Double-molten-salt heat storage Carnot battery of transcritical carbon dioxide heat pump coupling tower type loop

Abstract

The utility model relates to a double-fused-salt heat storage Carnot battery of a transcritical carbon dioxide heat pump coupling tower type loop, and belongs to the technical field of energy storage. Comprising a transcritical carbon dioxide heat pump loop, a molten salt loop and a water vapor Rankine cycle loop. The improvement lies in that a tower type solar heat collector loop with solar salt as a working medium is arranged in a coupling manner; the tower type solar heat collector loop comprises a solar salt side of a steam generator, a solar salt side of a superheater, a solar salt side of a heat regenerator, a first solar salt pump, a high-temperature solar salt tank, a solar heat collector, a solar salt side of a first coupling heat exchanger, a second solar salt pump and a low-temperature solar salt tank which are sequentially connected in series. The coupled tower type solar heat collector loop and the transcritical carbon dioxide heat pump loop jointly provide a heat source for Carnot battery power circulation, on one hand, larger heat can be provided, the system can bear larger-scale power circulation, and economic benefits are improved; on the other hand, heat loss is reduced through double heat sources, and system efficiency is improved.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the energy storage technology field, concretely relates to a novel heat storage Carnot battery which couples a transcritical carbon dioxide heat pump cycle loop and a tower heat collector cycle loop and uses two kinds of molten salt as a circulating working medium. BACKGROUND

[0002] The Carnot battery refers to a large-scale electric power energy storage system based on heat storage, is a novel electric energy storage technology, and can realize medium to large scale electric energy storage at low cost and without geographical restrictions. The Carnot battery converts electric energy into heat energy, stores the heat energy in a medium such as water or molten salt, and converts the heat energy into electric energy through a specific device when electric energy is needed.

[0003] Most conventional Carnot batteries use a single heat source in the form of only a heat pump cycle or only an electric heat exchanger. Due to the power limitation of the compressor, the heat pump cycle can only provide limited heat, thereby limiting the power generation scale of the power cycle. Therefore, in a system using a heat pump cycle as a heat source, an organic Rankine cycle is mostly selected as a power cycle, and the system efficiency is generally low. For a water vapor Rankine cycle, the working temperature is generally not high due to the limitation of the water evaporation temperature, and is generally about 310-337 DEG C, which greatly limits the round-trip efficiency of the Carnot battery system. The working medium of the organic Rankine cycle is limited to conventional refrigerants, hydrocarbons, and siloxanes, and the maximum operating temperature is only about 300 DEG C, and the efficiency is low. The steam Rankine cycle (SRC) is widely used in coal-fired power plants and nuclear power plants due to its high efficiency, energy saving, and environmental protection. The high-temperature and high-pressure steam enters the turbine to expand and do work, which can bring greater power generation efficiency.

[0004] The electric heat exchanger is a heat source form mostly selected by commercial Carnot battery demonstration projects at present, which can provide a large amount of heat and a higher heat source temperature. However, the electric heat exchanger has a low efficiency, and the maximum efficiency is about 0.95, which will lead to a continuous increase in heat loss as the heat supply power increases.

[0005] The prior art provides energy for the entire large-scale electric power energy storage system through a transcritical carbon dioxide heat pump. Since the compressor of the transcritical carbon dioxide heat pump has a low power, the heat provided is limited, thereby affecting the overall heat storage capacity of the transcritical Rankine cycle, the main steam parameters are not high, and the Carnot battery energy storage system of the prior art cannot fully exert the efficiency. UTILITY MODEL CONTENTS

[0006] In order to solve the problems of low maximum round-trip efficiency of conventional Carnot batteries, difficulty in adjusting the thermal cycle and the heat storage medium, and temperature mismatch, the utility model provides a double molten salt heat storage Carnot battery coupled with a transcritical carbon dioxide heat pump and a tower system.

[0007] The utility model discloses a new type of thermal storage Carnot cell that cross-critical carbon dioxide heat pump circulation loop and tower type heat collector circulation loop are coupled and two kinds of molten salt are used as circulating working medium.

[0008] The cross-critical carbon dioxide heat pump coupling tower type loop's double molten salt thermal storage Carnot cell includes cross-critical carbon dioxide heat pump loop, molten salt loop and subcritical water vapor Rankine circulation loop.

