water ); In the formula, q water The unit is kg / s; P heat The unit is kW; c water ΔT is the specific heat capacity of the circulating cooling water, expressed in kJ / (kg·℃); water This is the theoretical temperature rise of the circulating cooling water, in °C. The values ​​are: 23°C when the daily maximum temperature is <25°C, and 33°C when the daily maximum temperature is ≥25°C.

[0037] When the circulating water cooling mode is started, the circulating pump 12 operates according to the initial circulating water flow rate q. water Once running, the water flow rate is further adjusted by the circulating pump 12 according to the temperature rise / fall.

[0038] Furthermore, based on user needs, the combined heating and cooling time t2 (i.e., the operating time of CO2 heat pump system B) within the 24-hour operating cycle is confirmed. During this time, the amount of working fluid transferred from hot water tank 14 to cold water tank 11, m2 = m1, is controlled to ensure that after the 24-hour operating cycle ends, cold water tank 11 has sufficient cold water to supply the next operating cycle. m2 is the product of the combined heating and cooling time t2 within the 24-hour operating cycle and the average flow rate q2 of the working fluid transferred from hot water tank 14 to cold water tank 11. Then, based on the water temperature T in hot water tank 14h Perform the following operations: When T h When the temperature is >35℃, the first circulating water outlet 151 of the circulating water three-way valve is opened, and the second circulating water outlet 152 of the circulating water three-way valve and the bypass CO2 outlet 231 of the CO2 three-way valve are closed. The hot water in the hot water tank 14 flows into the hot side of the low-temperature evaporator 31, cools down, and then enters the hot side of the CO2 evaporator 21 for further cooling. Finally, after passing through the refrigeration heat exchanger 60 to supply cooling capacity to the cold user, it enters the cold water tank 11. The working fluid of the high-temperature heat pump system D absorbs heat through the condenser evaporator 33, and then flows through the first-stage condenser 431 and the second-stage condenser 432 in sequence. In the second-stage condenser 432, the water from the first user's cold water end a is heated to medium-temperature water. The medium-temperature water is redistributed by the medium-temperature water three-way valve 46. Part of it is sent to the first user's medium-temperature water end b, and the other part enters the cold side inlet of the first-stage condenser 431. After being reheated by the first-stage condenser 431 to high-temperature water, it is sent to the user's high-temperature water end c. During this process, by adjusting the distribution ratio of the medium-temperature water three-way valve 46, the supply of medium-temperature water to the first user's medium-temperature water end b and the user's high-temperature water end c can be further adjusted.

[0039] The CO2 working fluid of CO2 heat pump system B absorbs heat through CO2 evaporator 21, heats the cold water from the second user cold water end D in the first-stage air cooler 24 and delivers it to the second user hot water end (e).

[0040] When T h When the temperature is ≤35℃, open the second circulating water outlet 152 of the circulating water three-way valve and the bypass CO2 outlet 231 of the CO2 three-way valve, and close the first circulating water outlet 151 of the circulating water three-way valve. The hot water in the hot water tank 14 flows into the hot side of the CO2 evaporator 21. After cooling, it enters the refrigeration heat exchanger 60 to provide cooling capacity to the user, and then enters the cold water tank 11. After the CO2 working fluid of the CO2 heat pump system B absorbs heat through the CO2 evaporator 21, part of it heats the cold water from the second user cold water end d in the first-stage air cooler 24 and delivers it to the second user hot water end e. The other part enters the hot side of the air-cooled evaporator 50 to release heat. After merging with the working fluid at the hot side outlet of the first-stage air cooler 24, it connects to the hot side inlet of the second-stage air cooler 25. The working fluid of the high-temperature heat pump system D absorbs heat through the air-cooled evaporator 50 and heats the water from the first user cold water end a in the condenser 43 to medium-temperature water and delivers it to the first user medium-temperature water end b and / or heats it to high-temperature water and delivers it to the user high-temperature water end c.

[0041] The start-up temperature T of the above-mentioned solar thermal cooling water system A p,s T is defined as: when the daily maximum temperature is <25℃. p,s When the temperature is set to 40℃ and the daily maximum temperature is ≥25℃, T p,s Set to 50℃.

