Stepped energy storage system

Abstract

The invention provides a stepped energy storage system which comprises a power cycle unit, a high-temperature energy storage unit, a low-temperature energy storage unit, a high-temperature heater, a low-temperature heater and a control unit and is divided into two operation stages including an energy storage mode and an energy release mode. According to the system, the low-temperature energy storage system and the high-temperature energy storage system are combined to achieve stepped energy storage, and through cooperation with the intelligent control unit and the power circulation unit, the system can be flexibly switched between an energy storage mode and an energy release mode, so that the power requirements under different working conditions are accurately responded, and the power supply efficiency is improved. And the # imgabs0 # loss of the high-grade heat energy in the transfer process is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage and power plant peak regulation, and in particular to a stepped energy storage system. Background Art

[0002] The problem of global climate change is becoming increasingly serious, so it is urgent to build a new type of power system. This system needs to ensure the safety of the power grid and the stability of power supply while continuously increasing the supply of green electricity. However, green electricity and new energy generation are intermittent and volatile. With the rapid growth of new energy generation, especially wind and solar energy, the peak-to-valley difference of the power system continues to widen, posing new challenges to the peak-shaving demand of the power system. The current power system regulation capacity is still difficult to fully adapt to the needs of new energy development, resulting in insufficient peak capacity during peak hours of power operation and the coexistence of problems in the valley hours, which has become a prominent problem affecting the balance of power supply and demand and restricting the efficient use of new energy. Therefore, using energy storage systems to balance power supply and demand is a major measure to improve the stability and reliability of the power grid, and is also a key support for promoting the large-scale and high-proportion development of new energy.

[0003] There are two mainstream energy storage systems at present. One is the compressed heat energy storage system, also called the heat pump energy storage system. Its principle is to use the electric energy in the off-peak period to compress the working fluid (such as air, carbon dioxide) to store heat energy, and release the heat energy to generate electricity in the peak period. However, it is limited by the exhaust temperature of the compressor, and its energy storage efficiency is not high. In contrast, the thermochemical energy storage system achieves high heat density and long-term energy storage through reversible chemical reactions. However, in the Rankine cycle of the power plant, a large amount of heat energy is consumed in the low-temperature section of the steam. Thermochemical particles store high-quality heat energy, and using them to heat low-temperature steam will greatly increase the efficiency of the energy storage system. loss, reducing energy storage efficiency. Summary of the invention

[0004] In view of the limitations of the above energy storage system, the present invention proposes a step energy storage system, including a power circulation unit, a high temperature energy storage unit, a low temperature energy storage unit, a high temperature heater, a low temperature heater and a control unit;

[0005] The power circulation unit includes an energy source, a turbine group, a generator and a condenser. The energy source, the turbine group and the condenser are interconnected by pipelines to form a cycle. The turbine group drives the generator to generate electricity.

[0006] The control unit is configured to switch between an energy storage mode and an energy release mode,

[0007] In the energy storage mode, the control unit connects the energy source to the high-temperature energy storage unit and uses the generator to supply energy to the low-temperature energy storage unit;

[0008] In the energy release mode, the control unit connects the high-temperature energy storage unit with the high-temperature heater, and connects the low-temperature energy storage unit with the low-temperature heater. The high-temperature energy storage material of the high-temperature energy storage unit flows into the hot side of the high-temperature heater, and the circulating working fluid of the power circulation unit flows into the cold side of the high-temperature heater. The low-temperature energy storage material of the low-temperature energy storage unit flows into the hot side of the low-temperature heater, and the circulating working fluid of the power circulation unit flows into the cold side of the low-temperature heater.

[0009] According to the technical solution, in the energy storage mode, the power circulation unit directly absorbs the heat energy of the energy source and converts it into electrical energy through the turbine and the generator; the control unit connects the energy source with the high-temperature energy storage unit, and the high-temperature energy storage material absorbs the heat energy of the energy source and converts it into other forms of energy for storage. This energy storage method has the advantages of high energy density and long-term storage stability; at the same time, the generator supplies energy to the low-temperature energy storage unit, and the low-temperature energy storage unit converts the electrical energy into other forms of energy and stores it. In the energy release mode, the control unit connects the high-temperature energy storage unit with the high-temperature heater, and connects the low-temperature energy storage unit with the low-temperature heater. The high-temperature energy storage unit and the low-temperature energy storage unit release the stored energy in the form of heat energy through the high-temperature and low-temperature heaters respectively, and the power circulation unit absorbs the heat energy of the above low-temperature heater and the high-temperature heater in turn and converts it into electrical energy through the turbine and the generator.

