Fused salt energy storage coupled CO2 air source heat pump water heater cascade energy storage and steam supply system

Abstract

A fused salt energy storage coupled CO2 air source heat pump water heater cascade energy storage steam supply system comprises a first-stage energy storage system and a second-stage energy storage system, the first-stage energy storage system comprises a softened water tank, and a water inlet of the softened water tank is connected with a water outlet of a softened water treatment device through a water conveying pipeline; a water outlet of the softened water tank is connected with a water inlet of a heated channel of a condenser of the carbon dioxide air source heat pump water heater through a softened water pipe connected with a softened water pump in series, and a water outlet of the heated channel of the condenser is connected with a water inlet of the heat storage water tank through a first-stage hot water pipe. A high-temperature and high-pressure gaseous carbon dioxide inlet of the heat dissipation channel of the condenser is connected with a circulating medium outlet of the carbon dioxide compressor through a pipeline. According to the cascade energy storage and steam supply system of the fused salt energy storage coupled CO2 air source heat pump water heater, the electricity price advantage of electricity in the off-peak period is fully utilized, the operation cost of a steam supply system of an enterprise can be reduced, and finished steam with the lower cost is provided for the enterprise.

Description

Technical Field

[0001] The present invention relates to, in particular to a molten salt energy storage coupled with CO 2 Air source heat pump water heater cascade energy storage steam supply system. Background Art

[0002] Molten salt energy storage is a new energy storage technology that uses a mixture of molten (liquid) nitrates, chlorides and carbonates in a certain proportion as a storage and heat transfer medium to store excess solar energy, electricity, high-temperature steam and flue gas in the form of sensible heat, and when needed, it combines the heat exchange system to output high-temperature steam to drive the steam turbine for power generation or direct heating. Compared with electrochemical energy storage, molten salt energy storage has many advantages such as low construction cost, long service life, no efficiency attenuation, suitability for large-scale, and environmental safety. It can be applied to many fields such as solar thermal power generation, clean heating, industrial steam supply and flexibility transformation of thermal power units.

[0003] In chemical, food processing, pharmaceutical, steel and petrochemical enterprises, production requires a large amount of steam, and due to production needs, condensate water is often unable to be recycled. At present, steam is mainly obtained by purchasing from outside, or by using gas boilers, electric steam boilers and other methods. Purchased steam needs to be transported to the factory through a long-distance steam pipeline network, and the price of steam is often high; using gas boilers to produce steam requires natural gas as fuel, which consumes a large amount of natural gas, not only causing environmental problems, but also high costs; using electric boilers to directly generate steam consumes a large amount of electricity and the electricity price is high, so the cost of steam is also high.

[0004] In order to solve the high cost of obtaining steam for chemical enterprises and the environmental problems of using gas boilers to supply steam, the present invention proposes a method of using valley electricity energy storage coupled with CO 2 Air source heat pump water heater cascade energy storage steam supply system. Summary of the invention

[0005] The purpose of the present invention is to provide a molten salt energy storage coupled CO2-free steam generator that can reduce the operating cost of the enterprise's steam supply system by making full use of the electricity price advantage during off-peak hours and provide the enterprise with lower-cost finished steam. 2 Air source heat pump water heater cascade energy storage steam supply system.

[0006] The molten salt energy storage coupled with CO 2The cascade energy storage steam supply system of the air source heat pump water heater comprises a primary energy storage system and a secondary energy storage system, wherein the primary energy storage system comprises a softened water tank, the water inlet of the softened water tank is connected to the water outlet of the softened water treatment device through a water delivery pipeline, the water outlet of the softened water tank is connected to the water inlet of the heating channel of the condenser of the carbon dioxide air source heat pump water heater through a softened water pipe connected in series with a soft water pump, the water outlet of the heating channel of the condenser is connected to the water inlet of the hot water storage tank through a primary hot water pipe, the high-temperature and high-pressure gaseous carbon dioxide inlet of the heat dissipation channel of the condenser is connected to the circulating medium outlet of the carbon dioxide compressor through a pipeline, the circulating medium inlet of the carbon dioxide compressor is connected to the outlet of the heating channel of the regenerator through a high-temperature and low-pressure gaseous carbon dioxide pipeline, the inlet of the heating channel of the regenerator is connected to the medium outlet of the evaporator through a pipeline, the medium inlet of the evaporator is connected to the outlet of the heat dissipation channel of the regenerator through a pipeline connected in series with an expansion valve, and the inlet of the heat dissipation channel of the regenerator is connected to the outlet of the heat dissipation channel of the condenser through a liquid carbon dioxide delivery pipeline;