[0042] Furthermore, the real-time temperature T of the PV / T plate 13 can be controlled by controlling the circulating water flow rate. p It operates within the efficient temperature range required for power generation. Specifically, monitoring... T p The change value within a set time period, when T p When the temperature rises beyond the maximum value of the set range within the set time, the speed of circulating pump 12 is adjusted to increase the circulating water flow rate by 10%; when T p If the temperature exceeds the maximum value of the set range within the set time, adjust the speed of circulation pump 12 to reduce the circulating water flow rate by 10%, until... T p The change value stabilizes within the set range over a set time period. Typically, the efficient operating temperature range required for power generation is below 50°C. In one specific embodiment, the set time interval is 5 minutes, the set range is 0~5°C, and the maximum value of the set range is 5°C.

[0043] Example 1 For a PV / T system with a collector capacity of 50 kW, under stable summer operation, assuming a hot water tank temperature of 45℃ and a cold water tank temperature of 12℃, with a circulating water flow rate of 0.36 kg / s and operating for 6 hours a day, the total amount of 45℃ hot water produced in one day is 7776 kg. Assuming the combined cooling and heating system operates for 6 hours, the heat source water flow rate through the heat pump system is 0.36 kg / s. At this time, the low-temperature stage working fluid is R134a, and the high-temperature stage working fluid is R245fa. The low-temperature stage heat pump system C lowers the hot water temperature to 35℃, and the CO2 heat pump system B lowers the hot water temperature from 35℃ to 7℃. After passing through the refrigeration heat exchanger 60 and supplying cooling, the water is heated to 12℃ before entering the cold water tank 11. The key component parameters, calculated through simulation, are as follows: Low-temperature stage evaporator 31, hot side inlet water 45℃, outlet water 35℃, cold side R134a evaporation temperature 32.8℃, load 15.03 kW; The condenser-evaporator 33 has an inlet temperature of 73.3℃ and an outlet temperature of 66.6℃ on the hot side (R134a), an evaporation temperature of 60℃ on the cold side (R245fa), and a load of 17.06 kW. The first-stage condenser is 431, R245fa, with a hot-side inlet temperature of 120.8℃ and an outlet temperature of 119.1℃. The cold-side water inlet temperature is 90℃ and the outlet temperature is 110℃ (for supplying high-temperature water to the user, end c), with a load of 7.24 kW. The secondary condenser 432 has an R245fa hot-side inlet temperature of 119.1℃ and an outlet temperature of 105.8℃. The cold-side water inlet temperature is 70℃ (for the first user's cold water end a) and the outlet temperature is 90℃ (for the first user's medium-temperature water end b or for the primary condenser 431). The load is 13.2 kW. 45% of the 90°C water at the outlet of the secondary condenser 432 is directly utilized by the first user's medium-temperature water end b, thus obtaining 0.26 t / h of circulating medium-temperature water (90°C supply water, 70°C return water), and 55% enters the primary condenser 431 to be further heated to 110°C, ultimately obtaining 0.31 t / h of circulating high-temperature water (110°C supply water, 90°C return water) (supplying the user's high-temperature water end c).

[0044] CO2 evaporator 21, hot side water inlet 35℃, outlet 7℃, cold side CO2 evaporation temperature 5℃, load 43.5kW; The first-stage air cooler has a temperature of 24°C, with a CO2 inlet temperature of 112.5°C and an outlet temperature of 65°C on the hot side, and a water inlet temperature of 50°C and an outlet temperature of 70.4°C on the cold side. The load is 25.05kW. The secondary air cooler is 25, with a hot-side CO2 inlet temperature of 65℃ and an outlet temperature of 38.8℃, and a cold-side water inlet temperature of 20℃ (tap water, third user cold water end f) and an outlet temperature of 50℃ (third user hot water end g), with a load of 36.71kW. When operating independently, the first-stage air cooler 24 obtains 1.02 t / h of circulating hot water (70.4℃ supply water, 50℃ return water) to supply the second user's hot water end e, and the second-stage air cooler 25 obtains 1.02 t / h of 50℃ domestic hot water to supply the third user's hot water end f.

[0045] In this embodiment, the cold sides of the primary air cooler 24 and the secondary air cooler 25 can be connected in series, that is, the cold side outlet of the secondary air cooler 25 is connected to the cold side inlet of the primary air cooler 24. At this time, the second user is no longer supplied, and only the third user is supplied, so 1.02t / h of hot water at 70.4℃ can be supplied to the hot water end e of the second user.