[0010] Through the organic combination of four units and two heaters, the step-by-step utilization of different grades of energy is achieved, effectively reducing the high-grade heat energy in the transmission process. It reduces power losses, improves the energy efficiency of the overall system, and enables flexible regulation of power while ensuring efficient power generation.

[0011] Optionally, the high-temperature energy storage unit of the stepped energy storage system provided by the present invention stores energy through thermochemical materials, sensible heat materials and / or phase change materials.

[0012] According to the technical solution, thermochemical material energy storage refers to the process of realizing energy storage and heat release by using the reversible thermochemical reaction of thermochemical materials. In the endothermic reaction stage, energy is stored by breaking chemical bonds; in the exothermic reaction stage, energy is released by generating chemical bonds. Its main advantage is that thermochemical materials have a large energy storage density and a high heat storage temperature range. At the same time, thermochemical materials are stored in the form of chemical energy at ambient temperature, and can store energy losslessly for a long time at a temperature close to ambient temperature. The forward-reverse reaction of thermochemical materials can be carried out at high temperature and obtain high-grade thermal energy. There are no problems such as supercooling and phase separation, and the instantaneous release power of thermal energy is very large. It is safe and non-toxic, low-priced, and its use is not restricted by time and space.

[0013] Sensible heat material energy storage refers to an energy storage technology developed by utilizing the characteristics that each substance has a certain heat capacity and absorbs or releases heat as the temperature changes while the material form remains unchanged. Sensible heat energy storage technology realizes the energy storage process through the change of the temperature of the energy storage medium. Since direct contact heat exchange can be used, or the fluid itself is the heat storage medium, the heat storage and release process is relatively simple. Sensible heat material energy storage can be specifically divided into solid sensible heat storage, liquid sensible heat storage and liquid-solid combined sensible heat storage. Among them, solid energy storage can be divided into bedrock energy storage, silicon energy storage, steel energy storage, concrete energy storage, aluminum alloy energy storage, solid crushed stone energy storage, volcanic rock energy storage, etc. according to different energy storage materials. The biggest advantage of sensible heat material energy storage is simple operation, low cost, long service life and high thermal conductivity.

[0014] Phase change energy storage is a method of storing and releasing thermal energy by utilizing the characteristics of energy storage materials absorbing and releasing latent heat of phase change during phase change, so it is also called latent heat energy storage. Energy storage media that utilize latent heat of phase change to store energy are often called phase change materials. Phase change materials absorb or release a large amount of heat during phase change, and this characteristic makes phase change materials an excellent energy storage medium. Phase change energy storage is characterized by medium energy storage density and small system volume. At the same time, the phase change process is stable, and the energy storage and heat release processes are well controllable.

[0015] Optionally, the low-temperature energy storage unit of the stepped energy storage system provided by the present invention stores energy through heat pumps and / or thermochemical materials.

[0016] Heat pump energy storage is a large-scale long-term energy storage technology that establishes a high and low temperature difference through a heat pump cycle, and then drives a heat engine cycle to generate electricity through the temperature difference. Its main advantage is that it is not restricted by geographical conditions and can be deployed and applied in a variety of environments, which provides greater flexibility and convenience for the construction and operation of energy storage systems. At the same time, the heat pump energy storage system can store energy for a long time, and the energy storage time range is usually between 4 and 24 hours, which enables it to meet energy needs on different time scales. The efficiency of the heat pump energy storage system is relatively high. The electrical efficiency of a high-power level system can reach more than 65%, and the overall system efficiency can even exceed 95%.

[0017] When the low-temperature energy storage unit stores energy through a heat pump, the heat pump energy storage circuit includes a compressor, a cooler, a turbine and an energy storage medium tank. The cold side flow paths of the compressor, the cooler, the turbine and the condenser are connected in sequence.

