Solar coupling transcritical CO2 two-stage heat pump system suitable for cold region

Abstract

The invention discloses a solar coupling transcritical CO2 two-stage heat pump system suitable for heating and domestic hot water in a cold region. The problems that existing heating equipment is high in energy consumption, low in efficiency and the like are solved. The system takes a PVT photovoltaic-photo-thermal heat collector as a core, and combines photoelectric and photo-thermal dual collection: the PVT heat collector is provided with a fan for heat dissipation, and power can be generated for a heat pump compressor to use; the photoelectric part and the PVT heat collector are additionally provided with fans for heat dissipation, generated power can supply power to a heat pump compressor, and when the heat pump system and the PVT operate together, cold air blown out by an evaporator of the heat pump system can cool the PVT. And the photo-thermal part supplies heat to the domestic hot water tank and the floor heating water tank. When solar energy is insufficient, the transcritical CO2 heat pump is started, and a refrigerant flows through all parts to provide hot water for domestic hot water and a heating water tank. According to the system, the working modes are intelligently switched, light-electricity-heat cooperation is optimized, the requirements of near-zero-energy-consumption buildings in severe cold areas are met, the energy efficiency ratio is increased, and efficient and energy-saving operation is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to a solar energy coupled transcritical CO2 heat pump system, particularly suitable for heating and refrigeration in cold regions, aiming to provide an efficient near zero energy consumption heat pump system, and combining solar energy with CO2 heat pump technology to solve the problems of high energy consumption and high emissions of traditional heating methods in cold regions. BACKGROUND

[0002] At present, the heating system in cold regions generally uses coal, gas and resistance heating methods, which has the problems of high energy consumption and low efficiency, resulting in high energy consumption, serious greenhouse gas emissions and environmental impact. The traditional heat pump system also has the problems of low efficiency at low temperature and high operating cost.

[0003] Solar energy has great potential for use in cold regions, but the single solar water heating system has a sharp decline in heat collection efficiency under snow and extreme cold conditions, and is limited by the ambient temperature. The efficiency of using solar energy alone is low.

[0004] At present, there is still a lack of a system that can use solar photovoltaic, photothermal and transcritical CO2 heat pump technology in severe cold environments, and due to the good properties of natural working medium CO2, such as ODP=0, GWP=1, non-toxic and non-flammable, it can realize efficient, low-energy and low-carbon emission of all-weather stable heating and domestic hot water. Therefore, it is imperative to develop a system that can efficiently use solar photothermal and photovoltaic and transcritical CO2 heat pump technology, and effectively improve energy use efficiency and reduce carbon emissions, which has important environmental protection and energy saving significance. SUMMARY

[0005] The present application provides a solar energy coupled transcritical carbon dioxide heat pump near zero energy consumption system suitable for cold regions, aiming to solve the problems of low operating efficiency, insufficient energy utilization and high system energy consumption of existing heating devices under extreme low temperature conditions. The system couples a PVT photovoltaic and photothermal collector with a transcritical CO2 two-stage compression heat pump system, fully utilizes the solar energy resource energy recovery mechanism, realizes efficient supply of domestic hot water and heating, and has the advantages of flexible operating mode, low energy consumption and adaptability to various meteorological conditions, and is suitable for heating and hot water application scenarios of residential buildings, office buildings and other buildings in severe cold regions.

[0006] The present application solves the above technical problems by the following technical solutions:

[0007] The overall system structure of the application comprises: a PVT collector, a fan, a photovoltaic controller, a storage battery, an inverter, a low-pressure compressor, a high-pressure compressor, an evaporator, an expander, a flash evaporator, an air cooler, a domestic hot water tank, a heating hot water tank, and a user-side terminal device. The PVT collector has both photovoltaic power generation and photothermal collection functions, and is connected to the photovoltaic controller and the storage battery through a circuit. The output end of the storage battery is connected to the inverter, and the inverter outputs alternating current to provide driving energy for the CO2 low-pressure compressor and the high-pressure compressor.

[0008] The hot water end of the PVT collector is connected to the domestic hot water tank and the heating hot water tank, respectively, and the photothermal energy can directly heat the water in the hot water tank for domestic hot water and floor heating. When only the PVT collector is running, the fan powered by the storage battery forcibly cools the surface of the PVT collector to improve the photoelectric conversion efficiency. When the CO2 heat pump system and the PVT collector are running cooperatively, the cold air discharged from the evaporator can also be used to cool the PVT collector, thereby realizing integrated energy efficiency improvement in the electric-thermal cooperative running state.

[0009] The working medium circuit of the CO2 heat pump system comprises, in sequence: an evaporator outlet connected to a low-pressure compressor inlet, a low-pressure compressor outlet connected to a flash evaporator, a flash evaporator used to increase the subcooling degree of the refrigerant before throttling to improve the heat absorption capacity of the evaporator in a low-temperature environment, a flash evaporator outlet connected to a high-pressure compressor inlet, a high-pressure compressor outlet connected to an air cooler through a pipeline, a high-temperature air cooler and a low-temperature air cooler connected to a domestic hot water tank and a heating hot water tank, respectively, to ensure that different temperature hot water is provided for users to meet the heating and daily hot water demand, and an expander coaxially connected to the high-pressure and low-pressure compressors, respectively, to recover the expansion work and realize energy recovery and utilization. The system can realize intelligent switching of multiple working conditions through a three-way valve or an electrically controlled switching device.

