Power Generation System

Abstract

The present invention provides a power generation system, including a heating device, a working device, a cooling device and a pressurizing device connected in sequence through pipelines to form a medium circulation loop, the medium circulation loop is a supercritical carbon dioxide Brayton cycle loop with supercritical carbon dioxide as a circulation medium, and the power generation system also includes a thermochemical heat storage unit, the thermochemical heat storage unit is connected to the heating device, and the thermochemical heat storage unit stores heat energy converted from external energy, or provides a heat source required for the heating device to heat the circulation medium by releasing the stored heat energy. The thermochemical heat storage unit of the present invention can provide a suitable high-temperature heat source for the supercritical carbon dioxide Brayton cycle, and the thermochemical heat storage unit and the supercritical carbon dioxide Brayton cycle are organically combined to realize high-temperature heat storage and heat exchange, effectively improve the overall thermal efficiency of the system, and solve the problems of low thermal efficiency and limited heat storage and heat release temperature range of the existing heat storage system.

Description

Technical Field

[0001] The present invention relates to the technical field of power generation, and in particular to a supercritical carbon dioxide Brayton cycle power generation system based on thermochemical energy storage. Background Art

[0002] The efficient use of renewable energy and advanced energy-saving technologies are important forces to promote the realization of the "dual carbon goals". In recent years, renewable energy such as wind power and photovoltaics have developed rapidly, and the total installed capacity and power generation of renewable energy have soared. However, due to many reasons such as the slowdown in the growth of social electricity demand, the renewable energy absorption capacity is insufficient, and there are still a large number of wind and solar power abandonment; the problem of renewable energy absorption is the result of the long-term unbalanced and uncoordinated development of the energy system. In terms of power peak regulation, thermal power units are still the main peak-shaving power source. In order to reduce carbon emissions, absorb the abandoned power of renewable energy and increase energy utilization, large-scale energy storage technology is urgently needed to effectively absorb valley power and abandoned power in the power system.

[0003] Heat storage is an important component of energy storage. It has diverse temperature grades, flexible scale, safety and low cost. It is widely used in solar thermal power generation and heating, industrial and building energy conservation, equipment thermal management and other fields. It helps to solve the problem of difficult efficient connection between the supply side and the demand side due to time, space or intensity mismatch, effectively improve the comprehensive utilization efficiency of thermal energy, and provide a huge scale of adjustable load for the power grid, improve the peak load regulation capacity of the power grid and the level of renewable energy consumption. The market is huge. Current heat storage technology can be divided into sensible heat storage, latent heat storage and thermochemical heat storage according to the heat storage method. Thermochemical heat storage stores and releases energy through reversible chemical reactions. The energy storage density of thermochemical reaction heat storage is higher than that of sensible heat storage and phase change heat storage, the applicable temperature range is relatively wide, the theoretical energy storage cycle is long, the heat loss is small, and it can be transported over long distances. In theory, it can be applied to the field of medium and high temperature heat storage, and the application prospects are broad.

[0004] At present, the water vapor Rankine cycle is widely used in the fields of fossil energy, nuclear energy and solar thermal power generation. However, water vapor power generation has certain limitations. It is restricted by the temperature resistance limit of metal materials. When the main steam temperature reaches nearly 700°C, the material corrodes seriously. In addition, the inlet pressure of the evaporator and the steam turbine is supercritical pressure, and the end of the steam turbine and the condenser operate under vacuum negative pressure. Due to the low density of the working fluid, the mass flow capacity is weak and the equipment is huge. Supercritical carbon dioxide is non-toxic, harmless, less corrosive and cheap. Due to its low critical parameters (critical pressure 7.38MPa, critical temperature 30.85°C), it is easy to reach the supercritical state for single-phase work, and can couple the hot end above 700°C. The cycle thermal efficiency is significantly higher than the helium and water vapor used commercially on the market.

[0005] At present, there are relatively mature valley power heat storage solutions, but they remain at the research level of the second-generation sensible heat storage technology represented by molten salt. The heat is stored by using valley power and abandoned power to heat the molten salt in the fluidized heat storage tank, and then release heat to do work during the peak period of electricity consumption. Due to the influence of high-temperature corrosion and molten salt decomposition, the average operating temperature of molten salt is 565℃, which greatly limits the overall efficiency of the supercritical carbon dioxide Brayton cycle. Summary of the invention

[0006] In view of the above problems, the present invention provides a power generation system that can achieve high-temperature and high-efficiency energy storage and heat exchange, improve the power generation efficiency of the supercritical carbon dioxide Brayton cycle system, and reduce the operating cost of the system.

[0007] The present invention provides a power generation system, comprising a heating device, a working device, a cooling device and a pressurizing device which are sequentially connected through pipelines to form a medium circulation loop, wherein the medium circulation loop is a supercritical carbon dioxide Brayton cycle loop using supercritical carbon dioxide as a circulation medium, and the power generation system also comprises a thermochemical heat storage unit which is connected to the heating device, and the thermochemical heat storage unit stores heat energy converted from external energy, or provides a heat source required for the heating device to heat the circulation medium by releasing the stored heat energy.