[0007] The secondary energy storage system includes a molten salt electric heater, the outlet of the molten salt electric heater is connected to the inlet of a high-temperature molten salt storage tank through a high-temperature molten salt delivery pipe, the outlet of the high-temperature molten salt storage tank is connected to the inlet of a heat dissipation channel of an evaporator through a high-temperature molten salt pipeline connected in series with a high-temperature molten salt pump, the outlet of the heat dissipation channel of the evaporator is connected to the inlet of a low-temperature molten salt storage tank through a low-temperature molten salt pipeline, the outlet of the low-temperature molten salt storage tank is connected to the inlet of the molten salt electric heater through a low-temperature molten salt delivery pipe, and a low-temperature molten salt pump is connected in series to the low-temperature molten salt delivery pipe;

[0008] The outlet of the heating channel of the evaporator is connected to the inlet of the high-temperature steam pipeline, the inlet of the heating channel of the evaporator is connected to the outlet of the deoxygenated water delivery pipeline, a valve and a secondary pressurized water pump are connected in series on the deoxygenated water delivery pipeline, the inlet of the deoxygenated water delivery pipeline is connected to the water outlet of the deaerator, the water inlet of the deaerator is connected to the water outlet of the hot water storage tank through a hot water delivery pipe, and a primary pressurized water pump is connected in series on the hot water delivery pipe.

[0009] Preferably, the high-temperature steam pipeline is connected to the steam outlet of the electrode boiler or electric heater through a backup steam pipeline with a valve in series, and the water inlet of the electrode boiler or electric heater is connected to the water outlet section of the secondary pressurized water pump on the deoxygenated water delivery pipeline through a water supply pipeline with a valve in series.

[0010] Preferably, the high-temperature steam pipeline is connected to the water inlet of the deaerator through a branch pipeline with a valve in series.

[0011] Preferably, the outlet of the high-temperature molten salt storage tank is connected to the inlet of the heat dissipation channel of the evaporator through a spare high-temperature molten salt pipeline connected in series with a spare high-temperature molten salt pump, and the outlet of the low-temperature molten salt storage tank is connected to the inlet of the molten salt electric heater through a spare low-temperature molten salt delivery pipe connected in series with a spare low-temperature molten salt pump.

[0012] Preferably, the softening water pipe is connected to the primary hot water pipe via a bypass pipe with a valve in series.

[0013] Preferably, the outlet water temperature of the heating channel of the condenser does not exceed 95°C, the temperature of the high-temperature molten salt circulating in the secondary energy storage system is 400°C-425°C, and the temperature of the low-temperature molten salt is 200°C-230°C, and the molten salt filled in the molten salt electric heater, the high-temperature molten salt storage tank and the low-temperature molten salt storage tank is a ternary mixed nitrate.

[0014] Preferably, the ternary mixed nitrate is composed of 53% by weight of KNO 3 , 40% by weight NaNO 3 and 7% by weight NaNO 3 constitute.

[0015] Preferably, the electrode boiler or the electric heater is turned on to produce steam during the low electricity consumption period, and the evaporator does not produce steam during the low electricity consumption period.