[0018] In the energy storage mode, the compressor is powered by the generator, and the energy storage working fluid in the energy storage working fluid tank exchanges heat with the working fluid flowing out of the compressor using a cooler;

[0019] In the energy release mode, the energy storage working fluid in the energy storage working fluid tank exchanges heat with the circulating working fluid in the power circulation unit using a low-temperature heater.

[0020] According to this technical solution, the traditional low-temperature energy storage unit only relies on compressed working fluid (such as refrigerant) for energy storage, but the energy storage efficiency of compressed working fluid is limited. The introduction of energy storage working fluid with higher energy storage efficiency can store more energy in the low-temperature energy storage unit. This energy storage working fluid exchanges heat with the compressed working fluid in the energy storage mode, transfers heat energy to the energy storage working fluid, and realizes efficient energy storage.

[0021] Compared with the compressed energy storage of working fluids, the thermal energy stored by thermochemical materials is of higher quality. According to the reaction characteristics, the thermochemical material energy storage system can be divided into chemical reaction heat storage (based on the reversible reaction of different chemical substances), adsorption heat storage (based on the accumulation or aggregation of adsorbates on the surface of adsorbents) and absorption heat storage (based on the dissolution or penetration of absorbates in absorbents). According to the working temperature, it can be divided into medium and low temperature thermochemical energy storage materials and high temperature thermochemical energy storage materials. High temperature thermochemical energy storage materials can be further divided into metal hydride systems, organic systems, redox systems, inorganic hydroxide systems, ammonia synthesis and decomposition systems, carbonate thermal decomposition systems, etc.

[0022] It can be selectively applied in the heat pump energy storage system and the thermochemical energy storage system according to the specific situation of the low-temperature energy storage unit, or the two systems can be used at the same time.

[0023] Optionally, the control unit of the step energy storage system provided by the present invention is configured as follows:

[0024] In response to the external power grid to which the generator is connected being in a load valley interval, configuring the step energy storage system to an energy storage mode;

[0025] In response to the external power grid connected to the generator being in a load peak interval, the stepped energy storage system is configured to be in an energy release mode.

[0026] According to the technical solution, the control unit intelligently determines the load status of the power grid based on preset programs and algorithms, and automatically switches the energy storage and release modes to adapt to power grid fluctuations, thereby reducing manual operations and improving system efficiency and reliability. The system switches the energy storage and release modes during power operation peaks and valleys, allowing the energy storage system to operate efficiently under different operating conditions and optimize energy distribution and utilization. The intervention of the control unit enables the energy storage system to provide stable power support when the power grid fluctuates.

[0027] Optionally, the power circulation unit also includes a circulation pump and a regenerator. The energy source, turbine group, condenser, circulation pump and regenerator are connected in sequence to form a circulation. The cold side flow path of the regenerator is connected to the circulation, and the medium-pressure working fluid from the turbine group flows into the hot side of the regenerator. The hot side flow outlet of the regenerator is connected to the condenser.

[0028] According to the technical solution, the regenerator plays the role of preheating the working fluid in the power circulation unit. Part of the medium-pressure working fluid extracted from the turbine group passes through the hot side flow path of the regenerator to exchange heat with the working fluid that is about to enter the energy source for heat absorption. In this process, the heat released by the medium-pressure working fluid is absorbed by the working fluid that is about to enter the energy source, thereby realizing the preheating of the working fluid. Through the preheating effect of the regenerator, the temperature of the working fluid entering the energy source is increased, thereby reducing the temperature fluctuation in the energy source. This reduction in temperature fluctuation helps to distribute heat more evenly in the energy source and avoids the decrease in thermal efficiency caused by excessive temperature gradient. The main role of the circulating pump in the power circulation unit is to pressurize the working fluid. By increasing the pressure of the working fluid, the circulating pump can increase the flow rate and flow of the working fluid, thereby ensuring the smooth circulation of the working fluid in the system. The increase in the flow rate of the working fluid helps to improve the circulation efficiency of the system. In the same time, more working fluid can flow through components such as the energy source, turbine group and condenser, thereby improving the overall output power and energy conversion efficiency of the system. The stable operation of the circulating pump helps to maintain the pressure and flow rate of the working fluid in the system stable, thereby enhancing the stability of the system.

[0029] Furthermore, in the energy release mode, the turbine group, the condenser, the circulation pump, the regenerator, the low-temperature heater and the high-temperature heater are sequentially connected to form a cycle.

