CN110118160B - Solar supercritical carbon dioxide Brayton cycle system - Google Patents

Abstract

The invention discloses a solar supercritical carbon dioxide Brayton cycle system, comprising a solar heat absorber, a turbine unit and a Brayton cycle unit, wherein the solar heat absorber and the Brayton cycle unit are respectively connected with the turbine unit through pipelines; and Including a storage tank in parallel or in series with the pipeline between the solar heat absorber and the turbine unit for storing metal carbonates and metal oxides; for the storage of supercritical carbon dioxide. The solar supercritical carbon dioxide Brayton cycle system provided by the invention couples the direct production of supercritical carbon dioxide based on thermochemistry with the supercritical carbon dioxide Brayton cycle, which can realize high-efficiency energy storage and heat exchange, improve device efficiency, and reduce costs.

Description

Solar supercritical carbon dioxide Brayton cycle system

technical field

The invention relates to the technical field of energy, in particular to a solar supercritical carbon dioxide Brayton cycle system.

Background technique

The annual solar radiation received by my country's land surface is equivalent to 4.9 trillion tons of standard coal. The western Qinghai-Tibet Plateau, the back of Gansu, northern Ningxia, and southern Xinjiang are the regions with the most abundant solar energy resources, with a development potential of more than 85 trillion kWh/year. Accounting for about 75% of the country's total, my country's solar energy contains huge potential for development. Solar power generation technology is mainly divided into two categories: photovoltaic power generation and solar thermal power generation. Photovoltaic power generation has many disadvantages, such as discontinuous day and night, high energy storage cost, serious solar abandonment and short service life. Solar thermal power generation can use cheap energy storage technology to stabilize the output of power generation, which can be used as both basic load power supply and peak-shaving power supply. Therefore, solar thermal power generation has great potential in the future. Solar thermal power generation technologies include tower, tank The basic principle of solar thermal power generation is to form energy with high heat flux density through the concentrating paraboloid, and heat the work medium to drive the heat engine to generate electricity.

Solar supercritical carbon dioxide Brayton cycle uses solar energy as heat source and carbon dioxide in supercritical state (critical pressure 7.38MPa, critical temperature 30.98℃) as working fluid to realize energy conversion. Compared with the water vapor Rankine cycle, the supercritical carbon dioxide Brayton cycle performs work in a single phase, the system design is simple, and the complexity of the operation is reduced; the density is large, the compression work is small, and the heat exchange performance is good, which can reduce the turbine and heat exchanger. volume, so as to achieve the purpose of reducing costs and improving overall efficiency. In addition, supercritical carbon dioxide is non-toxic, harmless, less corrosive, cheap, and uses concentrated solar energy (temperature range 550°C-800°C) as a heat source, with good thermal stability.

Energy storage technology can be divided into sensible heat energy storage, latent heat energy storage and thermochemical energy storage according to the energy storage method. Sensible heat energy storage is to store thermal energy through temperature increase without changing the material form, and the energy storage density is low. Latent heat energy storage stores thermal energy in the form of phase change, and phase change heat storage needs to absorb more heat, so the density of latent heat energy storage is higher than that of sensible heat energy storage. Compared with the above two heat storage methods, chemical energy heat storage has the advantages of high energy storage density, high energy storage temperature, long energy storage period, small heat loss, and is suitable for long-distance transportation.

CSP technology has been developed for decades, and it is currently at the commercial application level of the second-generation technology represented by molten salt. Due to the influence of high temperature corrosion, the average operating temperature of molten salt in the market is 565 °C, which is extremely Limits the overall efficiency of the solar supercritical CO2 Brayton cycle. At the same time, the insufficiency of energy storage and heat exchange technology combined with solar supercritical carbon dioxide is also another problem. Most of the heat storage medium and work medium use indirect heat exchange, and the heat exchange efficiency is low, which limits the improvement of the overall efficiency. In addition, in the supercritical carbon dioxide Brayton cycle system, the supplementary supercritical carbon dioxide device is complicated and the steps are cumbersome, and the device needs to be further simplified.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve the problems of low thermal efficiency and high cost of the existing solar supercritical carbon dioxide Brayton cycle system, and to provide a solar supercritical system that can realize high-efficiency energy storage and heat exchange, improve system efficiency and reduce costs. Critical carbon dioxide Brayton cycle system.