[0008] According to the technical solution, the thermochemical heat storage unit provides a suitable high-temperature (600-850℃) heat source for the supercritical carbon dioxide Brayton cycle, and has the advantages of non-corrosive products, no need for gas storage, low cost, and low technical difficulty. Using supercritical carbon dioxide as the circulation medium has many advantages such as high circulation efficiency, low compression power consumption, compact structure of the working device, small footprint, and low corrosiveness. The organic combination of the thermochemical heat storage unit and the supercritical carbon dioxide Brayton cycle can realize high-temperature heat storage and heat exchange, effectively improve the overall thermal efficiency of the system, and solve the problems of low thermal efficiency and limited temperature range of heat storage and heat release in the existing heat storage system.

[0009] In the optional technical solution of the present invention, the thermochemical heat storage unit includes an external energy supply device, a heat storage tank and a thermochemical heat storage module arranged in the heat storage tank, the external energy supply device is a heat supply device, the heat supply device is connected to the heat storage tank through a first pipeline, and the heat supply device transports hot air into the heat storage tank through the first pipeline to provide the heat energy and gas required for the reaction of the thermochemical heat storage module; the thermochemical heat storage module stores the heat energy converted from the external energy or releases the stored heat energy under the specified temperature conditions;

[0010] The heating device is arranged in the heat storage tank and is in inter-wall heat exchange contact with the thermochemical heat storage module to absorb the heat energy released by the thermochemical heat storage module. The heating device has a working fluid inlet and a working fluid outlet extending to the outside of the heat storage tank. The working fluid inlet is connected to the outlet of the boosting device, and the working fluid outlet is connected to the inlet of the working device. The heat storage tank is provided with a first interface corresponding to the position of the working fluid inlet and a second interface corresponding to the position of the working fluid outlet.

[0011] According to this technical solution, thermal energy can be directly used to generate electricity, which increases the breadth of energy sources for power generation systems and the utilization rate of waste thermal energy; at the same time, it reduces the structural complexity of the system. The thermochemical heat storage module reacts chemically with air under certain temperature conditions to store or release heat. During the heat storage / release process, the entire process only requires reaction with air, and has the advantages of a wide operating temperature range, non-corrosive products, and no need for gas storage. The thermochemical reaction conditions are easy to meet, and the cycle performance of the thermochemical heat storage module is good, which can significantly reduce manufacturing costs.

[0012] In the optional technical solution of the present invention, the thermochemical heat storage unit includes an external energy supply device, a heat storage tank, a thermochemical heat storage module and a reactant supply device, wherein the external energy supply device is a valley power / abandoned power transmission device of the power grid, the valley power / abandoned power transmission device is connected to the thermochemical heat storage module, and provides the electric energy required for the reaction of the thermochemical heat storage module; the thermochemical heat storage module stores the heat energy converted from the electric energy or releases the stored heat energy under the specified temperature conditions;

[0013] The heating device is arranged in the heat storage tank and is in heat exchange contact with the thermochemical heat storage module to absorb the heat released by the thermochemical heat storage module. The heating device has a working fluid inlet and a working fluid outlet. The working fluid inlet is connected to the outlet of the boosting device, and the working fluid outlet is connected to the inlet of the working device. The heat storage tank is provided with a first interface corresponding to the working fluid inlet position and a second interface corresponding to the working fluid outlet position;

[0014] The reactant supply device provides the gas required for the reaction of the thermochemical heat storage module. The heat storage tank is provided with an air inlet and an air outlet. The air inlet is connected to the outlet of the reactant supply device, and the air outlet is connected to the inlet of the reactant supply device. The air outlet is provided with a switch valve.

[0015] According to this technical solution, the external valley electricity / wasted electricity can be converted into thermal energy to provide the thermal energy required for the chemical reaction of the thermochemical heat storage module, thereby improving the utilization rate of valley electricity / wasted electricity and realizing resource recycling. Under certain temperature conditions, the thermochemical heat storage module reacts chemically with the air to store or release heat. During the heat storage / release process, the entire process only requires reaction with the air, and has the advantages of a large operating temperature range, non-corrosive products, and no need for gas storage. The thermochemical reaction conditions are easy to meet, and the cycle performance of the thermochemical heat storage module is good, which can greatly reduce the manufacturing cost.

[0016] In an optional technical solution of the present invention, the reactant supply device is a fan, and the thermochemical heat storage unit also includes an air preheater, the cold end inlet of the air preheater is connected to the outlet of the fan, the cold end outlet of the air preheater is connected to the air inlet, and the hot end inlet of the air preheater is connected to the air outlet.

[0017] According to the technical solution, the fan has a simple structure and can improve the efficiency of air entering the air preheater and the heat storage tank, which is beneficial to improving the efficiency of chemical reactions and thus improving the efficiency of heat storage / release. When releasing heat, the thermochemical heat storage module will discharge air of a certain temperature through the air outlet. The air outlet is connected to the hot end inlet of the air heating device, which can heat the air to be blown into the heat storage tank, reduce heat loss, and improve system efficiency.

[0018] In an optional technical solution of the present invention, the thermochemical heat storage module is a non-conductive metal oxide heat storage material, the power output end of the valley power / abandoned power transmission device is electrically connected to a first electric heating element, and a second electric heating element is provided on the surface of the thermochemical heat storage module, and the first electric heating element and the second electric heating element are electrically connected.