[0030] During the period of low power operation, the power generation of the power circulation unit is higher than the power demand, so the excess energy needs to be stored. The control unit controls the system to operate in energy storage mode.

[0031] During peak hours of power operation, the amount of thermal energy generated in the power cycle cannot meet the power demand, so it is necessary to add a new energy source to the power cycle. The control unit controls the system to operate in energy release mode.

[0032] According to the technical solution, the energy storage mode can make full use of the electricity during the off-peak period and avoid the waste of electricity. Through thermal energy storage, thermal energy can be released during peak hours, reducing dependence on the power grid, realizing the staggered use of electricity, and helping to maintain the stable operation of the power grid. During the peak period of power operation, the power generation of thermal energy in the power cycle cannot meet the power demand. At this time, the control unit switches the system to the energy release mode, using the high-temperature heater to release the thermal energy in the high-temperature energy storage unit and convert it into electrical energy. At the same time, the low-temperature heater uses the energy storage fluid of the low-temperature energy storage unit to release thermal energy, providing an additional energy source for the power cycle. The energy release mode can provide additional power support during peak hours to meet the power demand of the power grid. This helps to avoid power outages or power restrictions due to insufficient power in the power grid and ensure the stability of power supply.

[0033] Furthermore, the high temperature heater includes a first high temperature heater. In the energy release mode, the high temperature energy storage unit utilizes the first high temperature heater to heat the circulating working fluid flowing out of the low temperature heater.

[0034] According to the technical solution, when the thermal energy generation in the power circulation unit cannot meet the power demand, the control unit will start the energy release mode. The low-temperature heater is responsible for transferring the thermal energy of the energy storage working fluid to the circulating working fluid. The first high-temperature heater further heats the circulating working fluids that have been heated by the low-temperature heater, realizing the cascade utilization of thermal energy. This synergistic effect helps to improve the thermal energy conversion efficiency and energy utilization of the entire system. The introduction of the first high-temperature heater enables the system to more efficiently utilize the thermal energy in the high-temperature energy storage unit in the energy release mode. This not only increases the output power of the system, but also reduces the energy consumption and operating costs of the system. At the same time, since the first high-temperature heater can heat the circulating working fluid to a higher temperature, it also helps to improve the power generation efficiency of the turbine group.

[0035] Furthermore, the turbine group includes a high-pressure turbine, a medium-pressure turbine and a low-pressure turbine which are connected in sequence and connected to the generator. The high-temperature heater also includes a second high-temperature heater. In the energy release mode, the hot side flow path of the second high-temperature heater is connected to the high-temperature energy storage unit, the cold side inlet of the second high-temperature heater is connected to the high-pressure turbine, and the cold side outlet of the second high-temperature heater is connected to the medium-pressure turbine.

[0036] According to this technical solution, the design of the power cycle unit of a single turbine is relatively simple, and the manufacturing, installation and maintenance costs are relatively low. However, it also has the disadvantage of low work efficiency and cannot fully utilize the thermal energy under different pressures; the adaptability of the single turbine unit to different energy sources and pressure conditions is also poor.

[0037] The multi-turbine unit composed of a high-pressure turbine, a medium-pressure turbine and a low-pressure turbine can make fuller use of heat energy at different pressures by expanding and working step by step, thereby improving the efficiency of the entire cycle. At the same time, the multi-turbine unit can also be adjusted according to different energy sources and pressure conditions to adapt to different application scenarios. For example, under a high-pressure energy source, the high-pressure turbine can first expand and work; under medium and low-pressure energy sources, the medium-pressure and low-pressure turbines can expand and work in turn. However, due to its complex structure, in actual applications, it is necessary to accurately control the speed, flow rate and other parameters of each turbine to ensure the stable operation of the entire system. At the same time, each turbine also needs to be regularly maintained and overhauled to ensure its long-term stable operation.

[0038] In summary, single turbine units and multi-turbine units each have their own advantages and disadvantages. In practical applications, it is necessary to choose according to the specific application scenario and needs. If you pursue simple structure, convenient operation and low cost, you can choose a single turbine unit; if you pursue high efficiency, strong adaptability and good flexibility, you can choose a multi-turbine unit.

[0039] Optionally, the energy source is a boiler, a solar heat source, a wind heat source and / or a nuclear heat source.