The object of the present invention is achieved through the following technical solutions:

The invention provides a solar supercritical carbon dioxide Brayton cycle system in which supercritical carbon dioxide circulates, and the system includes:

a solar heat absorber, a turbine unit and a Brayton cycle unit, the solar heat absorber and the Brayton cycle unit are respectively connected with the turbine unit through pipelines;

Also includes storage tanks connected in parallel or in series with the piping between the solar heat absorber and the turbine unit for storing metal carbonates and metal oxides;

A gas storage tank is also provided in the Brayton cycle unit for storing supercritical carbon dioxide;

When the light conditions are sufficient, the circulating supercritical carbon dioxide absorbs heat in the solar heat absorber; at the same time, the heat transfer medium absorbs heat in the solar heat absorber and transfers it to the metal carbonate in the storage tank, and the metal carbonate is decomposed React, store heat, generate supercritical carbon dioxide, and enter the turbine unit together with the circulating supercritical carbon dioxide to do external work; the supercritical carbon dioxide after the work passes through the Brayton cycle unit, part of it is stored in the gas storage tank, and the other part is returned to the solar heat absorber Absorb heat and cycle to do work;

When the light conditions are poor or there is no light, the solar heat absorber is isolated, and the supercritical carbon dioxide stored in the gas storage tank and the circulating supercritical carbon dioxide pass through the Brayton cycle unit together, enter the storage tank, and undergo a compound reaction with metal oxides. , release heat, heat supercritical carbon dioxide, and enter the turbine unit to do external work.

Among them, the Brayton cycle unit can be in various forms, such as a simple Brayton cycle unit, a recompression Brayton cycle unit, a recompression partial cooling Brayton cycle unit or a recompression intermediate cooling Brayton cycle unit.

Preferably, the Brayton cycle unit includes: a high temperature regenerator, a low temperature regenerator, a main compressor, a recompressor and a cooler; the supercritical carbon dioxide after the turbine unit performs external work passes through the high temperature regenerator and the low temperature regenerator After that, it is divided into two strands, one is cooled by the cooler, pressurized by the main compressor and heated by the low temperature regenerator, and then enters the high temperature regenerator together with the other strand of supercritical carbon dioxide which is pressurized by the recompressor, and then heated by the high temperature regenerator. After entering the solar heat absorber to absorb heat, the cycle does work. The above-mentioned Brayton cycle unit is a form of the recompression Brayton cycle. Two-stage regenerators and compressors are arranged in the Brayton cycle unit, which avoids the pinch point temperature and improves the heat recovery efficiency.

Preferably, the gas storage tank is arranged between the low temperature regenerator and the cooler. There are many options for the location of the gas storage tank. In order to reduce the cost of the gas storage tank, it is the best choice to store supercritical carbon dioxide at low temperature and low pressure. more suitable location.

Preferably, the turbine unit can be set as an intermediate reheating structure: the turbine unit includes a low-pressure turbine, a high-pressure turbine, and a solar thermal storage tank disposed between the low-pressure turbine and the high-pressure turbine, and the solar thermal storage tank is used to store solar heat; The supercritical carbon dioxide of the turbine unit first enters the high-pressure turbine to do external work, then absorbs heat in the solar heat storage tank, and then enters the low-pressure turbine to do external work.

Preferably, the heat absorption medium in the solar heat absorber is supercritical carbon dioxide, and the supercritical carbon dioxide is both a heat transfer medium and a work medium. After supercritical carbon dioxide absorbs solar heat in the solar heat absorber, it transfers the heat energy to the metal carbonate in the storage tank as a heat transfer medium, so that the flowing medium in the system only includes supercritical carbon dioxide, which acts as a heat absorption medium and The working medium avoids multiple intermediate heat exchange processes, reduces heat loss, simplifies the system, and improves system efficiency and economic benefits.

Preferably, the concentrating system of the solar heat absorber includes one or more of a tower concentrating system, a dish concentrating system, a trough concentrating system or a linear Fresnel concentrating system.