[0019] According to this technical solution, the thermochemical heat storage module is indirectly heated by the electric heating element, which is beneficial to saving the cost of metal oxide heat storage materials; the surface contact between the electric heating element and the thermochemical heat storage module is beneficial to increasing the heating area of ​​the thermochemical heat storage module and improving the thermal conductivity efficiency.

[0020] In an optional technical solution of the present invention, the non-conductive metal oxide includes one or more oxides of lithium, sodium, potassium, lanthanum, cerium, titanium, cobalt, copper, manganese, iron, chromium, aluminum, barium, magnesium, zinc, lead, molybdenum, nickel, zirconium, vanadium, yttrium, neodymium, strontium or calcium, and spinel-based composite metal oxides or perovskite-based composite metal oxides of different crystal forms.

[0021] According to the technical solution, during the heat storage process, the non-conductive metal oxide material in the heat storage material undergoes a reduction reaction under certain temperature conditions and stores heat energy, releasing oxygen to become a low-valent metal oxide; during the heat release process, the low-valent metal oxide undergoes reoxidation, absorbs oxygen to become a high-valent metal oxide, and releases the stored heat energy. The entire process only requires reaction with air, and has the advantages of a wide operating temperature range, non-corrosive products, and no need for gas storage. The thermochemical reaction conditions are easy to meet, and the cycle performance of the thermochemical heat storage module is good, which can greatly reduce the manufacturing cost. After completing the heat release process of the thermochemical energy storage system, the metal oxide material in the heat storage tank will return to the original state of the high-valent metal oxide, waiting for the next round of valley electricity heating.

[0022] In an optional technical solution of the present invention, the thermochemical heat storage module is a metal oxide heat storage material with conductive properties, and the output end of the valley power / abandoned power transmission device is connected to the thermochemical heat storage module through a wire, and an electric energy transmission switch is provided on the wire.

[0023] According to the technical solution, when performing heat storage, the metal oxide heat storage material is directly powered by the valley power / abandoned power transmission device of the power grid, which saves the cost of electric heating elements, simplifies the structural complexity of the supercritical carbon dioxide Brayton cycle system, and realizes the reuse of waste electric energy by converting waste electric energy into thermal energy. Those skilled in the art can flexibly select the heating method of the thermochemical heat storage module according to the different metal oxide heat storage materials to realize the conversion and storage of external electric energy into thermal energy.

[0024] In the optional technical solution of the present invention, the metal oxide heat storage material is a conductive perovskite thermochemical heat storage material, whose general chemical formula is ABO3, and its A-site elements include one or more of lithium, sodium, potassium, lanthanum, strontium, barium, magnesium, neodymium, rubidium, cesium, francium, and beryllium, and the B-site elements include one or more of cerium, titanium, cobalt, copper, manganese, iron, chromium, aluminum, lead, molybdenum, nickel, zirconium, vanadium, and yttrium. The perovskite thermochemical heat storage material can exist in a stable perovskite structure.

[0025] According to this technical solution, suitable metal oxide heat storage materials can be selected as needed, and their heat storage and release temperatures can be adjusted to the appropriate temperature range by means of substitutional element doping. The reference factors for selecting heat storage materials include: heat storage temperature, structural stability, cycle characteristics, heat storage density, electronic conductivity, preparation cost, etc.

[0026] In an optional technical solution of the present invention, the working fluid outlet is connected to a first regulating valve, and the working fluid inlet is connected to a second regulating valve. The first regulating valve controls the flow of the circulating medium entering the working device, and the second regulating valve controls the flow of the circulating medium entering the heating device.

[0027] According to this technical solution, those skilled in the art can choose to start or shut down the supercritical carbon dioxide Brayton cycle as needed. When the supercritical carbon dioxide Brayton cycle is shut down, the system can be used as a thermochemical heat storage device to store heat energy converted from external energy, thereby achieving efficient use of energy.

[0028] In an optional technical solution of the present invention, the supercritical carbon dioxide Brayton cycle loop is a simple Brayton cycle loop, a recompression Brayton cycle loop, a recompression partial cooling Brayton cycle loop or a recompression intermediate cooling Brayton cycle loop.

[0029] According to this technical solution, technicians in this field can select a suitable Brayton cycle loop according to actual conditions. The reference factors for selecting the Brayton cycle loop include: the required scale of distributed energy storage, energy storage temperature, system construction cost, system work efficiency, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic structural diagram of a supercritical carbon dioxide Brayton cycle power generation system based on thermochemical heat storage in the first embodiment of the present invention.

[0031] Figure 2 It is a schematic structural diagram of a heat storage tank in the first embodiment of the present invention.

[0032] Figure 3 It is a schematic structural diagram of a supercritical carbon dioxide Brayton cycle power generation system based on thermochemical heat storage in the second embodiment of the present invention.

[0033] Figure 4 Schematic diagram of the structure of the heat storage tank in the second embodiment of the present invention.

[0034] Figure 5 It is a schematic structural diagram of a supercritical carbon dioxide Brayton cycle power generation system based on thermochemical heat storage in the third embodiment of the present invention.

[0035] Figure 6 It is a schematic structural diagram of a heat storage tank in the third embodiment of the present invention.

[0036] Figure 7 Schematic diagram of the structure of the heat storage tank in the fourth embodiment of the present invention.