[0009] The working medium of cross-critical carbon dioxide heat pump loop is carbon dioxide, and cross-critical carbon dioxide heat pump loop includes the carbon dioxide side of first coupling heat exchanger 4, carbon dioxide turbine 6, carbon dioxide side of carbon dioxide evaporator 7 in series connection of first preheater 1, second preheater 2, carbon dioxide compressor 3, carbon dioxide side of second coupling heat exchanger 5.

[0010] The working medium of molten salt loop is molten salt, and molten salt loop includes the molten salt side of second coupling heat exchanger 5, second high-temperature molten salt tank 10, molten salt side of water preheater 12 in series connection of second low-temperature molten salt tank 8, first molten salt pump 9, second molten salt pump 11.

[0011] The working medium of subcritical water vapor Rankine circulation loop is water, and subcritical water vapor Rankine circulation loop includes the water side of first water pump 36, second water pump 30, open feed water heat exchanger 28, third heat exchanger 27, fourth heat exchanger 25, fifth heat exchanger 23, condenser 35's water side, high-pressure turbine 34, low-pressure turbine 21, water side of regenerator 15, water side of superheater 14, water side of steam generator 13 in series connection of first heat exchanger 33, second heat exchanger 31 and water preheater 12.

[0012] It further includes tower type solar heat collector loop, and the working medium of tower type solar heat collector loop is solar salt.

[0013] Tower type solar heat collector loop includes the solar salt side of first coupling heat exchanger 4, solar salt side of solar heat collector 18, low-temperature solar salt tank 20, second solar salt pump 19 and high-temperature solar salt tank 17 in series connection of steam generator 13's solar salt side, superheater 14's solar salt side, regenerator 15's solar salt side, first solar salt pump 16.

[0014] Further technical solutions are as follows:

[0015] Solar heat collector 18 is tower type solar heat collector.

[0016] Compared with prior art, the utility model has the beneficial technical effect in the following aspects:

[0017] 1. The utility model discloses a trans-critical carbon dioxide heat pump is coupled with tower heat collector for the first time and is applied to Carnot cell. Based on the above-mentioned defects, the utility model discloses for the first time that solar energy is introduced into auxiliary trans-critical carbon dioxide heat pump circulation and is used as heat source, and through coupling tower heat collector and trans-critical carbon dioxide heat pump circulation, heat is provided for Carnot cell power circulation. Through the double heat source form of heat pump and tower heat collector, on the one hand, greater heat can be provided, the system can undertake larger scale power circulation, and higher economic benefit is obtained. On the other hand, the use of double heat source in Carnot television can reduce heat loss, and higher system efficiency is obtained.

[0018] The original trans-critical carbon dioxide heat pump circuit is not changed, and a tower solar heat collector circuit is added to the heat supply circuit to provide heat to the subcritical Rankine cycle circuit. The heat storage capacity of the subcritical Rankine cycle circuit is increased, and the maximum round-trip efficiency of the system is changed from the original 66.27% to 278%.

[0019] 2. The utility model discloses a subcritical water vapor Rankine cycle as the power circulation form of Carnot cell, wherein the main steam parameter can reach 540 DEG C / 8.59MPa, and the maximum round-trip efficiency of the system reaches 278%. The round-trip efficiency of the system is the product of the heat pump COP, the heat storage efficiency and the power generation efficiency. In the utility model, the maximum heat pump COP is about 1.3, the maximum power generation efficiency is about 41%, but the maximum heat storage efficiency can reach about 500%. Higher heat storage efficiency is the main reason for higher round-trip efficiency. The heat storage efficiency is defined as the ratio of the heat absorption of the power cycle to the heat supply of the heat pump cycle, that is, the heat absorbed by the Rankine cycle divided by the heat provided by the heat pump cycle. In a single heat source system with only heat pump cycle, the maximum heat storage efficiency is 100%. In the utility model, solar energy is coupled with the heat pump cycle as double heat source, the heat absorbed by the Rankine cycle is provided by the heat pump cycle and solar energy, and as the heat provided by the solar tower gradually increases, the heat storage efficiency also continuously increases, and the maximum reaches 515.7%.