[0010] The application has the following beneficial effects through the multi-energy complementary and cooperative design of the PVT and the transcritical CO2 heat pump: 1) solar photovoltaic-photothermal resources are used to simultaneously provide heat and power for users; 2) the flash evaporator is used to increase the CO2 subcooling degree and enhance the heating capacity, which is suitable for operation in extremely cold environments; 3) the expander is used to recover the expansion work and reduce the energy consumption of the system; and 4) multiple operating modes can be automatically switched according to the weather and user load to realize system energy efficiency optimization and near-zero energy consumption operation. BRIEF DESCRIPTION OF DRAWINGS

[0011] The application will be further described below in combination with the drawings and examples.

[0012] Figure 1 is a flowchart of the application.

[0013] In the figure: 1-PVT collector, 2-evaporator, 3-fan, 4-battery, 5-photovoltaic controller, 6-inverter, 7-low pressure compressor, 8-high pressure compressor, 9-low temperature gas cooler, 10-high temperature gas cooler, 11, 13-expander, 12-flash evaporator, 14-hot water tank, 15, 16-user end, 17-heating hot water tank, 18-floor heating coil. DETAILED DESCRIPTION

[0014] In the sunny day, PVT collector (1) absorbs solar energy to generate electricity and heat, photovoltaic electricity is adjusted by controller (5) and stored in battery (4), and is supplied to compressor (7) (8) and fan (3) to dissipate heat of PVT through inverter (6), and the heat of the light and heat side is simultaneously transmitted to hot water tank (14) and heating water tank (17).

[0015] If the heat load is large or the sunlight intensity is weak, the controller automatically starts the CO2 heat pump system, the low pressure compressor (7) compresses the refrigerant, and after the supercooling treatment of the flash evaporator (12), the high pressure compressor (8) continues to compress, the gas cooler (9) and the gas cooler (10) provide the required heat for the hot water tank (14) and the heating hot water tank (17) respectively, and the expanders (11) (13) are coaxially connected with the high pressure stage compressor (8) and the low pressure stage compressor (7) respectively, to provide the recovered energy for the compressor, so as to improve the energy efficiency of the system.

[0016] During the operation of the evaporator (2), cold air is generated and blown to the back of the PVT collector (1), and the fan cooperates to complete the cooling of the component and improve the overall efficiency; if it is extremely cold at night or in snowy weather, the system switches to pure heat pump mode to ensure uninterrupted hot water and heating.

[0017] The embodiment of the application has reasonable structure and flexible operation strategy, and is particularly suitable for promotion and application in places such as residences, office buildings and the like in severe cold and complex climate areas.

Claims

1. A solar coupled transcritical CO2 heat pump near zero energy consumption system suitable for cold regions, characterized in that, It comprises a refrigerant pipeline, a circulating water pipeline and a photovoltaic-photothermal composite PVT collector; the solar photothermal collector is used for coupling photovoltaic power generation and hot water collection; the refrigerant pipeline is connected with the PVT collector, an expander (11) (13), a high-pressure stage compressor (8) and a low-pressure stage compressor (7) coaxially, a flash evaporator (12), a low-temperature gas cooler (10) and a high-temperature gas cooler (9) in sequence; and the output ends of the gas coolers are connected with a heating hot water tank (17) and a user's domestic hot water tank (14) through the circulating water pipeline.

2. The system of claim 1, wherein, The circulating water pipeline comprises water inlets and outlets of the domestic hot water tank (14) and the heating hot water tank (17), the PVT collector is connected with the water inlets and outlets of the domestic and heating water tanks to realize storage and release of solar waste heat.

3. The system of claim 1 or 2, wherein, The flash evaporator (12) is arranged between the outlet of the low-pressure stage compressor and the inlet of the high-pressure stage compressor, and is used for increasing the supercooling degree of the transcritical CO2 refrigerant to improve the overall heating capacity at low ambient temperature.

4. The system of claim 1, wherein, The PVT collector is further provided with a fan (3), when the PVT collector is operated alone, a storage battery (4) supplies power to the fan (3) to actively cool the surface of the collector to improve the efficiency of the photovoltaic module; when the heat pump system and the PVT collector are operated cooperatively, the cold air released by the evaporator (2) is used for cooling the PVT collector (1) to reduce the temperature of the module and improve the comprehensive efficiency of the system.

5. The system of claim 1, wherein, The PVT collector power generation device drives the low-pressure stage compressor (7) and the high-pressure stage compressor (8) via conversion of photovoltaic controller (5), storage battery (4) and inverter (6) into alternating current, and the excess power is supplied to daily power load outside the inverter.

6. The system of claim 1, wherein, The low-temperature gas cooler (10) provides 45℃ hot water to the heating hot water tank (17), the high-temperature gas cooler (9) provides 60℃ hot water to the domestic hot water tank (14), the heating hot water tank (17) is connected with a floor heating coil (18) downstream to use hot water for building floor heating, and the domestic hot water tank (14) is externally provided with domestic water inlets (15.16) for delivery and use of domestic hot water to meet different needs of users.

7. The system according to the preceding claim 1, characterized in that, The expander (11) (13) coaxially connected with the high-pressure stage compressor (8) and the low-pressure stage compressor (7) is further included, the expander is used for energy recovery of the carbon dioxide refrigerant before and after throttling, and the recovered energy is coaxially fed back to the high and low pressure compressors to improve the system efficiency and reduce the energy consumption.

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