[0037] Reference numerals:

[0038] Heating device 1; working fluid inlet 11; working fluid outlet 12; working device 2; cooling device 3; boosting device 4; thermochemical heat storage unit 5; external energy supply device 51; electric energy transmission switch 511; heat storage tank 52; thermochemical heat storage module 521; air inlet 522; air outlet 523; switch valve 524; insulation layer 525; reactant supply device 53; air preheater 54; first electric heating element 551; second electric heating element 552; first regulating valve 61; second regulating valve 62; third regulating valve 63; fourth regulating valve 64; regenerator 7. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] [First embodiment]

[0041] See also Figure 1 As shown, the present invention provides a power generation system, including a heating device 1, a working device 2, a cooling device 3 and a boosting device 4 which are sequentially connected through pipelines to form a medium circulation loop, and the medium circulation loop is a supercritical carbon dioxide Brayton cycle loop with supercritical carbon dioxide as a circulation medium. The power generation system also includes a thermochemical heat storage unit 5, which is connected to the heating device 1, and the thermochemical heat storage unit 5 stores heat energy converted from external energy, or provides the heating device 1 with a heat source required for heating the circulation medium by releasing the stored heat energy.

[0042] Specifically, the thermochemical heat storage unit can convert external energy into thermal energy storage under specified temperature conditions, or react with oxygen to release heat as needed. When releasing heat, the thermochemical heat storage unit exchanges heat with the heating device to provide the heat source required for heating the circulating medium, maintain the operation of the supercritical carbon dioxide Brayton cycle power generation system, and realize the conversion of thermal energy-mechanical energy-electrical energy. Compared with the average operating temperature of molten salt at 565℃, the thermochemical heat storage unit can provide a high-temperature heat source of 600-850℃ for the supercritical carbon dioxide Brayton cycle, and at the same time has the advantages of non-corrosive products, no need for gas storage, low cost, and low technical difficulty. The high-temperature heat source is conducive to improving the overall efficiency of the supercritical carbon dioxide Brayton cycle. Compared with the steam Rankine cycle, the use of carbon dioxide as the circulating medium has the advantages of high cycle efficiency, non-toxicity, low corrosiveness, low compression power consumption, compact structure of the working device, small footprint, and low price. It can reduce corrosion to the equipment under high temperature conditions and increase the service life of the equipment; it is generally believed that when the main steam temperature is higher than 550℃, the cycle efficiency of supercritical carbon dioxide is higher than that of the water vapor Rankine cycle. Carbon dioxide has a low critical parameter and can easily reach a supercritical state to perform single-phase work. The cycle thermal efficiency of the supercritical carbon dioxide Brayton cycle system is significantly higher than that of helium and water vapor. The supercritical carbon dioxide Brayton cycle has the advantages of no restrictions on container materials, simple system design, compact equipment, small scale and high cycle thermal efficiency.

[0043] The present invention couples the thermochemical heat storage unit with the supercritical carbon dioxide Brayton cycle power generation system, which can realize high-temperature heat storage and heat exchange, effectively improve the overall thermal efficiency of the system, realize high-efficiency storage and conversion of surplus energy in external energy, and solve the problems of low thermal efficiency and limited temperature range of heat storage and heat release of existing heat storage systems.

[0044] In a preferred embodiment of the present invention, the thermochemical heat storage unit 5 includes an external energy supply device 51, a heat storage tank 52 and a reactant supply device 53. A thermochemical heat storage module 521 is arranged in the heat storage tank 52. The external energy supply device 51 is a grid valley power / abandoned power transmission device. The external energy supply device 51 is connected to the thermochemical heat storage module 521 and provides the electric energy required for the thermochemical heat storage module 521 to store heat; the thermochemical heat storage module 521 stores the heat energy converted from the electric energy or releases the stored heat energy under the specified temperature conditions; the heating device 1 is arranged in the heat storage tank 52 and is in inter-wall heat exchange contact with the thermochemical heat storage module 521 to absorb the heat released by the thermochemical heat storage module 521, and the heating device 1 It has a working fluid inlet 11 and a working fluid outlet 12, the working fluid inlet 11 is connected to the outlet of the supercharging device 4, and the working fluid outlet 12 is connected to the inlet of the working device 2; the heat storage tank 52 is provided with a first interface corresponding to the position of the working fluid inlet 11 and a second interface corresponding to the position of the working fluid outlet 12; the reactant supply device 53 provides the gas required for the reaction of the thermochemical heat storage module 521, and the heat storage tank 52 is provided with an air inlet 522 and an air outlet 523, the air inlet 522 is connected to the outlet of the reactant supply device 53, the air outlet 523 is connected to the inlet of the reactant supply device 53, and the air outlet 523 is provided with a switch valve 524.

[0045] According to this technical solution, the external valley electricity / wasted electricity can be converted into thermal energy to provide the thermal energy required for the chemical reaction of the thermochemical heat storage module 521, thereby improving the utilization rate of valley electricity / wasted electricity and realizing resource recycling. The thermochemical heat storage module 521 reacts chemically with the air under certain temperature conditions to store or release heat. During the heat storage / release process, the entire process only requires reaction with the air, and has the advantages of a large operating temperature range, non-corrosive products, and no need for gas storage. The thermochemical reaction conditions are easy to meet, and the cycle performance of the thermochemical heat storage module is good, which can greatly reduce the manufacturing cost.