[0020] 3. The first time two different melting point of molten salt is used in the Carnot cell, namely two high temperature molten salt tank and two low temperature molten salt tank structure. The heat storage time of different molten salt tank can be flexibly adjusted according to the system heat storage requirement. The molten salt is used as the medium of medium-high temperature heat transfer and heat storage, which has the advantages of low pressure, wide liquid temperature range, good heat transfer performance, large heat storage density, low price and so on. Solar salt is used as the heat storage medium at high temperature end, which has high thermal stability, good economy and low vapor pressure, so it is the mainstream of heat storage at present. However, the high melting point of 221℃ limits its application in the field of medium and low temperature. In order to further store the medium and low temperature heat source and realize the cascade utilization of energy, ternary nitrite ternary molten salt (which is mixed by 15% sodium nitrate (NaNO3), 43% potassium nitrate (KNO3) and 42% calcium nitrate (Ca(NO3)2), which has low melting point, high decomposition temperature and excellent heat transfer and heat storage performance, can reduce the operation cost and the risk of freezing of the system. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is a system structure schematic diagram of the utility model;

[0022] Figure 2 It is a temperature-entropy (T-s) diagram of water vapor Rankine cycle and transcritical carbon dioxide heat pump circuit in the system of the utility model;

[0023] Figure 3 It is a temperature-enthalpy diagram of primary preheater, secondary preheater, first coupled heat exchanger and second coupled heat exchanger in the system of the utility model;

[0024] Figure 4 It is a flow chart of heat transfer in transcritical carbon dioxide heat pump circuit, tower type solar heat collector circuit and molten salt circulation circuit in the utility model.

[0025] Figure 1 The serial number: primary preheater 1, secondary preheater 2, carbon dioxide compressor 3, first coupled heat exchanger 4, second coupled heat exchanger 5, carbon dioxide turbine 6, carbon dioxide evaporator 7, second low temperature molten salt tank 8, first molten salt pump 9, second high temperature molten salt tank 10, second molten salt pump 11, water preheater 12, steam generator 13, superheater 14, regenerator 15, first solar salt pump 16, high temperature solar salt tank 17, solar heat collector 18, second solar salt pump 19, low temperature solar salt tank 20, low pressure turbine 21, first throttling valve 22, fifth heat exchanger 23, second throttling valve 24, fourth heat exchanger 25, third throttling valve 26, third heat exchanger 27, open feed water heat exchanger 28, fourth throttling valve 29, second water pump 30, second heat exchanger 31, fifth throttling valve 32, first heat exchanger 33, high pressure turbine 34, condenser 35, first water pump 36. DETAILED DESCRIPTION

[0026] The utility model will be further described by examples in combination with the drawings.

[0027] Embodiment

[0028] Referring to Figure 1 The double molten salt heat storage Carnot cell coupled with the transcritical carbon dioxide heat pump and the tower type circuit comprises a transcritical carbon dioxide heat pump circuit, a molten salt circuit and a subcritical water vapor Rankine cycle circuit.

[0029] The working medium of the transcritical carbon dioxide heat pump circuit is carbon dioxide, and the transcritical carbon dioxide heat pump circuit comprises, in series, a first preheater 1, a second preheater 2, a carbon dioxide compressor 3, a carbon dioxide side of a first coupling heat exchanger 4, a carbon dioxide side of a second coupling heat exchanger 5, a carbon dioxide turbine 6 and a carbon dioxide side of a carbon dioxide evaporator 7.

[0030] The working medium of the molten salt circuit is molten salt, and the molten salt circuit comprises, in series, a second low-temperature molten salt tank 8, a first molten salt pump 9, a molten salt side of the second coupling heat exchanger 5, a second high-temperature molten salt tank 10, a second molten salt pump 11 and a molten salt side of a water preheater 12.

[0031] The working medium of the subcritical water vapor Rankine cycle circuit is water, and the subcritical water vapor Rankine cycle circuit comprises, in series, a water side of the water preheater 12, a water side of a steam generator 13, a water side of a superheater 14, a water side of a regenerator 15, a low-pressure turbine 21, a high-pressure turbine 34, a water side of a condenser 35, a first water pump 36, a fifth heat exchanger 23, a fourth heat exchanger 25, a third heat exchanger 27, an open feed water heat exchanger 28, a second water pump 30, a second heat exchanger 31 and a first heat exchanger 33.

[0032] A first throttling valve 22 is connected in parallel between a high-temperature steam inlet of the fifth heat exchanger 23 and an outlet of the low-pressure turbine 21, a second throttling valve 24 is connected in parallel between a low-temperature water inlet of the fourth heat exchanger 25 and a low-temperature water outlet of the fifth heat exchanger 23, a third throttling valve 26 is connected in parallel between a low-temperature water inlet of the third heat exchanger 27 and a low-temperature water outlet of the fourth heat exchanger 25, a fourth throttling valve 29 is connected in parallel between a low-temperature water inlet of the second heat exchanger 31 and a low-temperature water outlet of the open feed water heat exchanger 28, and a fifth throttling valve 32 is connected in parallel between a low-temperature water inlet of the first heat exchanger 33 and a low-temperature water outlet of the second heat exchanger 31.