Preferably, the storage tank includes a fixed bed, a bubbling bed, a fluidized bed, a porous medium or a honeycomb ceramic, wherein the fluidized bed can be a circulating fluidized bed or an internal circulating fluidized bed or the like. The storage tank is both a storage place for metal carbonates/metal oxides and a generator for thermal storage and exothermic chemical reactions.

Further, preferably, when the storage tank is a porous medium or a honeycomb ceramic, the metal oxide or silicon carbide is used as the matrix, and the metal carbonate is supported on the surface of the porous medium or the honeycomb structure. Porous media or honeycomb ceramic storage tanks allow for a combination of sensible and thermochemical heat storage.

Preferably, the metal carbonates include one or more of carbonates of lithium, sodium, potassium, rubidium, cesium, francium, beryllium, magnesium, calcium, strontium, barium or radium, or include lithium, sodium, Multicomponent mixtures modified with carbonates of potassium, rubidium, cesium, francium, beryllium, magnesium, calcium, strontium, barium or radium, eg binary mixtures _{of MgCO3} and _Al2O3 .

With respect to the prior art, the system based on thermochemical direct production of supercritical carbon dioxide and supercritical carbon dioxide Brayton cycle coupling provided by the present invention has the following technical effects:

损，简化装置，提高了该系统的运行温度，从而提高了系统效率和经济效益。1. In the solar supercritical carbon dioxide Brayton cycle system provided by the present invention, the supercritical carbon dioxide that circulates work is directly heated by the solar heat absorber with solar heat, and the supercritical carbon dioxide is simultaneously used as a heat-absorbing medium and a work medium, avoiding the heat exchange

It reduces the damage, simplifies the device, and increases the operating temperature of the system, thereby improving the system efficiency and economic benefits.

2. When operating the solar supercritical carbon dioxide Brayton cycle system provided by the present invention, in the heat storage process, the metal carbonate of the energy storage material is decomposed, and at the same time of heat storage, supercritical carbon dioxide can be directly generated, not only can be used as a supercritical carbon dioxide. A supplementary source of carbon dioxide, which simplifies the device and can increase the work capacity.

3. When operating the solar supercritical carbon dioxide Brayton cycle system provided by the present invention, in the exothermic process, the metal oxide and the supercritical carbon dioxide are in direct contact, and a compound reaction occurs, and the heat can be directly transferred to the supercritical carbon dioxide, which improves the performance of the supercritical carbon dioxide. heat transfer efficiency.

Description of drawings

Fig. 1 is the schematic diagram of the solar supercritical carbon dioxide Brayton cycle system of the first embodiment of the present invention;

Fig. 2 is the schematic diagram of the solar supercritical carbon dioxide Brayton cycle system of the second embodiment of the present invention;

3 and 4 are schematic diagrams of a solar supercritical carbon dioxide Brayton cycle system according to a third embodiment of the present invention, wherein the system of FIG. 3 includes a recompression partial cooling Brayton cycle unit, and the system of FIG. 4 includes a recompression intermediate cooling Brayton frame cycle unit;

5 is a schematic diagram of a solar supercritical carbon dioxide Brayton cycle system according to a fourth embodiment of the present invention;

Fig. 6 is the schematic diagram of the storage tank of the fifth embodiment of the present invention;

7 is a schematic diagram of a storage tank according to a sixth embodiment of the present invention;

8 is a schematic diagram of a storage tank according to a seventh embodiment of the present invention;

9 is a schematic diagram of a solar heat absorber according to an eighth embodiment of the present invention;

10 is a schematic diagram of a solar heat absorber according to a ninth embodiment of the present invention;

11 is a schematic diagram of a solar supercritical carbon dioxide Brayton cycle system according to a ninth embodiment of the present invention.

Description of reference numbers:

1-solar heat absorber; 2-first valve; 3-turbine unit; 4-recompressor; 5-cooler; 6-main compressor; 7-second valve; 8-air tank; 9-th Three valves; 10-low temperature regenerator; 11-high temperature regenerator; 12-fourth valve; 13-storage tank; 14-fifth valve; 15-sixth valve; 16-pre-compressor; 17-intermediate cooling 18-fan; 31-low pressure turbine; 32-high pressure turbine; 33-solar heat storage tank; 61-baffle plate; 62-filter device.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings.