[0046] Specifically, when storing heat, the thermochemical heat storage module 521 undergoes a reduction reaction under certain temperature conditions and releases oxygen, storing part of the heat in the energy provided by the external energy supply device 51 in the form of chemical energy or thermal energy, and ultimately realizing the conversion of external energy into thermal energy and chemical energy storage.

[0047] In the heat release process, by placing the heating device 1 in the heat storage tank 52, driven by the temperature difference, the reverse chemical reaction of the thermochemical heat storage module 52 begins, the thermochemical heat storage module 52 absorbs the oxygen in the heat storage tank 52 to undergo an oxidation reaction, and releases the stored thermal energy and chemical energy in the form of thermal energy. The thermochemical energy storage module 52 and the low-temperature supercritical carbon dioxide perform sufficient heat exchange in the heating device 1, so that the heating device 1 outputs high-temperature supercritical carbon dioxide working fluid, which then enters the working device 2 to generate power, realizing the conversion of thermal energy-mechanical energy-electrical energy, thereby completing the heat release and power supply process of the thermochemical heat storage unit 5. In the heat storage / discharge process, the thermochemical heat storage module 52 only needs to react with the air, and has the advantages of a large operating temperature range, non-corrosive products, no need for gas storage, and the advantages of easy satisfaction of thermochemical reaction conditions. In addition, the thermochemical heat storage module has good cycle performance and can be used multiple times, greatly reducing the manufacturing cost.

[0048] In a specific embodiment of the present invention, the reactant supply device 53 is a fan, and the thermochemical heat storage unit 5 also includes an air preheater 54, the cold end inlet of the air preheater 54 is connected to the outlet of the fan, the cold end outlet of the air preheater 54 is connected to the air inlet 522, and the hot end inlet of the air preheater 54 is connected to the air outlet 523.

[0049] In the above manner, the fan improves the efficiency of air entering the air preheater 54 and the heat storage tank 52, which is beneficial to improving the efficiency of the chemical reaction, and then improving the heat storage / release efficiency. When releasing heat, the thermochemical heat storage module 52 will discharge air of a certain temperature through the air outlet 523. The air outlet 523 is connected to the hot end inlet of the air preheater 54, which can heat the air to be blown into the heat storage tank 52, reduce the heat loss of the Brayton cycle system, and improve the system efficiency.

[0050] In a preferred embodiment of the present invention, the working fluid outlet 12 is connected to the first regulating valve 61, and the working fluid inlet 11 is connected to the second regulating valve 62. The first regulating valve 61 controls the flow of the circulating medium entering the working device 2, and the second regulating valve 62 controls the flow of the circulating medium entering the heating device 1.

[0051] Through the above method, the supercritical carbon dioxide Brayton cycle can be started or shut down as needed. When the supercritical carbon dioxide Brayton cycle is shut down, the system can be used as a thermochemical heat storage device to store heat energy converted from external energy, thereby achieving effective utilization of energy.

[0052] In a preferred embodiment of the present invention, the supercritical carbon dioxide Brayton cycle loop is a simple Brayton cycle loop, a recompression Brayton cycle loop, a recompression partial cooling Brayton cycle loop or a recompression intermediate cooling Brayton cycle loop. Those skilled in the art can select a suitable Brayton cycle loop according to actual conditions. The reference factors for selecting the Brayton cycle unit include: the required scale of distributed energy storage, energy storage temperature, system construction cost, system work efficiency, etc.

[0053] Taking a simple Brayton cycle loop as an example, in a simple Brayton cycle, the heating device 1 is a supercritical carbon dioxide heat exchanger, the working device 2 is a turbine, the cooling device 3 is a condenser, and the boosting device 4 is a compressor. The simple Brayton cycle also includes a regenerator 7, the hot side inlet of the regenerator 7 is connected to the medium outlet of the working device 2, the hot side outlet of the regenerator 7 is connected to the inlet of the cooling device 3, the cold side inlet of the regenerator 7 is connected to the medium outlet of the boosting device 4, and the cold side outlet of the regenerator 7 is connected to the inlet of the heating device 1. The Brayton cycle system has a simple structure and compact equipment, and can effectively absorb the abandoned electricity of distributed renewable energy; the process of the supercritical carbon dioxide Brayton cycle is a common form in this field and will not be repeated here.

[0054] In a preferred embodiment of the present invention, the thermochemical heat storage module 521 is a non-conductive metal oxide heat storage material, the electric energy output end of the valley power / abandoned power transmission device 51 is electrically connected to a first electric heating element 551, and a second electric heating element 552 is provided on the surface of the thermochemical heat storage module 521, and the first electric heating element 551 and the second electric heating element 552 are electrically connected. Indirect heating of the thermochemical heat storage module 521 by the first electric heating element 551 and the second electric heating element 552 is beneficial to saving the cost of metal oxide heat storage materials. The contact between the electric heating element and the surface of the thermochemical heat storage module 521 is beneficial to increase the heating area of ​​the thermochemical heat storage module and improve the thermal conductivity efficiency.