[0033] The utility model further comprises a tower type solar heat collector circuit, and the working medium of the tower type solar heat collector circuit is solar salt.

[0034] The tower type solar heat collector loop comprises, in series, a solar salt side of the steam generator 13, a solar salt side of the superheater 14, a solar salt side of the regenerator 15, the first solar salt pump 16, a high-temperature solar salt tank 17, a solar salt side of the solar heat collector 18, a solar salt side of the first coupled heat exchanger 4, the second solar salt pump 19 and a low-temperature solar salt tank 20.

[0035] The working principle of the utility model is explained in detail as follows:

[0036] Referring to Figure 2 , the low-temperature side of the carbon dioxide evaporator 7 is directly connected to the external environment and uses air as a heat source to provide heat for the entire carbon dioxide heat pump loop. The low-temperature side of the condenser 35 is connected to a cooling tower to remove condensation heat using air.

[0037] Table 1

[0038]

[0039]

[0040] In this embodiment, the temperature of the entire system is adjusted by adjusting the high-pressure turbine 34 inlet d point pressure of the water vapor Rankine cycle and the inlet temperature of the solar heat collector 18, and the highest efficiency point is obtained when the high-pressure turbine 34 inlet d point pressure is 8.59 MPa and the inlet temperature of the solar heat collector 18 is 365℃. At this time, the round-trip efficiency of the subcritical water vapor Rankine cycle loop is 278.53%, and the system efficiency is 41.34%. The thermodynamic parameters of each point at the maximum round-trip efficiency, including temperature, pressure, enthalpy, entropy and state, are shown in Table 1, and the temperature-entropy diagram corresponding to each state point is shown in Figure 2 Referring to Figure 3 , it can be seen that the state of the working medium in the first preheater 1, the second preheater 2, the first coupled heat exchanger 4 and the second coupled heat exchanger 5 changes. The state change of the substance in the first coupled heat exchanger 4 and the second coupled heat exchanger 5 respectively embodies the process of transferring heat from the transcritical carbon dioxide heat pump loop to the tower type solar heat collector loop and the transcritical carbon dioxide heat pump loop to the molten salt circulation loop. From the data in the figure, the amount of heat transferred between the three loops can be calculated. Referring to Figure 4 Under this condition, the transcritical carbon dioxide heat pump loop transfers 1.46 MW of heat to the ternary molten salt circulation loop and 22.86 MW of heat to the tower type solar heat collector loop. The parameters of each state point and the flow of the working medium under this working condition are described below.

[0041] In the left transcritical carbon dioxide heat pump circuit, the high-temperature and high-pressure carbon dioxide with a pressure of 20 MPa and a temperature of 570°C from the outlet v point of the carbon dioxide compressor 3 enters the first coupling heat exchanger 4 and the two-stage preheater 2 in turn to release heat to the low-temperature and low-pressure carbon dioxide working medium in the tower type solar heat collector circuit and the self circuit respectively. The carbon dioxide working medium at the outlet x point of the two-stage preheater 2 has a pressure of 20 MPa and a temperature of 318.8°C. The carbon dioxide working medium at the high-temperature side outlet of the two-stage preheater 2 continues to be divided into two routes: one route releases heat to the one-stage preheater 1 to become the state with a pressure of 20 MPa and a temperature of 33.1°C; and the other route releases heat to the second coupling heat exchanger 5 to become the state with a pressure of 20 MPa and a temperature of 277.5°C. The two routes of carbon dioxide working medium are combined, the pressure becomes 20 MPa, and the temperature becomes 86.5°C, and then the combined carbon dioxide working medium enters the carbon dioxide turbine 6 to do work further. The carbon dioxide working medium at the outlet r point of the carbon dioxide turbine 6 has a pressure of 4.50 MPa and a temperature of 10°C, and enters the carbon dioxide evaporator 7 to absorb heat. The pressure and the temperature of the carbon dioxide working medium at the outlet s point of the carbon dioxide evaporator 7 remain unchanged, but the enthalpy value is increased. The low-temperature and low-pressure carbon dioxide working medium absorbs heat in the one-stage preheater 1, the two-stage preheater 2 and the carbon dioxide compressor 3 in turn, and becomes the high-temperature and high-pressure carbon dioxide working medium again, which has a pressure of 20 MPa and a temperature of 570°C.