[0016] The molten salt energy storage coupled with CO 2 The air source heat pump water heater cascade energy storage steam supply system has the following beneficial effects:

[0017] 1. Generating steam through cascade energy storage heating reduces the amount of molten salt used in simple molten salt energy storage, while also reducing the volume of the molten salt tank, thereby reducing the initial investment of the system.

[0018] Second, make full use of valley electricity and use CO2 air source heat pump water heater to heat the low temperature section, which saves energy and further reduces the energy cost of steam.

[0019] 3. Using valley electricity cascade energy storage heating to provide steam for industrial enterprises solves the environmental problems of the existing technology of using gas boilers to supply steam, as well as the problem of excessive cost fluctuations due to unstable natural gas prices;

[0020] Fourth, enterprises use energy storage systems to directly generate steam, which reduces pipeline network investment, reduces energy loss of steam along the pipeline network, and saves energy compared to purchasing steam from outside;

[0021] 5. Making full use of valley electricity storage during low-peak electricity consumption is beneficial to shifting peak power into valley power and increasing the absorption of new energy electricity.

[0022] In summary, the technical solution of the present invention makes full use of the characteristics of water and molten salt media, adopts cascade energy storage heating technology to produce steam, and achieves the effect of energy saving and cost reduction to the greatest extent; at the same time, the technical solution of the present invention adopts CO 2 The air source heat pump water heater combines the hot water storage tank with the molten salt system for two-stage energy storage, which can save more than 9% of energy compared with the simple molten salt energy storage. 2 The air source heat pump water heater cascade energy storage steam supply system has the advantages of making full use of the electricity price advantage during off-peak hours, has high energy efficiency, can minimize the operating costs of the enterprise's steam supply system, and provide the enterprise with lower-cost finished steam.

[0023] The present invention is described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The molten salt energy storage coupled with CO 2 Working principle diagram of the cascade energy storage steam supply system of the air source heat pump water heater. DETAILED DESCRIPTION

[0025] like Figure 1 As shown, the molten salt energy storage of the present invention is coupled with CO 2 The cascade energy storage steam supply system of the air source heat pump water heater comprises a primary energy storage system and a secondary energy storage system. The primary energy storage system comprises a softened water tank 1. The water inlet of the softened water tank 1 is connected to the water outlet of the softened water treatment device 32 through a water delivery pipeline. The water outlet of the softened water tank 1 is connected to the water inlet of the heating channel of the condenser 4 of the carbon dioxide air source heat pump water heater through a softened water pipe 3 connected in series with a soft water pump 2. The water outlet of the heating channel of the condenser 4 is connected to the water inlet of the hot water storage tank 6 through a primary hot water pipe 5. The high-temperature and high-pressure gaseous carbon dioxide inlet of the heat dissipation channel of the condenser 4 is connected to the carbon dioxide pressure tank 6 through a pipeline. The circulating medium outlet of the compressor 7 is connected, the circulating medium inlet of the carbon dioxide compressor 7 is connected to the outlet of the heating channel of the regenerator 9 through the high-temperature and low-pressure gaseous carbon dioxide pipeline 8, the inlet of the heating channel of the regenerator 9 is connected to the medium outlet of the evaporator 10 through a pipeline, the medium inlet of the evaporator 10 is connected to the outlet of the heat dissipation channel of the regenerator 9 through a pipeline connected in series with an expansion valve 11, and the inlet of the heat dissipation channel of the regenerator 9 is connected to the outlet of the heat dissipation channel of the condenser 4 through a liquid carbon dioxide delivery pipeline 12; in order to achieve the lowest operating cost, the carbon dioxide air source heat pump water heater is operated during the off-peak period of electricity consumption.

[0026] When in use, tap water from the outside can first enter the softening water treatment device 32. After being softened in the softening water treatment device 32, the tap water enters the softened water tank 1, and then is transported to the water inlet of the heating channel of the condenser 4 of the carbon dioxide air source heat pump water heater through the soft water pump 2 and the softening water pipe 3. The electricity used to heat the softened water in the heating channel is the electricity during the low electricity consumption. After the softened water in the heating channel of the condenser 4 is heated, it enters the hot water storage tank 6 for storage and standby, and completes the first-level energy storage heating process. The amount of hot water stored in the hot water storage tank must meet the system's daily water demand.