As shown in FIG. 1 , the first embodiment of the present invention relates to a solar supercritical carbon dioxide Brayton cycle system based on MgCO ₃ /MgO energy storage, in which supercritical carbon dioxide circulates, and the system includes:

The solar heat absorber 1, the turbine unit 3 and the Brayton cycle unit, the solar heat absorber 1 and the Brayton cycle unit are respectively connected with the turbine unit 3 through pipelines, and are used to store metal carbonates and corresponding metal oxide storage tanks 13 is connected in parallel with the circulating supercritical carbon dioxide pipeline between the solar heat absorber 1 and the turbine unit 3, and the gas storage tank 8 for storing the supercritical carbon dioxide is arranged in the Brayton cycle unit;

The Brayton cycle unit in this embodiment is a recompression Brayton cycle unit, which includes: a high temperature regenerator 11, a low temperature regenerator 10, a main compressor 6, a recompressor 4 and a cooler 5; high temperature regenerator The hot end of the regenerator 11 is connected to the turbine unit 3 and the low temperature regenerator 10, the cold end inlet of the high temperature regenerator 11 is connected to the recompressor 4 and the low temperature regenerator 10, and the cold end outlet of the high temperature regenerator 11 is connected to the solar heat absorption The hot end inlet of the low temperature regenerator 10 is connected to the high temperature regenerator 11, the hot end outlet of the low temperature regenerator 10 is connected to the recompressor 4 and the cooler 5, and the cold end of the low temperature regenerator 10 is connected to the main compressor. 6 and the high temperature regenerator 11 ; the cooler 5 is connected to the low temperature regenerator 10 and the main compressor 6 ;

The operation process of the solar supercritical carbon dioxide Brayton cycle system of this embodiment is as follows:

When the light conditions are sufficient, open the first valve 2, the fifth valve 14 and the third valve 9 of the gas storage tank 8 for air intake, which are arranged in the pipeline for circulating supercritical carbon dioxide, and close the The second valve 7 of the gas outlet and the fourth valve 12 leading to the storage tank 13, the circulating supercritical carbon dioxide absorbs heat in the solar heat absorber 1 and is heated to 750°C; at the same time, the solar heat is transferred to the storage tank through the heat exchange medium. When the MgCO ₃ in the tank 13 is 25MPa and the temperature reaches 669°C, the MgCO ₃ undergoes a decomposition reaction, and the heat is stored, and the supercritical carbon dioxide produced by the thermochemical and the circulating supercritical carbon dioxide through the solar heat absorber 1 enters the turbine unit 3 together , do external work.

After the low-pressure medium-temperature supercritical carbon dioxide after the work passes through the high-temperature regenerator 11 and the low-temperature regenerator 10, an equal amount of thermochemically generated supercritical carbon dioxide is stored in the gas storage tank 8, and the remaining supercritical carbon dioxide is divided into two strands. , one passes through the cooler 5, enters the main compressor 6, then passes through the low-temperature regenerator 10 for heating, merges with the other supercritical carbon dioxide passing through the re-compressor 4, and passes through the high-temperature regenerator 11 for heating, and finally enters the solar energy The heat absorber 1 absorbs heat to form high-temperature and high-pressure supercritical carbon dioxide, and continues to cycle to do work.

The chemical reaction that takes place in the above endothermic process is shown in the following equation, and thermal energy is stored in the form of chemical energy.

MgCO ₃ →MgO+CO ₂

When the light conditions are poor or there is no light, the fourth valve 12 , the first valve 2 and the fifth valve 14 are closed to isolate the solar heat absorber 1 . Open the second valve 7 of the gas storage tank 8 for gas outlet, close the third valve 9 for intake air, the thermochemically generated supercritical carbon dioxide stored in the gas storage tank 8 and the circulating supercritical carbon dioxide merge into a stream , and then divided into two parts, one is cooled by cooler 5, pressurized by main compressor 6, heated by low temperature regenerator 10, and then enters storage tank 13 together with another supercritical carbon dioxide pressurized by recompressor 4. , contact with MgO, a chemical reaction occurs, heat is released, the circulating supercritical carbon dioxide is heated to 700 ° C, and enters the turbine unit 3 to do external work.