[0042] The circulating working medium of the tower type solar heat collector circuit is solar salt, which is composed of 40% potassium nitrate and 60% sodium nitrate. The melting point of the solar salt is 220°C, and the maximum working temperature can reach 600°C. The solar salt working medium with the temperature of 560°C after absorbing heat in the solar heat collector 18 enters the first high-temperature molten salt tank 17, and the liquid solar salt is pumped into two circuits by the first solar salt pump 16: one route enters the regenerator 15 to reheat the steam at the end of the high-pressure turbine 34, and the temperature of the molten salt at the outlet of the regenerator 15 becomes 350.75°C; and the other route enters the superheater 14 and the steam generator 13 in turn to heat the unsaturated steam in the subcritical water vapor Rankine cycle circuit to the superheated state. The temperature of the solar salt working medium at the outlet n point of the superheater 14 is 473.59°C, and the temperature at the outlet o point of the steam generator is 310°C. The temperatures of the two routes of solar salt working medium are combined, and the temperature at the m point becomes 318.03°C, and then the combined solar salt working medium enters the low-pressure molten salt tank 20 and is pumped into the first coupling heat exchanger 4 by the second solar salt pump 19 to absorb heat transferred from the transcritical carbon dioxide heat pump circuit. At this time, the temperature of the solar salt working medium is increased to 365°C at the outlet of the coupling heat exchanger molten salt side. Then the solar salt working medium enters the solar heat collector 18 to absorb heat and complete the circulation of the whole circuit.

[0043] The working fluid of the molten salt cycle loop is ternary molten salt, which is composed of 15% sodium nitrate (NaNO3), 43% potassium nitrate (KNO3) and 42% calcium nitrate (Ca(NO3)2). It is a kind of molten salt working fluid widely used in solar thermal power generation system. The main function of the molten salt cycle loop is to transfer part of the heat of the transcritical carbon dioxide heat pump cycle to the subcritical water vapor Rankine cycle, providing heat for the water working fluid in the water preheater 12. The ternary molten salt heated by the second coupling heat exchanger 5 enters the second high-temperature molten salt tank 10, and then is pumped into the molten salt end inlet p of the water preheater 12 by the second molten salt pump 11, at this time the temperature is 309.83℃. In the water preheater 12, heat is provided to the subcritical water vapor Rankine cycle, and the temperature of the molten salt end outlet q of the water preheater 12 decreases to 266.48℃. The ternary molten salt working fluid that has released all the heat passes through the low-temperature molten salt tank 8 and the first molten salt pump 9 in turn. Then it enters the molten salt end of the second coupling heat exchanger 5 and is heated to a state with a temperature of 309.83℃ to complete the entire cycle.