[0027] The secondary energy storage system includes a molten salt electric heater 20, the outlet of the molten salt electric heater 20 is connected to the inlet of a high-temperature molten salt storage tank 21 through a high-temperature molten salt delivery pipe 35, the outlet of the high-temperature molten salt storage tank 21 is connected to the inlet of a heat dissipation channel of an evaporator 24 through a high-temperature molten salt pipeline 23 connected in series with a high-temperature molten salt pump 22, the outlet of the heat dissipation channel of the evaporator 24 is connected to the inlet of a low-temperature molten salt storage tank 26 through a low-temperature molten salt pipeline 25, the outlet of the low-temperature molten salt storage tank 26 is connected to the inlet of the molten salt electric heater 20 through a low-temperature molten salt delivery pipe 27, and a low-temperature molten salt pump 28 is connected in series to the low-temperature molten salt delivery pipe 27;

[0028] When in use, the molten salt in the molten salt electric heater 20 can be heated by the molten salt electric heater 20 using the electric energy during the electricity off-peak period. The heated high-temperature molten salt is transported to the high-temperature molten salt storage tank 21 with the help of the power from the high-temperature molten salt pump 22 and stored for standby use. At the same time, the molten salt in the low-temperature molten salt storage tank 26 is transported to the molten salt electric heater 20 using the low-temperature molten salt pump 28 and the low-temperature molten salt delivery pipe 27. The low-temperature molten salt entering the molten salt electric heater 20 is heated by the electric energy during the electricity off-peak period.

[0029] The outlet of the heating channel of the evaporator 24 is connected to the inlet of the high-temperature steam pipeline 29, and the inlet of the heating channel of the evaporator 24 is connected to the outlet of the deoxygenated water delivery pipeline 30. The deoxygenated water delivery pipeline 30 is connected in series with a valve and a secondary pressurized water pump 31. The inlet of the deoxygenated water delivery pipeline 30 is connected to the water outlet of the deaerator 19. The water inlet of the deaerator 19 is connected to the water outlet of the hot water storage tank 6 through the hot water delivery pipe 18, and the hot water delivery pipe 18 is connected in series with a primary pressurized water pump 17.

[0030] When it is not necessary to output high-temperature steam to the outside during off-peak electricity consumption, the evaporator 24 can be used to produce high-temperature steam and deliver it to users. The specific method is to use the high-temperature molten salt stored in the high-temperature molten salt storage tank 21 to heat the hot water from the deaerator 19 through the evaporator 24. The molten salt after heat exchange will flow to the low-temperature molten salt storage tank 26, and will eventually circulate to the molten salt electric heater 20 to be heated, and then return to the high-temperature molten salt storage tank 21.

[0031] The carbon dioxide air source heat pump uses carbon dioxide (R744) as a refrigerant. It is an environmentally friendly refrigerant and a colorless and odorless gas at room temperature. The critical temperature and critical pressure of carbon dioxide (R744) are 31.1°C and 7.37MPa, respectively. As a refrigerant, carbon dioxide (R744) has many advantages over other refrigerants: its ozone depletion potential ODP = 0, and its global warming potential WMP = 1. It does not damage the ozone layer, does not require recycling and regeneration, and is an ideal natural refrigerant. The outlet water temperature of the carbon dioxide air source heat pump can reach 95°C, and it can operate normally at an ambient temperature of -35°C. It is a natural refrigerant and pollution-free, making it a veritable energy-saving and environmentally friendly product.