[0040] Optionally, the power cycle unit is a steam Rankine cycle, a supercritical thermal power unit, an ultra-supercritical thermal power unit, a CO 2 Brayton cycle or CO 2 Rankine cycle.

[0041] Optionally, the working fluid of the cryogenic energy storage unit may be air, CO2 or argon.

[0042] Optionally, the low-temperature energy storage unit stores energy through a heat pump, and the working fluid of the heat pump absorbs waste heat of the circulating working fluid through a condenser of the power circulation unit or directly takes heat from the air before being compressed.

[0043] The low-temperature energy storage unit itself has a certain degree of flexibility and adaptability, and can use a variety of energy sources for energy storage. Using the waste heat of circulating working fluids for energy storage can not only reduce energy consumption in industrial production, but also reduce environmental pollution and realize the recycling of resources. Air as an energy source has the characteristics of universality and easy access. The air is compressed and stored in the air compressor, and the heat energy can be released when needed to generate electricity or heat. This energy source does not require additional fuel consumption and has little impact on the environment.

[0044] Optionally, the energy storage path of the low-temperature energy storage unit through the heat pump energy storage can be an open circuit, that is, the working fluid is finally discharged to the outside; the energy storage path can also be a closed cycle, that is, the working fluid again absorbs the waste heat after the circulating working fluid does work and heats up to perform a heat pump cycle.

[0045] The open circuit system is relatively simple, because the working fluid is directly discharged to the outside after completing the work, and no additional circulation equipment and pipelines are required. At the same time, direct discharge also avoids the problem of system efficiency reduction caused by the waste heat of the working fluid. But on the other hand, the waste heat after the working fluid does work is directly discharged to the outside, and this part of the energy is not fully utilized, resulting in low overall energy utilization efficiency.

[0046] In a closed cycle, the waste heat after the working fluid does work is absorbed again for heating, thus realizing the heat pump cycle and improving energy utilization efficiency.

[0047] In summary, the system combines low-temperature energy storage system and high-temperature energy storage system and applies them together to power cycle power generation. The operation efficiency of the energy storage system is ensured by using different grades of thermal energy in a step-by-step manner. Such step-by-step utilization of thermal energy is not only conducive to reducing the high-grade thermal energy in the transmission process, but also to reducing the high-grade thermal energy in the transmission process. damage. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a structural schematic diagram of a stepped energy storage system in energy storage mode according to an embodiment of the present invention.

[0049] Figure 2 It is a structural schematic diagram of a step energy storage system in an energy release mode according to an embodiment of the present invention.

[0050] Description of reference numerals:

[0051] 1-high-pressure turbine; 2-medium-pressure turbine; 3-low-pressure turbine; 4-condenser; 5-circulation pump; 6-regenerator; 7-generator; 8-first thermochemical storage tank; 9-second thermochemical storage tank; 10-energy storage medium low-temperature tank; 11-energy storage medium high-temperature tank; 12-boiler; 13-compressor; 14-cooler; 15-turbine; 16-low-temperature heater; 17-first high-temperature heater; 18-second high-temperature heater; 100-thermochemical energy storage unit; 200-heat pump energy storage unit; 300-power circulation unit; 400-control unit. DETAILED DESCRIPTION

[0052] 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 system personnel in this field without creative work are within the scope of protection of the present invention.

[0053] This embodiment is a step energy storage system based on a heat pump and a thermochemical energy storage system, wherein the high temperature energy storage unit is a thermochemical energy storage unit 100, and the low temperature energy storage unit is a heat pump energy storage unit 200. The step energy storage system in this embodiment also includes a power circulation unit 300 and a control unit 400, and is divided into two operating stages: an energy storage mode and an energy release mode.

[0054] During the low-power period, the power generation of the power circulation unit 300 is higher than the power demand, and the excess energy needs to be stored. The control unit 400 controls the thermochemical energy storage unit 100 to connect with the boiler 12, and controls the generator 7 to supply energy to the compressor 13 of the heat pump energy storage unit 200. Part of the excess energy of the boiler 12 in the power circulation unit 300 is stored in the form of high-grade thermal energy through the thermochemical energy storage unit; the other part is input into the heat pump energy storage unit in the form of electrical energy and stored together with low-grade waste heat, where the electrical energy is used to drive the compressor 13 of the heat pump energy storage unit 200.