[0044] The working fluid of the subcritical water Rankine cycle loop is water, which is heated by the tower solar collector loop and the molten salt loop. The water at the outlet a' of the first heat exchanger 33 is liquid water at a temperature of 256.48°C and a pressure of 8.59 MPa, which enters the water preheater 12 to absorb heat from the molten salt loop. At the outlet b of the water preheater, the water is at a temperature of 300°C and a pressure of 8.59 MPa. The water then enters the steam generator 13 to absorb heat from the tower solar collector loop, and the temperature and pressure remain unchanged, but the state of the water changes from liquid water to saturated steam. The saturated steam then enters the superheater 14 to further absorb heat, and at the outlet d of the superheater, the steam is at a temperature of 540°C and a pressure of 8.59 MPa. The superheated steam then enters the high-pressure turbine 34, which has two-stage extraction function. The first-stage extraction steam flows to the first heat exchanger 33, and at the inlet e of the first heat exchanger, the steam is at a temperature of 444.64°C and a pressure of 4.54 MPa. The second-stage extraction steam is divided into two parts, which flow to the regenerator 15 and the second heat exchanger 31, respectively. The steam at the inlet of the regenerator 15 is at a temperature of 340.75°C and a pressure of 2.06 MPa, and it absorbs heat from the tower solar collector loop in the regenerator 15. At the outlet g of the regenerator, the steam is at a temperature of 540°C and a pressure of 8.59 MPa, and it enters the low-pressure turbine 21. The steam at the inlet of the second heat exchanger 31 heats the liquid water in the loop, and at the inlet of the fourth throttle valve 29, the steam is at a temperature of 179.33°C and a pressure of 2.00 MPa. The remaining steam from the high-pressure turbine 34 and the steam from the regenerator 15 enter the low-pressure turbine 21 to charge the Carnot cell. The low-pressure turbine 21 has four-stage extraction function. The first-stage extraction steam heats the liquid water in the open feedwater heat exchanger 28, and at the outlet h of the first-stage extraction, the steam is at a temperature of 414.48°C and a pressure of 0.88 MPa. The second-stage extraction steam also heats the liquid water in the open feedwater heat exchanger 28, and at the outlet i of the second-stage extraction, the steam is at a temperature of 302.26°C and a pressure of 0.36 MPa. The steam then enters the fourth heat exchanger 25 through the third throttle valve 26.The third stage extraction steam is extracted to the open feedwater heater 28 to heat the liquid water, and the temperature of the steam from the third stage extraction j is 185.95℃, and the pressure is 0.12MPa. After the heat transfer, the steam enters the fifth heat exchanger 23 through the second throttle valve 24. The fourth stage extraction steam is extracted to the open feedwater heater 28 to heat the liquid water, and the temperature of the steam from the fourth stage extraction k is 77.99℃, and the pressure is 0.03MPa. After the heat transfer, the steam enters the main path before the condenser 35 inlet through the fifth throttle valve 22. The remaining steam in the low pressure turbine 21 is in the state of temperature 41.51℃ and pressure 0.008MPa when it is discharged from the tail low pressure turbine 21. After the steam from the fifth throttle valve is combined, it enters the condenser inlet l and is condensed into liquid water, and the state is temperature 41.51℃ and pressure 0.008MPa. The water from the condenser 35 outlet a is heated to the liquid water of temperature 256.48℃ and pressure 8.59MPa by the fifth heat exchanger 23, the fourth heat exchanger 25, the third heat exchanger 27, the open feedwater heater 28, the second heat exchanger 31 and the first heat exchanger 33 in turn. The heated liquid water enters the water preheater 12 through the inlet to absorb the heat transferred from the molten salt circuit, and completes the whole cycle.

Claims

1. A double molten salt thermal storage Carnot cell coupled with a transcritical carbon dioxide heat pump tower circuit, comprising a transcritical carbon dioxide heat pump circuit, a molten salt circuit and a subcritical water vapor Rankine cycle circuit; the working medium of the transcritical carbon dioxide heat pump circuit is carbon dioxide, and the transcritical carbon dioxide heat pump circuit comprises, in series, a first preheater (1), a second preheater (2), a carbon dioxide compressor (3), a carbon dioxide side of a first coupling heat exchanger (4), a carbon dioxide side of a second coupling heat exchanger (5), a carbon dioxide turbine (6), and a carbon dioxide side of a carbon dioxide evaporator (7); the working medium of the molten salt circuit is molten salt, and the molten salt circuit comprises, in series, a second low-temperature molten salt tank (8), a first molten salt pump (9), a molten salt side of the second coupling heat exchanger (5), a second high-temperature molten salt tank (10), a second molten salt pump (11), and a molten salt side of a water preheater (12); the working medium of the subcritical water vapor Rankine cycle circuit is water, and the subcritical water vapor Rankine cycle circuit comprises, in series, a water side of the water preheater (12), a water side of a steam generator (13), a water side of a superheater (14), a water side of a regenerator (15), a low-pressure turbine (21), a high-pressure turbine (34), a water side of a condenser (35), a first water pump (36), a fifth heat exchanger (23), a fourth heat exchanger (25), a third heat exchanger (27), an open feedwater heat exchanger (28), a second water pump (30), a second heat exchanger (31), and a first heat exchanger (33); characterized in that further comprising a tower solar collector circuit, and the working medium of the tower solar collector circuit is solar salt; the tower solar collector circuit comprises, in series, a solar salt side of the steam generator (13), a solar salt side of the superheater (14), a solar salt side of the regenerator (15), a first solar salt pump (16), a high-temperature solar salt tank (17), a solar salt side of a solar collector (18), a solar salt side of the first coupling heat exchanger (4), a second solar salt pump (19), and a low-temperature solar salt tank (20).

2. The double molten salt thermal regenerative Carnot cell coupled to a transcritical carbon dioxide heat pump cascade circuit according to claim 1, characterized in that: the solar collector (18) is a tower solar collector.

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