The chemical reaction that occurs during the above exothermic process is represented by the following equation:

MgO+CO ₂ →MgCO ₃

The second embodiment of the present invention also relates to a solar supercritical carbon dioxide Brayton cycle system based on MgCO ₃ /MgO energy storage, the structure of which is shown in FIG. 2 .

The difference from the first embodiment is that the turbine unit 3 in this embodiment includes a low-pressure turbine 31, a high-pressure turbine 32, and a solar heat storage tank 33 disposed between the low-pressure turbine 31 and the high-pressure turbine 32 for storing solar heat , and the sixth valve 15 of the solar storage tank 33 for air intake. When the light conditions are sufficient, open the sixth valve 15, extract part of the high-temperature supercritical carbon dioxide heated by the solar heat absorber 1, enter the solar heat storage tank, release heat, and transfer the heat in the form of sensible heat, latent heat or thermochemical in the solar energy The heat storage tank 33 is stored, and the low-temperature supercritical carbon dioxide after releasing heat enters the circulation loop to complete the heat storage process of the solar heat storage tank 33 .

The difference between the operation process of the solar supercritical carbon dioxide Brayton cycle system of this embodiment and the first embodiment is that the supercritical carbon dioxide entering the turbine unit 3 first enters the high-pressure turbine 32 to perform external work, and then enters the solar heat storage tank 33 to perform external work. The heat is absorbed, and then enters the low-pressure turbine 31 to do external work, thereby improving the overall efficiency.

The third embodiment of the present invention also relates to a solar supercritical carbon dioxide Brayton cycle system based on MgCO ₃ /MgO energy storage, and differs from the second embodiment in that the Brayton cycle unit adds an intercooler 17, according to the intercooling The position of the device 17 is different, and its structure is shown in FIG. 3 or FIG. 4 .

The system shown in FIG. 3 includes a recompression part cooling Brayton cycle unit. The difference from the second embodiment is that a pre-compressor 16 and an intercooler 17 are added in this embodiment, and the pre-compressor 16 is located in the Before the main compressor 6 and the re-compressor 4, the intercooler 17 is located between the pre-compressor 16 and the main compressor 6, and the supercritical carbon dioxide cooled by the cooler 5 enters the pre-compressor 16 for pressurization and is divided into two parts. One is cooled by the intercooler 17, the main compressor 6 is pressurized, and the low-temperature regenerator 10 is heated, mixed with another supercritical carbon dioxide pressurized by the recompressor 4, and enters the high-temperature regenerator 11.

What is included in the system shown in FIG. 4 is the recompression intercooling Brayton cycle unit, which is different from the second embodiment in that a precompressor 16 and an intercooler 17 are added in this embodiment, and the precompressor 16 is located in the After cooler 5 and before intercooler 17 , intercooler 17 is located between pre-compressor 16 and main compressor 6 . The supercritical carbon dioxide flowing out from the low temperature regenerator 10 is divided into two streams, one is precooled by the cooler 5, the precompressor 16 is pressurized, the intercooler 17 is cooled, the main compressor 6 is pressurized, and the low temperature regenerator 10 is heated and mixed with another supercritical carbon dioxide that has been pressurized by the recompressor 4 to enter the high temperature regenerator 11 together.

The difference between the recompression part cooling Brayton unit and the recompression intercooling Brayton unit in this embodiment and the second embodiment is that the pre-compressor 16 and the intercooler 17 are added, which reduces the pressure ratio change. Sensitivity and compressor power consumption improves overall efficiency and is more suitable for larger turbine pressure ratio systems.

The fourth embodiment of the present invention also relates to a solar supercritical carbon dioxide Brayton cycle system based on MgCO ₃ /MgO energy storage, the structure of which is shown in FIG. 5 .

The difference from the first embodiment is that the storage tank 13 in this embodiment is connected in series with the circulating supercritical carbon dioxide pipeline between the solar heat absorber 1 and the turbine unit 3 .

The fifth embodiment of the present invention relates to the structure of the storage tank in the first to fourth embodiments. As shown in FIG. 6 , the storage tank in this embodiment has a fixed bed structure, which is simple in structure and free from particle wear.