[0046] The refrigeration heat exchanger 60 has a cold side water inlet temperature of 7℃ and an outlet temperature of 12℃, providing cooling to users with a load of 7.77kW.

[0047] Example 2 For a PVT system with a collector power of 35 kW, during stable operation in winter, assuming a hot water tank temperature of 35℃ and a cold water tank temperature of 12℃, the circulating water flow rate is calculated to be 0.36 kg / s. Operating for 6 hours a day, the total amount of 45℃ hot water produced in one day is 7776 kg. Assuming the combined cooling and heating system operates for 6 hours, the heat source water flow rate through the heat pump system is 0.36 kg / s. At this time, the low-temperature stage heat pump system C is shut down, the high-temperature stage working fluid is R245fa, and the CO2 heat pump system B reduces the hot water temperature from 35℃ to 7℃. Part of the CO2 from the outlet of the CO2 compressor 22 flows through the first-stage air cooler 24 and the second-stage air cooler 25, while the other part flows through the air-cooled evaporator 50 to supply heat to the high-temperature stage heat pump system D. The key component parameters, calculated through simulation, are as follows: CO2 evaporator 21, hot side water inlet 35℃, outlet 7℃, cold side CO2 evaporation temperature 5℃, load 43.5 kW; The secondary air cooler 25 has a CO2 inlet temperature of 65℃ and an outlet temperature of 38.8℃ on the hot side, and a water inlet temperature of 20℃ (for the third user's cold water end f) and an outlet temperature of 50℃ (for the third user's hot water end g). With a load of 36.71 kW, it can provide 1.02 t / h of domestic hot water at 50℃.

[0048] The first-stage air cooler 24 has a hot-side CO2 inlet temperature of 112.5℃ and an outlet temperature of 65℃, a cold-side water inlet temperature of 50℃ (second user cold water end d) and an outlet temperature of 70.4℃ (second user hot water end e), a load of 8kW, and can obtain 0.32 t / h of circulating hot water (70.4℃ supply water, 50℃ return water). The air-cooled evaporator is 50, with a hot-side CO2 inlet temperature of 112.5℃ and an outlet temperature of 65℃, and a cold-side R245fa evaporation temperature of 60℃, with a load of 17.06 kW. The first-stage condenser is 431, R245fa, with a hot-side inlet temperature of 120.8℃ and an outlet temperature of 119.1℃, and a cold-side water inlet temperature of 90℃ and an outlet temperature of 110℃, with a load of 7.24 kW. The two-stage condenser is a 432 model, made of R245fa steel. The hot side inlet temperature is 119.1℃ and the outlet temperature is 105.8℃. The cold side water inlet temperature is 70℃ and the outlet temperature is 90℃. The load is 13.2 kW. 45% of the 90°C water from the outlet of the secondary condenser 432 is directly used by the first user's medium-temperature water end b, and 55% enters the primary condenser 431 for further heating to 110°C. Finally, 0.31 t / h of circulating high-temperature water (110°C supply water, 90°C return water) is supplied to the user's high-temperature water end c, and 0.26 t / h of circulating medium-temperature water (90°C supply water, 70°C return water) is supplied to the first user's medium-temperature water end b.