[0032] Existing carbon dioxide air source heat pump water heaters generally include six parts: carbon dioxide compressor, evaporator, condenser, throttle valve, regenerator and electronic control system. Low-temperature and low-pressure carbon dioxide liquid evaporates and absorbs heat in the evaporator, absorbing the heat of the external ambient air to become gaseous. The gaseous carbon dioxide enters the compressor after passing through the regenerator. Driven by the power of the power grid, the carbon dioxide is compressed by the compressor into high-temperature and high-pressure gaseous carbon dioxide, and then enters the condenser. During condensation, the carbon dioxide releases heat to water. The cooled carbon dioxide changes from gas to liquid, and then enters the regenerator to further release heat to the carbon dioxide gas coming out of the evaporator. After coming out of the regenerator, it is further reduced in pressure by the expansion valve to become a low-temperature and low-pressure liquid, and enters the evaporation again. Since carbon dioxide (critical temperature 31.1℃, critical pressure 7.37MPa) needs to change from a supercritical state to a liquid state in the heat pump cycle, its heat release process in the condenser is a large temperature difference heat release process, which is just suitable for heating cold water from room temperature to below boiling point. According to the current unit operating conditions at home and abroad, the water temperature usually does not exceed 95℃ after heating. According to the data provided by a domestic manufacturer (when the ambient temperature is 23℃, the inlet water temperature is 23℃, the outlet water temperature is 95℃, and the unit COP can reach 3.29; when the ambient temperature is 7℃, the inlet water temperature is 23℃, the outlet water temperature is 95℃, and the unit COP can reach 2.43), it can be seen that the carbon dioxide air source heat pump hot water unit is used to heat cold water to 95℃ once, has high energy efficiency, and has obvious energy-saving effects.

[0033] As a further improvement of the present invention, the above-mentioned high-temperature steam pipeline 29 is connected to the steam outlet of the electrode boiler 14 or the electric heater through a backup steam pipeline 15 with a valve in series, and the water inlet of the electrode boiler 14 or the electric heater is connected to the water outlet section of the secondary pressurized water pump 31 on the deoxygenated water delivery pipeline 30 through a water supply pipeline 13 with a valve in series.

[0034] The electrode boiler 14 or the electric heater uses the electricity during the off-peak period to heat the softened water to produce steam. The evaporator 24 of the molten salt energy storage system does not work during the off-peak period. The production of steam supplied to the outside during the off-peak period is completed by the electrode boiler 14 or the electric heater, and the heat energy generated by the molten salt electric heater 20 is stored for standby use.

[0035] As a further improvement of the present invention, the high-temperature steam pipeline 29 is connected to the water inlet of the deaerator 19 through a branch pipeline 16 with a valve in series.

[0036] As a further improvement of the present invention, the outlet of the high-temperature molten salt storage tank 21 is connected to the inlet of the heat dissipation channel of the evaporator 24 through a spare high-temperature molten salt pipeline 34 connected in series with a spare high-temperature molten salt pump 33, and the outlet of the low-temperature molten salt storage tank 26 is connected to the inlet of the molten salt electric heater 20 through a spare low-temperature molten salt delivery pipe 37 connected in series with a spare low-temperature molten salt pump 36.

[0037] During use, when the high-temperature molten salt pump 22 fails and needs maintenance, the spare high-temperature molten salt pump 33 can be activated to replace the high-temperature molten salt pump 22; when the low-temperature molten salt pump 28 fails and needs maintenance, the spare low-temperature molten salt pump 36 can be activated to replace the low-temperature molten salt pump 28.

[0038] As a further improvement of the present invention, the softened water pipe 3 is connected to the primary hot water pipe 5 via a bypass pipe 38 with a valve in series.

[0039] As a further improvement of the present invention, the outlet water temperature discharged from the outlet of the heating channel of the above-mentioned condenser 4 does not exceed 95°C, the temperature of the high-temperature part of the molten salt circulating in the secondary energy storage system is 400°C-425°C, the temperature of the low-temperature part of the molten salt is 200°C-230°C, and the molten salt filled in the molten salt electric heater 20, the high-temperature molten salt storage tank 21 and the low-temperature molten salt storage tank 26 is a ternary mixed nitrate.