The sixth embodiment of the present invention also relates to the structure of the storage tank in the first to fourth embodiments. As shown in FIG. 7 , the storage tank in this embodiment is a clapboard-type inner circulating fluidized bed structure, and a clapboard 61 and a filter device 62 are arranged in the circulating fluidized bed structure, and the use of the circulating fluidized bed can enhance heat transfer Mass transfer effect, thereby enhancing the reaction rate and ensuring the complete chemical reaction.

The seventh embodiment of the present invention also relates to the structure of the storage tank in the first to fourth embodiments. As shown in FIG. 8 , the storage tank in this embodiment has a honeycomb structure or a porous structure, with metal oxide or silicon carbide as the matrix, and MgCO ₃ is loaded on the surface of the honeycomb structure or porous structure. This structure can realize thermochemical and Solar energy is stored in the form of sensible heat.

The eighth embodiment of the present invention relates to the structure of the solar heat absorber in the first to fourth embodiments. As shown in FIG. 9 , the solar heat absorber in this embodiment is a spiral-tube cavity heat absorber. This structure can increase the temperature of supercritical carbon dioxide at the outlet of the solar heat absorber by increasing the length of the heating pipeline.

The ninth embodiment of the present invention relates to another structure of a solar heat sink suitable for use in the system of the present invention and a corresponding solar supercritical carbon dioxide Brayton cycle system.

The structure of the solar heat absorber in this embodiment is shown in FIG. 10 . This kind of solar heat absorber is a buried tube type particle fluidized bed heat absorber. The solar heat absorber is filled with appropriate particles, and carbon dioxide or other gases are used as the The fluidizing gas makes the solid particles in the solar heat absorber in a fluidized state, the solid particles absorb solar energy, and the heat is mainly transferred to the pipeline by convection and heat conduction, thereby heating the supercritical carbon dioxide in the pipeline. This heating method makes the temperature The distribution is more uniform, reducing the thermal stress of the pipeline.

The solar supercritical carbon dioxide Brayton cycle system corresponding to the buried-tube particle fluidized bed solar heat absorber is shown in FIG. 11 . The solar supercritical carbon dioxide Brayton cycle system in this embodiment is different from the third embodiment in that the addition of The fluidizing gas circulation loop of the solar heat absorber 1 and the fan 18 for loop gas circulation are connected, and the fluidizing gas enters the solar heat absorber 1, so that the solid particles in the solar heat absorber 1 are in a fluidized state, and the fluidized gas is in a fluidized state. The heat is absorbed in the solar heat absorber 1, and the high-temperature fluidized gas after heat absorption is discharged from the solar heat absorber 1 and enters the solar heat storage tank 33 to release heat, and the heat is stored in the solar energy in the form of sensible heat, latent heat or chemical heat. It is stored in the heat storage tank 33, and the low-temperature fluidizing gas after releasing heat enters the solar heat absorber 1 through the fan 18, and circulates.

It should be noted that, in the embodiment of the present invention, the Brayton cycle unit can be selected in various other forms besides the recompression Brayton cycle unit, such as simple Brayton cycle unit, recompression partial cooling Brayton Recycle unit or recompression intercooled Brayton cycle unit. The focusing system of the solar heat absorber can be various focusing systems in the prior art, such as one of a tower concentrating system, a dish concentrating system, a trough concentrating system or a linear Fresnel concentrating system or more. Metal carbonates may also include one or more of lithium, sodium, potassium, rubidium, cesium, francium, beryllium, magnesium, calcium, strontium, barium, or radium carbonates; , rubidium, cesium, francium, beryllium, magnesium, calcium, strontium, barium or radium carbonate modified multi-component mixture. Those skilled in the art can make selections as required, which does not constitute a limitation on the technical solutions of the present invention.

It can be understood by those skilled in the art that, in the above-mentioned embodiments, many technical details are provided for the reader to better understand the present application. However, even without these technical details and various changes and modifications based on the above-mentioned embodiments, the technical solutions claimed in the claims of the present application can basically be realized. Various changes may be made to the above-described embodiments without departing from the spirit and scope of the present invention.