[0055] Preferably, the non-conductive metal oxide includes one or more oxides of lithium, sodium, potassium, lanthanum, cerium, titanium, cobalt, copper, manganese, iron, chromium, aluminum, barium, magnesium, zinc, lead, molybdenum, nickel, zirconium, vanadium, yttrium, neodymium, strontium or calcium, spinel-based composite metal oxides or perovskite-based composite metal oxides of different crystalline forms.

[0056] During the heat storage process of the non-conductive metal oxide materials in the thermochemical heat storage materials, the high-valent metal oxides undergo a reduction reaction under certain temperature conditions and store heat energy, releasing oxygen to become low-valent metal oxides; during the heat release process, the low-valent metal oxides undergo reoxidation, absorb oxygen to become high-valent metal oxides, and release the stored heat energy. The entire process only requires reaction with air, and has the advantages of a wide operating temperature range, non-corrosive products, and no need for gas storage. The thermochemical reaction conditions are easy to meet, and the cycle performance of the thermochemical heat storage module is good, which can greatly reduce the manufacturing cost. After completing the heat release process of the thermochemical energy storage system, the metal oxide material in the heat storage tank will return to the original state of high-valent metal oxides, waiting for the next round of valley power and abandoned power heating.

[0057] In the embodiment of the present invention, suitable metal oxide heat storage materials can be selected as needed, and the heat storage and release temperature can be adjusted to a suitable temperature range by means of substitutional element doping. By controlling and changing the type and proportion of doping elements, the redox reaction temperature range can be adjusted to a suitable heat storage and heat exchange temperature range, which can be better coupled with the supercritical carbon dioxide Brayton cycle system to reduce losses and improve system efficiency.

[0058] Application Scenario

[0059] like Figure 1 , Figure 2 As shown, when the power grid is in the peak and valley of electricity consumption and renewable energy is abandoned, the valley electricity / abandoned electricity can be passed through the valley electricity / abandoned electricity transmission device of the power grid to the first electric heating element 551 and the second electric heating element 552 to heat the thermochemical heat storage module 521 in the heat storage tank 52. The thermochemical heat storage module 521 stores sensible heat and promotes the reduction reaction of the metal oxide heat storage material for thermochemical heat storage, thereby converting the valley electricity / abandoned electricity in the power grid into thermal energy and chemical energy and storing it in the metal oxide heat storage material. At this time, the fan does not operate, the switch valve 524 is opened, and the oxygen generated by the reduction reaction of the metal oxide can be discharged naturally; the first regulating valve 61 and the second regulating valve 62 remain closed, and the supercritical carbon dioxide Brayton cycle system is in a dormant state.

[0060] After the heat storage process is completed, the grid valley power / abandoned power transmission device and the switch valve 524 are closed. The heat storage tank 52 is an insulated storage tank, and the inner wall of the heat storage tank 52 has an insulation layer 525. With the support of the insulation layer 525 of the heat storage tank 52, the stored energy can be maintained for more than 8 hours, and heat can be released to supply power during the peak period of electricity consumption.

[0061] The chemical reactions in the above heat storage process are shown below. In addition to sensible heat storage, thermal energy is stored in the form of chemical energy. (M represents one or more metal elements)

[0062]

[0063] When the power grid is at its peak and the renewable energy power supply is slightly weak, the thermochemical heat storage unit 5 needs to release heat to supply power. At the heat source end, turn on the fan and the switch valve 524, and the air is blown into the cold end of the air preheater 54 by the fan. After preheating, it enters the heat storage tank 53 and undergoes an oxidation reaction with the high-temperature metal oxide heat storage material in the heat storage tank 53, releasing the stored chemical energy to generate heat, and heating the high-pressure supercritical carbon dioxide working fluid in the supercritical carbon dioxide heat exchanger. The high-temperature air discharged from the heat storage tank 52 enters the hot end of the air preheater 54, which is used to heat the air blown in by the fan to reduce the heat loss of the system. At the working end, the first regulating valve 61 and the second regulating valve 62 are opened, and the supercritical carbon dioxide Brayton cycle system is started. The high-temperature and high-pressure supercritical carbon dioxide heat flow (e.g., temperature is 700°C and pressure is 30MPa) generated in the heat storage tank 52 first flows into the working device 2 to do work, and the working device 2 can be connected to a 20MW power generator (not shown in the figure) to generate electricity; after doing work, the supercritical carbon dioxide at 641.11°C and 7.6MPa enters the regenerator 7 as the hot end, and after heat exchange, the supercritical carbon dioxide at 133.04°C and 7.5MPa enters the cooler 3 and is converted into a supercritical carbon dioxide cold flow at 32°C and 7.4MPa, which is compressed by the compressor 4 to produce a high-pressure supercritical carbon dioxide at 128.04°C and 30.2MPa, which enters the cold end of the regenerator 7, and undergoes sufficient heat exchange with the previous high-temperature and medium-pressure supercritical carbon dioxide to produce 557.66°C and 7.6MPa. The 30.1MPa high-pressure supercritical carbon dioxide heat flow returns to the supercritical carbon dioxide heat exchanger in the heat storage tank 52, forming a complete heat release power supply system cycle, realizing the conversion of chemical energy-thermal energy-mechanical energy-electrical energy.