[0040] As a further improvement of the present invention, the above-mentioned ternary mixed nitrate is composed of 53% by weight of KNO 3 , 40% by weight NaNO 3 and 7% by weight NaNO 3 constitute.

[0041] As a further improvement of the present invention, the electrode boiler 14 or the electric heater is turned on to produce steam during the low electricity consumption period, and the evaporator 24 does not produce steam during the low electricity consumption period.

[0042] Specific implementation cases

[0043] A chemical enterprise in Jiangsu consumes 720t of 1.3MPa saturated steam every day, averaging 30t / h. The steam used needs to be purchased from outside at a price of 260 yuan / t. The enterprise's off-peak electricity price is 0.26 yuan / kWh, the flat electricity price is 0.63 yuan / kWh, and the peak electricity price is 1.08 yuan / kWh.

[0044] The company uses the molten salt energy storage coupled with CO 2 The operating state parameters of the air source heat pump water heater cascade energy storage steam supply system are as follows: the hot water temperature in the first-level energy storage heat storage water storage tank 6 is 95°C. Assuming the external tap water temperature is 10°C, the water temperature rises to 95°C after being heated once by the carbon dioxide air source heat pump water heater, and the 95°C hot water is stored in the water storage tank 6. The carbon dioxide air source heat pump water heater operates during the 8-hour valley power period, and the volume of the water storage tank 6 can meet the daily water demand of the enterprise. Considering that the steam supply needs to be carried out for 24 hours, and the 8-hour valley power water heater is always running, the water storage tank 6 actually only needs to meet the water storage capacity for 16 hours, so the effective volume of the water storage tank 6 is 480m 3 .

[0045] The ternary mixed nitrate used in the secondary energy storage molten salt is composed of 53% by weight of KNO 3 , 40% by weight NaNO 3 and 7% by weight NaNO 3 The temperature of the high-temperature molten salt circulating in the secondary energy storage system is 400℃-425℃, and the temperature of the low-temperature molten salt is 200℃-230℃. The 95℃ hot water is pressurized to 0.6MPa by the first-level pressurized water pump 17 and sent to the deaerator 19. In the deaerator 19, the water is heated to a saturated state (0.6MPa) by 1.3MPa saturated steam. The 0.6MPa saturated water is pressurized to 1.3MPa by the second-level pressurized water pump 31 and enters the evaporator 24. In the evaporator 24, the water evaporates and absorbs the heat in the high-temperature molten salt to become 1.3MPa saturated steam. Most of the 1.3MPa saturated steam is delivered to heat users, and a small part is delivered to the deaerator 19.

[0046] In this embodiment, due to the use of a primary energy storage and heat storage system for energy storage, the amount of molten salt can be reduced by 896t compared to the direct use of molten salt energy storage. The efficiency of the molten salt energy storage system is calculated at 85%. According to the average energy efficiency of the carbon dioxide air source heat pump water heater of 3.5, the power consumption per ton of steam is about 814 kWh, and the steam energy cost is about 212 yuan / ton. The total electricity cost of 8640 hours of continuous steam supply and 2880 hours of valley electricity operation throughout the year is about 54.95 million yuan. Other costs are considered at 2 million yuan, and the total cost of steam for the whole year is 56.95 million yuan. The original plan purchases steam at a price of 260 yuan / ton, which requires 67.392 million yuan per year. Subtracting the two, it can be seen that the economic benefit brought by reducing the cost of steam production is 10.442 million yuan per year, thereby reducing a large amount of energy costs for the enterprise, and the reduction accounts for 15.5% of its total steam cost.

[0047] The molten salt energy storage coupled with CO 2 The air source heat pump water heater cascade energy storage steam supply system has the following beneficial effects:

[0048] 1. Generating steam through cascade energy storage heating reduces the amount of molten salt used in simple molten salt energy storage, while also reducing the volume of the molten salt tank, thereby reducing the initial investment of the system.