[0049] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A combined cooling, heating and power system coupling photovoltaic thermal energy and a heat pump, characterized in that, Including PV / T solar thermal cooling water system (A), CO2 heat pump system (B), low temperature heat pump system (C) and high temperature heat pump system (D); The PV / T solar thermal cooling water system (A) includes a cold water tank (11), a circulating pump (12), a PV / T plate (13), and a hot water tank (14) connected in sequence; the CO2 heat pump system (B) includes a CO2 evaporator (21), a CO2 compressor (22), a CO2 three-way valve (23), a primary air cooler (24), a secondary air cooler (25), and a CO2 expansion valve (26) connected in sequence; the low-temperature heat pump system (C) includes a low-temperature evaporator (31), a low-temperature compressor (32), a condenser evaporator (33), and a low-temperature expansion valve (34) connected in sequence. The outlet of the hot water tank (14) is connected to a circulating water three-way valve (15), the second circulating water outlet (152) of the circulating water three-way valve (15) is connected to the CO2 evaporator (21), and the first circulating water outlet (151) is connected to the CO2 evaporator (21) via the low-temperature stage evaporator (31); the low-temperature stage heat pump system (C) is coupled to the high-temperature stage heat pump system (D) through the condenser evaporator (33), and the high-temperature stage heat pump system (D) includes an inlet three-way valve (41) that is sequentially connected to the condenser evaporator (33), and a high-temperature stage heat pump system (D). The system includes a high-temperature stage compressor (42), a condenser (43), a high-temperature stage expansion valve (44), and an outlet three-way valve (45). A gas-cooled evaporator (50) is also provided between the bypass inlet (411) of the inlet three-way valve (41) and the bypass outlet (451) of the outlet three-way valve (45). The hot side inlet (501) of the gas-cooled evaporator (50) is connected to the bypass CO2 outlet (231) of the CO2 three-way valve (23), and the hot side outlet (502) of the gas-cooled evaporator (50) is connected to the hot side inlet of the secondary gas cooler (25). In the high-temperature heat pump system (D), the condenser (43) includes a primary condenser (431) and a secondary condenser (432) connected in series along the working fluid flow direction. The cold-side inlet of the secondary condenser (432) is connected to the first user's cold water end (a), and the cold-side outlet of the secondary condenser (432) is connected to the cold-side inlet of the primary condenser (431) and the first user's medium-temperature water end (b) respectively through a medium-temperature water three-way valve (46). The cold-side outlet of the primary condenser (431) is connected to the user's high-temperature water end (c).

2. The photovoltaic-thermal-heat-power cogeneration system coupled with a heat pump as described in claim 1, characterized in that, In the CO2 heat pump system (B), the cold-side inlet of the first-stage air cooler (24) is connected to the second user's cold water end (d), the cold-side outlet of the first-stage air cooler (24) is connected to the second user's hot water end (e), the cold-side inlet of the second-stage air cooler is connected to the third user's cold water end (f), and the cold-side outlet of the second-stage air cooler (25) is connected to the third user's hot water end (g).

3. A combined cooling, heating, and power system coupling photovoltaic thermal energy and a heat pump as described in claim 1, characterized in that, A refrigeration heat exchanger (60) is also provided between the CO2 evaporator (21) and the cold water tank (11). After the circulating water is cooled to chilled water by the hot side of the CO2 evaporator (21), it enters the refrigeration heat exchanger (60) to supply cooling to the user and heat up before flowing into the cold water tank (11).

4. A combined cooling, heating, and power system coupling photovoltaic thermal energy and a heat pump as described in claim 1, characterized in that, The PV / T board (13) is also connected to a battery (131) for storing electrical energy.