[0064] The chemical reaction in the above exothermic process is shown below, and the stored chemical energy is converted into heat energy for release. (M represents one or more metal elements described in the invention content)

[0065]

[0066] [Second embodiment]

[0067] like Figure 3 , Figure 4 As shown, the third embodiment of the present invention provides a power generation system, and the structure is basically the same as that of the first embodiment and the second embodiment, except that the thermochemical heat storage module 521 is a metal oxide heat storage material with conductive properties, and the output end of the valley power / abandoned power transmission device is connected to the thermochemical heat storage module 521 through a wire, and an electric energy transmission switch 511 is provided on the wire.

[0068] According to the technical solution, when performing heat storage, the metal oxide heat storage material is directly powered by the valley power / abandoned power transmission device of the power grid, which saves the cost of electric heating elements, simplifies the structural complexity of the supercritical carbon dioxide Brayton cycle system, and realizes the reuse of waste electric energy by converting waste electric energy into thermal energy. Those skilled in the art can flexibly select the heating method of the thermochemical heat storage module according to the different metal oxide heat storage materials to realize the conversion and storage of external electric energy into thermal energy.

[0069] The internal structure of the heat storage tank 52 in this embodiment is as follows Figure 4 As shown, the perovskite thermochemical heat storage module in the heat storage tank 52 is honeycomb-shaped, and is made by mixing, pressing and sintering perovskite composite metal oxide powder and a binder. Its resistivity can reach 3Ω·cm at room temperature. As the temperature increases, the resistivity of the heat storage material will continue to decrease, and can reach 0.1Ω·cm or even lower at a temperature of 400-700°C. The specific conductivity depends on the formula of the heat storage material.

[0070] The embodiments of the present invention rely on the electronic conductivity of a specific perovskite metal oxide. During electrical heating, the chemical reactions that occur during the heat storage / release process are shown below. In addition to sensible heat storage, thermal energy is stored in the form of chemical energy. (A and B represent one or more of the metal elements described in the invention)

[0071]

[0072] In a preferred embodiment of the present invention, the metal oxide heat storage material is a conductive perovskite thermochemical heat storage material, whose chemical formula is ABO3, whose A-position elements include one or more of lithium, sodium, potassium, lanthanum, strontium, barium, magnesium, neodymium, rubidium, cesium, francium, and beryllium, and whose B-position elements include one or more of cerium, titanium, cobalt, copper, manganese, iron, chromium, aluminum, lead, molybdenum, nickel, zirconium, vanadium, and yttrium. The perovskite thermochemical heat storage material can exist in a stable perovskite structure. For example, BaCoO3, La x Sr 1-x Co y Fe 1-y O3, Ba x Sr 1-x Co y Fe 1-y O3, La x Ba y Sr 1-x-y Co z Fe 1-z O3, etc.

[0073] In the embodiment of the present invention, suitable metal oxide heat storage materials can be selected as needed, and the heat storage and release temperature can be adjusted to a suitable temperature range by means of substitutional element doping. By controlling and changing the type and proportion of doping elements, the redox reaction temperature range can be adjusted to a suitable heat storage and heat exchange temperature range, which can be better coupled with the supercritical carbon dioxide Brayton cycle system to reduce Loss, improve system efficiency. Furthermore, the reference factors for selecting heat storage materials include: heat storage temperature, structural stability, cycle characteristics, heat storage density, electronic conductivity, preparation cost, etc. A higher heat storage temperature is conducive to ensuring the cycle thermal efficiency of the supercritical carbon dioxide Brayton cycle. Good structural stability and cycle characteristics ensure the durability of the thermochemical heat storage module and save costs. A higher heat storage density ensures the heat storage performance of the thermochemical heat storage module. Excellent electronic conductivity improves the efficiency of converting electrical energy into thermal energy.

[0074] [Third embodiment]

[0075] See also Figure 5 , Figure 6 As shown, in a preferred embodiment of the present invention, the external energy supply device 51 is a heat supply device, and the heat supply device is connected to the air inlet 522 of the heat storage tank 52 through a first pipeline. The heat supply device transports hot air into the heat storage tank 52 through the first pipeline to provide the heat energy and gas required for the reaction of the thermochemical heat storage module 521. Further, the air outlet 523 of the heat storage tank 52 is connected to the inlet of the heat supply device through a second pipeline, and the exhaust gas generated in the heat storage tank 52 enters the heat supply device through the second pipeline, reducing heat loss and realizing the circulation of heat energy, and the exhaust gas generated in the heat storage tank 52 has a high oxygen content. A third regulating valve 63 is provided on the first pipeline, which can conveniently control the gas flow entering the heat storage tank 52, and a fourth regulating valve 64 is provided on the second pipeline, which can conveniently control the gas flow entering the heat supply device.

[0076] In the embodiment of the present invention, by directly utilizing thermal energy to generate electricity, the extensiveness of the energy source of the power generation system and the utilization rate of energy are improved. Specifically, the thermal energy supply device is a solar thermal absorber or other industrial heat source, and the heat collection temperature of the front-end heat absorber of the concentrated solar energy system and the exhaust temperature of some industrial production kilns can reach above 750°C, which can provide sufficient reduction reaction conditions for the metal oxide heat storage material and perform efficient heat storage.