[0049] 2. Make full use of valley electricity and use CO 2 Air source heat pump water heater heating saves energy while further reducing the energy cost of steam.

[0050] 3. Using valley electricity cascade energy storage heating to provide steam for industrial enterprises solves the environmental problems of the existing technology of using gas boilers to supply steam, as well as the problem of excessive cost fluctuations due to unstable natural gas prices;

[0051] Fourth, enterprises use energy storage systems to directly generate steam, which reduces pipeline network investment, reduces energy loss of steam along the pipeline network, and saves energy compared to purchasing steam from outside;

[0052] 5. Making full use of valley electricity storage during low-peak electricity consumption is beneficial to shifting peak power into valley power and increasing the absorption of new energy electricity.

[0053] In summary, the technical solution of the present invention makes full use of the characteristics of water and molten salt media, adopts cascade energy storage heating technology to produce steam, and achieves the effect of energy saving and cost reduction to the greatest extent; at the same time, the technical solution of the present invention adopts CO 2 The air source heat pump water heater combines the hot water storage tank with the molten salt system for two-stage energy storage, which can save more than 9% of energy compared with the simple molten salt energy storage. 2The air source heat pump water heater cascade energy storage steam supply system has the advantages of making full use of the electricity price advantage during off-peak hours, has high energy efficiency, can minimize the operating costs of the enterprise's steam supply system, and provide the enterprise with lower-cost finished steam.

[0054] The embodiments described above are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary engineers and technicians in the field should all fall within the protection scope of the claims of the present invention.

Claims

1. Molten salt energy storage coupled with CO2 air source heat pump water heater cascade energy storage steam supply system, which is characterized by: The invention comprises a primary energy storage system and a secondary energy storage system, wherein the primary energy storage system comprises a softened water tank (1), wherein a water inlet of the softened water tank (1) is connected to a water outlet of a softened water treatment device (32) via a water delivery pipeline, wherein a water outlet of the softened water tank (1) is connected to a water inlet of a heat receiving channel of a condenser (4) of a carbon dioxide air source heat pump water heater via a softened water pipe (3) connected in series with a soft water pump (2), wherein a water outlet of the heat receiving channel of the condenser (4) is connected to a water inlet of a hot water storage tank (6) via a primary hot water pipe (5), and a high-temperature and high-pressure gaseous carbon dioxide inlet of a heat dissipation channel of the condenser (4) is connected to a hot water pipe (6) via a primary hot water pipe (5). The circulating medium channel is connected to the circulating medium outlet of the carbon dioxide compressor (7), the circulating medium inlet of the carbon dioxide compressor (7) is connected to the outlet of the heat receiving channel of the regenerator (9) through the high-temperature and low-pressure gaseous carbon dioxide pipeline (8), the inlet of the heat receiving channel of the regenerator (9) is connected to the medium outlet of the evaporator (10) through a pipeline, the medium inlet of the evaporator (10) is connected to the outlet of the heat dissipation channel of the regenerator (9) through a pipeline connected in series with an expansion valve (11), and the inlet of the heat dissipation channel of the regenerator (9) is connected to the outlet of the heat dissipation channel of the condenser (4) through a liquid carbon dioxide delivery pipeline (12); The secondary energy storage system comprises a molten salt electric heater (20), wherein the outlet of the molten salt electric heater (20) is connected to the inlet of a high-temperature molten salt storage tank (21) via a high-temperature molten salt delivery pipe (35), the outlet of the high-temperature molten salt storage tank (21) is connected to the inlet of a heat dissipation channel of an evaporator (24) via a high-temperature molten salt pipeline (23) connected in series with a high-temperature molten salt pump (22), the outlet of the heat dissipation channel of the evaporator (24) is connected to the inlet of a low-temperature molten salt storage tank (26) via a low-temperature molten salt pipeline (25), the outlet of the low-temperature molten salt storage tank (26) is connected to the inlet of the molten salt electric heater (20) via a low-temperature molten salt delivery pipe (27), and a low-temperature molten salt pump (28) is connected in series to the low-temperature molten salt delivery pipe (27); The outlet of the heating channel of the evaporator (24) is connected to the inlet of the high-temperature steam pipeline (29), the inlet of the heating channel of the evaporator (24) is connected to the outlet of the deoxygenated water delivery pipeline (30), a valve and a secondary pressurized water pump (31) are connected in series to the deoxygenated water delivery pipeline (30), the inlet of the deoxygenated water delivery pipeline (30) is connected to the water outlet of the deaerator (19), the water inlet of the deaerator (19) is connected to the water outlet of the hot water storage tank (6) through a hot water delivery pipe (18), and a primary pressurized water pump (17) is connected in series to the hot water delivery pipe (18).