Claims (9)

1. a solar supercritical carbon dioxide Brayton cycle system, in which supercritical carbon dioxide circulates, is characterized in that, comprises: a solar heat absorber, a turbine unit and a Brayton cycle unit, the solar heat absorber and the Brayton cycle unit are respectively connected with the turbine unit through pipelines; also includes a storage tank connected in parallel or in series with the piping between the solar heat absorber and the turbine unit for storing metal carbonates and metal oxides; A gas storage tank is also provided in the Brayton cycle unit for storing supercritical carbon dioxide; When the light conditions are sufficient, the circulating supercritical carbon dioxide absorbs heat in the solar heat absorber; at the same time, the heat transfer medium absorbs heat in the solar heat absorber and transfers it to the metal carbonate in the storage tank, The metal carbonate undergoes a decomposition reaction, stores heat, generates supercritical carbon dioxide, and enters the turbine unit together with the circulating supercritical carbon dioxide to perform external work; the supercritical carbon dioxide after the work passes through the Brayton cycle unit, and a part is stored in the storage tank. In the gas tank, the other part is returned to the solar heat absorber to absorb heat and cycle to do work; When the light conditions are poor or there is no light, the solar heat absorber is isolated, and the supercritical carbon dioxide stored in the gas storage tank and the circulating supercritical carbon dioxide pass through the Brayton cycle unit together and enter the storage tank , undergoes a chemical reaction with metal oxides, releases heat, heats supercritical carbon dioxide, and enters the turbine unit to do external work; The heat absorption medium in the solar heat absorber is supercritical carbon dioxide, and the supercritical carbon dioxide is both a heat transfer medium and a work medium. 2. The solar supercritical carbon dioxide Brayton cycle system according to claim 1, wherein the Brayton cycle unit is a simple Brayton cycle unit, a recompression Brayton cycle unit, and a recompression part cooling Brayton cycle unit Or recompress any of the intercooled Brayton cycle units. 3. The solar supercritical carbon dioxide Brayton cycle system according to claim 1, wherein the Brayton cycle unit comprises: a high temperature regenerator, a low temperature regenerator, a main compressor, a recompressor and a cooler ; The supercritical carbon dioxide after working externally by the turbine unit passes through the high temperature regenerator and the low temperature regenerator, and is divided into two strands, one is cooled by the cooler, the main compressor is pressurized and the After the low-temperature regenerator is heated, it enters the high-temperature regenerator together with another supercritical carbon dioxide pressurized by the recompressor, and then enters the solar heat absorber to absorb heat, and then performs work in a cycle. 4 . The solar supercritical carbon dioxide Brayton cycle system according to claim 3 , wherein the gas storage tank is arranged between the low temperature regenerator and the cooler. 5 . 5. The solar supercritical carbon dioxide Brayton cycle system according to claim 1, wherein the turbine unit comprises a low-pressure turbine, a high-pressure turbine, and a solar thermal storage disposed between the low-pressure turbine and the high-pressure turbine a tank, the solar thermal storage tank is used to store solar heat; The supercritical carbon dioxide entering the turbine unit first enters the high-pressure turbine to do external work, then absorbs heat in the solar heat storage tank, and then enters the low-pressure turbine to do external work. 6. The solar supercritical carbon dioxide Brayton cycle system according to claim 1, characterized in that: the focusing system of the solar heat absorber comprises a tower concentrating system, a dish concentrating system, a trough concentrating system or a One or more of linear Fresnel concentrating systems. 7 . The solar supercritical carbon dioxide Brayton cycle system according to claim 1 , wherein the storage tank is any one of a fixed bed, a bubbling bed, a fluidized bed, a porous medium or a honeycomb ceramic. 8 . 8. The solar supercritical carbon dioxide Brayton cycle system according to claim 7, characterized in that: when the storage tank is a porous medium or a honeycomb ceramic, metal oxide or silicon carbide is used as the matrix, and the metal carbonate is loaded on the the surface of the porous medium or the honeycomb ceramic. 9. The solar supercritical carbon dioxide Brayton cycle system according to claim 1, wherein the metal carbonate comprises lithium, sodium, potassium, rubidium, cesium, francium, beryllium, magnesium, calcium, strontium, barium or one or more of the carbonates of radium; or a multicomponent mixture comprising carbonates of lithium, sodium, potassium, rubidium, cesium, francium, beryllium, magnesium, calcium, strontium, barium or radium modified .

Images