[0077] When heat storage is performed, the third regulating valve 63 and the fourth regulating valve 64 are opened, and the hot air generated by the solar thermal absorber or other industrial heat source enters the heat storage tank 52 through the first pipeline to heat the thermochemical heat storage module 521 therein to realize the heat storage process; the internal structure of the heat storage tank 52 in this embodiment is as follows Figure 6As shown, it is basically the same as the first embodiment and will not be described again.

[0078] [Fourth embodiment]

[0079] The fourth embodiment of the present invention provides a porous silicon carbide loaded metal oxide thermochemical heat storage module, and the internal structure of the corresponding heat storage tank 52 is as follows: Figure 7 The material of the thermochemical heat storage module in the embodiment of the present invention is different from the heat storage materials in the first and second embodiments. The heat storage material is prepared by loading metal oxides on the surface of the porous silicon carbide substrate by an impregnation method using a porous silicon carbide material as a substrate. The thermal conductivity of the thermochemical heat storage module is better than that of a pure metal oxide heat storage module.

[0080] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A power generation system, characterized in that: The invention comprises a heating device, a working device, a cooling device and a pressurizing device which are sequentially connected through pipelines to form a medium circulation loop, wherein the medium circulation loop is a supercritical carbon dioxide Brayton circulation loop with supercritical carbon dioxide as the circulation medium, and the power generation system further comprises a thermochemical heat storage unit, wherein the heating device is arranged in the thermochemical heat storage unit, and the thermochemical heat storage unit stores heat energy converted from external electric energy by a reduction reaction, or releases stored heat energy by an oxidation reaction to provide the heat source required for the heating device to heat the circulation medium; the thermochemical heat storage unit provides a heat source of 600-850°C for the supercritical carbon dioxide Brayton circulation loop, The thermochemical heat storage unit comprises an external energy supply device, a heat storage tank, a thermochemical heat storage module and a reactant supply device, wherein the external energy supply device is a valley power / abandoned power transmission device of the power grid, the valley power / abandoned power transmission device is connected to the thermochemical heat storage module and provides the electric energy required for the reaction of the thermochemical heat storage module; the thermochemical heat storage module stores the heat energy converted from the electric energy or releases the stored heat energy under the specified temperature condition; The heating device is arranged in the heat storage tank and is in heat exchange contact with the thermochemical heat storage module to absorb the heat released by the thermochemical heat storage module. The heating device has a working fluid inlet and a working fluid outlet. The working fluid inlet is connected to the outlet of the boosting device, and the working fluid outlet is connected to the inlet of the working device. The heat storage tank is provided with a first interface corresponding to the working fluid inlet position and a second interface corresponding to the working fluid outlet position. The reactant supply device provides the air required for the reaction of the thermochemical heat storage module, and the heat storage tank is provided with an air inlet and an air outlet, the air inlet is connected to the outlet of the reactant supply device, the air outlet is connected to the inlet of the reactant supply device, and the air outlet is provided with a switch valve; The thermochemical heat storage module is a non-conductive metal oxide heat storage material, the electric energy output end of the valley power / abandoned power transmission device is electrically connected to a first electric heating element, a second electric heating element is provided on the surface of the thermochemical heat storage module, and the first electric heating element is electrically connected to the second electric heating element; or the thermochemical heat storage module is a metal oxide heat storage material with conductive properties, and the output end of the valley power / abandoned power transmission device is connected to the thermochemical heat storage module through a wire.

2. The power generation system according to claim 1, characterized in that: The reactant supply device is a fan, and the thermochemical heat storage unit also includes an air preheater, the cold end inlet of the air preheater is connected to the outlet of the fan, the cold end outlet of the air preheater is connected to the air inlet, and the hot end inlet of the air preheater is connected to the air outlet.

3. The power generation system according to claim 1, characterized in that: The non-conductive metal oxide includes one or more oxides of lithium, sodium, potassium, lanthanum, cerium, titanium, cobalt, copper, manganese, iron, chromium, aluminum, barium, magnesium, zinc, lead, molybdenum, nickel, zirconium, vanadium, yttrium, neodymium, strontium or calcium, and spinel-based composite metal oxides or perovskite-based composite metal oxides of different crystal forms.

4. The power generation system according to claim 1, characterized in that: An electric energy transmission switch is arranged on the conducting wire.

5. The power generation system according to claim 4, characterized in that: The metal oxide heat storage material is a conductive perovskite thermochemical heat storage material, whose general chemical formula is ABO3, whose A-site elements include one or more of lithium, sodium, potassium, lanthanum, strontium, barium, magnesium, neodymium, rubidium, cesium, francium, and beryllium, and whose B-site elements include one or more of cerium, titanium, cobalt, copper, manganese, iron, chromium, aluminum, lead, molybdenum, nickel, zirconium, vanadium, and yttrium. The perovskite thermochemical heat storage material can exist in a stable perovskite structure.

6. The power generation system according to any one of claims 1 to 5, characterized in that: The working medium outlet is connected to a first regulating valve, and the working medium inlet is connected to a second regulating valve. The first regulating valve controls the flow of the circulating medium entering the working device, and the second regulating valve controls the flow of the circulating medium entering the heating device.

7. The power generation system according to any one of claims 1 to 5, characterized in that: The supercritical carbon dioxide Brayton cycle loop is a simple Brayton cycle loop, a recompression Brayton cycle loop, a recompression partial cooling Brayton cycle loop or a recompression intermediate cooling Brayton cycle loop.

Images