5. A control method for a photovoltaic-thermal-heat-power cogeneration system coupled with a heat pump as described in any one of claims 1-4, characterized in that, When the PV / T plate (13) in the solar thermal cooling water system (A) is activated by solar thermal energy, it enters the energy storage mode. At the same time, the real-time temperature T of the PV / T plate (13) is acquired. p When T p The starting temperature T of the solar thermal cooling water system (A) is greater than the set value. p,s When the PV / T board (13) starts the circulating water cooling mode, the circulating water cooling operation time within the 24-hour operation cycle is recorded as t1; Includes the following steps: S1. During a 24-hour operating cycle, obtain the total amount of working fluid m1 transferred from the cold water tank (11) to the hot water tank (14) in the circulating water cooling mode of the solar thermal cooling water system (A), which is the product of the circulating water cooling operation time t1 and the average circulating water flow rate q1; control the amount of working fluid m2 transferred from the hot water tank (14) to the cold water tank (11) during the 24-hour operating cycle to be equal to m1, where m2 is the product of the combined cooling and heating time t2 during the 24-hour operating cycle and the average flow rate q2 of the working fluid transferred from the hot water tank (14) to the cold water tank (11), and the combined cooling and heating time t2 is the operating time of the CO2 heat pump system B; S2. Obtain the water temperature T in the hot water tank (14) h When T h When the temperature is >35℃, the first circulating water outlet (151) of the circulating water three-way valve is opened, and the second circulating water outlet (152) of the circulating water three-way valve and the bypass CO2 outlet (231) of the CO2 three-way valve are closed. The hot water in the hot water tank (14) flows into the hot side of the low-temperature stage evaporator (31), cools down, and then enters the hot side of the CO2 evaporator (21) for further cooling. Finally, after passing through the refrigeration heat exchanger (60) to supply cooling capacity to the cold user, it enters the cold water tank (11); the high-temperature stage heat pump system ( The working fluid of D) absorbs heat through the condenser-evaporator (33), and in the condenser (43) heats the water from the first user's cold water end (a) into medium-temperature water and delivers it to the first user's medium-temperature water end (b) and / or heats it into high-temperature water and delivers it to the user's high-temperature water end (c); the CO2 working fluid of the CO2 heat pump system (B) absorbs heat through the CO2 evaporator (21), and in the first-stage air cooler (24) heats the cold water from the second user's cold water end (d) and delivers it to the second user's hot water end (e). When T h When the temperature is ≤35℃, open the second circulating water outlet (152) of the circulating water three-way valve and the bypass CO2 outlet (231) of the CO2 three-way valve, and close the first circulating water outlet (151) of the circulating water three-way valve. The hot water in the hot water tank (14) flows into the hot side of the CO2 evaporator (21), and after cooling, it enters the refrigeration heat exchanger (60) to provide cooling capacity to the user, and then enters the cold water tank (11). The CO2 working fluid of the CO2 heat pump system (B) passes through the CO2 evaporator (21) and the CO2 compressor (231). 2) After heating, part of the cold water from the second user's cold water end (d) is heated in the first-stage air cooler (24) and delivered to the second user's hot water end (e), while the other part enters the hot side of the air-cooled evaporator (50) to release heat. The working fluid of the high-temperature heat pump system (D) absorbs heat through the air-cooled evaporator (50) and heats the water from the first user's cold water end (a) into medium-temperature water in the condenser (43) and delivers it to the first user's medium-temperature water end (b) and / or heats it into high-temperature water and delivers it to the user's high-temperature water end (c).

6. The control method for a photovoltaic-thermal-heat-power cogeneration system coupled with a heat pump as described in claim 5, characterized in that, The real-time temperature T of the PV / T plate (13) is controlled by controlling the circulating water flow rate. p It is within the efficient operating temperature range required for power generation; specifically, monitoring... T p The change value within a set time period, when T p When the temperature rises above the maximum value of the set range within the set time, the speed of the circulating pump (12) is adjusted to increase the circulating water flow rate by 10%; when T p If the temperature drop exceeds the maximum value of the set range within the set time, adjust the speed of the circulating pump (12) to reduce the circulating water flow rate by 10%, until... T p The change value stabilizes within the set range within a set time period; the set time interval is 5 min, and the set range is 0~5℃.

7. The control method for a photovoltaic-thermal-heat-power cogeneration system coupled with a heat pump as described in claim 6, characterized in that, Initial circulating water flow rate q water According to the rated heat collection power P of the PV / T panel (13) heat The calculation is performed using the following formula: what water =P heat / (c water ·ΔT water ); In the formula, q water The unit is kg / s; P heat The unit is kW; c water ΔT is the specific heat capacity of the circulating cooling water, expressed in kJ / (kg·℃); water This is the theoretical temperature rise of the circulating cooling water, in °C. The values ​​are set as follows: 23°C when the daily maximum temperature is <25°C, and 33°C when the daily maximum temperature is ≥25°C.

8. The control method for a photovoltaic-thermal-heat-power cogeneration system coupled with a heat pump as described in claim 6, characterized in that, The power generation requires an efficient operating temperature of ≤50℃; the start-up temperature T of the solar thermal cooling water system (A) is required when the daily maximum temperature is <25℃. p,s The start-up temperature T of the photothermal cooling water system (A) is set at 40℃, with a daily maximum temperature ≥25℃. p,s Set to 50℃.

9. The control method for a photovoltaic-thermal-heat-power cogeneration system coupled with a heat pump as described in claim 5, characterized in that, The supply of medium-temperature water to the first user's medium-temperature water end (b) and the user's high-temperature water end (c) is adjusted by regulating the flow ratio of the medium-temperature water three-way valve (46).

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