2. The molten salt energy storage coupled CO2 air source heat pump water heater cascade energy storage steam supply system according to claim 1 is characterized in that: The high-temperature steam pipeline (29) is connected to the steam outlet of the electrode boiler (14) or the electric heater via a backup steam pipeline (15) connected in series with a valve, and the water inlet of the electrode boiler (14) or the electric heater is connected to the water outlet section of the secondary pressure water pump (31) on the deoxygenated water delivery pipeline (30) via a water replenishment pipeline (13) connected in series with a valve.

3. The molten salt energy storage coupled CO2 air source heat pump water heater cascade energy storage steam supply system according to claim 2 is characterized in that: The high-temperature steam pipeline (29) is connected to the water inlet of the deaerator (19) via a branch pipeline (16) connected in series with a valve.

4. The molten salt energy storage coupled CO2 air source heat pump water heater cascade energy storage steam supply system as claimed in claim 3 is characterized by: The outlet of the high-temperature molten salt storage tank (21) is connected to the inlet of the heat dissipation channel of the evaporator (24) through a spare high-temperature molten salt pipeline (34) connected in series with a spare high-temperature molten salt pump (33), and the outlet of the low-temperature molten salt storage tank (26) is connected to the inlet of the molten salt electric heater (20) through a spare low-temperature molten salt delivery pipe (37) connected in series with a spare low-temperature molten salt pump (36).

5. The molten salt energy storage coupled CO2 air source heat pump water heater cascade energy storage steam supply system according to claim 4 is characterized in that: The softening water pipe (3) is connected to the primary hot water pipe (5) via a bypass pipe (38) with a valve connected in series.

6. The molten salt energy storage coupled CO2 air source heat pump water heater cascade energy storage steam supply system according to any one of claims 1 to 5, characterized in that: The temperature of the water discharged from the outlet of the heat receiving channel of the condenser (4) does not exceed 95°C, the temperature of the high-temperature molten salt circulating in the secondary energy storage system is 400°C-425°C, and the temperature of the low-temperature molten salt is 200°C-230°C. The molten salt filled in the molten salt electric heater (20), the high-temperature molten salt storage tank (21) and the low-temperature molten salt storage tank (26) is a ternary mixed nitrate.

7. The molten salt energy storage coupled CO2 air source heat pump water heater cascade energy storage steam supply system according to claim 6 is characterized by: The ternary mixed nitrate is composed of 53% by weight of KNO3, 40% by weight of NaNO3 and 7% by weight of NaNO3.

8. The molten salt energy storage coupled CO2 air source heat pump water heater cascade energy storage steam supply system according to claim 7 is characterized in that: The electrode boiler (14) or the electric heater is turned on to produce steam during the low electricity consumption period, and the evaporator (24) does not produce steam during the low electricity consumption period.

9. The molten salt energy storage coupled CO2 air source heat pump water heater cascade energy storage steam supply system according to any one of claims 1 to 5, characterized in that: The electrode boiler (14) or the electric heater is turned on to produce steam during the low electricity consumption period, and the evaporator (24) does not produce steam during the low electricity consumption period.

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