[0055] The power circulation unit 300 in the energy storage mode is connected in sequence by a circulation pump 5, a regenerator 6, a boiler 12, a high-pressure turbine 1, a medium-pressure turbine 2, a low-pressure turbine 3 and a condenser 4 to form a steam Rankine cycle loop. There is also a secondary heat absorption path between the high-pressure turbine 1, the boiler 12 and the medium-pressure turbine 2.

[0056] Specifically, the liquid power circulating medium is first pressurized by the circulating pump 5, and then enters the regenerator 6 and the boiler 12 in turn to absorb heat and vaporize, and then enters the high-pressure turbine 1 to expand and do work; the circulating medium after doing work returns to the boiler 12 through the secondary heat absorption path for secondary heat absorption, and then enters the medium-pressure turbine 2 and the low-pressure turbine 3 in turn to expand and do work respectively; the work done by the high-pressure turbine 1, the medium-pressure turbine 2, and the low-pressure turbine 3 is converted into electrical energy by the generator 7; finally, the circulating medium after doing work enters the condenser 4 from the outlet of the low-pressure turbine 3 to release waste heat and is condensed back to liquid; the liquid power circulating medium returns to the circulating pump 5 to start the next cycle.

[0057] The power circulation unit 300 in the energy storage mode also has a heat recovery path, that is, a small amount of gaseous circulating working fluid is respectively extracted from the high-pressure turbine 1, the medium-pressure turbine 2, and the low-pressure turbine 3 to the regenerator 6, and heat is exchanged with the liquid circulating working fluid before entering the boiler 12, so that the liquid circulating working fluid is preheated before entering the boiler 12. The gaseous circulating working fluid in the regenerator 6 condenses into liquid in the process of releasing heat, and these liquid circulating working fluids enter the condenser 4 for further cooling, and then are sent to the circulation pump 5 to start the next cycle.

[0058] Through the preheating operation of the regenerator 6, the temperature of the circulating working fluid entering the boiler 12 is increased, thereby increasing the average temperature of the circulating heat absorption process. This helps to reduce the loss of cold sources and improve the thermal efficiency of the cycle. It should be noted that although the liquid circulating working fluid is heated during the heat recovery process, its temperature can usually only reach the saturation temperature under the extraction pressure. In addition, in order to maintain the stability and efficiency of the stepped energy storage system, the share and parameters of the heat recovery extraction need to be specifically designed and controlled according to the actual scale and efficiency of the power circulation unit 300, and there is no restriction on it here.

[0059] In the steam Rankine cycle used in this embodiment, water vapor is the core circulating medium, which undergoes a transformation process from liquid to gas and then from gas back to liquid, thereby realizing the conversion of thermal energy into mechanical energy.

[0060] The thermochemical energy storage unit 100 in the energy storage mode is composed of a first thermochemical particle storage tank 8, a boiler 12 and a second thermochemical particle storage tank 9 connected in sequence to form a first energy storage path.

[0061] Specifically, the thermochemical particles first enter the boiler 12 from the first thermochemical particle storage tank 8 to absorb heat and decompose, and the high-grade thermal energy in the boiler 12 is stored in the thermochemical particles in the form of chemical energy. The stored thermochemical particles enter the second thermochemical particle storage tank 9 for storage.

[0062] The heat pump energy storage unit 200 in energy storage mode includes a working path composed of a condenser 4, a compressor 13, a cooler 14, and a turbine 15 connected in sequence, and a second energy storage path composed of a low-temperature energy storage tank 10, a cooler 14, and a high-temperature energy storage tank 11 connected in sequence.

[0063] In the heat pump energy storage unit 200, the working fluid first enters the condenser 4 to absorb the waste heat of the power cycle working fluid, and then enters the compressor 13 to be compressed to a high-pressure and high-temperature state. The high-pressure and high-temperature working fluid first releases heat energy through the cooler 14, then enters the turbine 15 to recover part of the expansion work, and finally is discharged into the atmosphere. Among them, the heat energy released by the high-pressure and high-temperature working fluid in the cooler 14 is absorbed by the energy storage working fluid in the energy storage working fluid low-temperature tank 10, and the energy storage working fluid after absorbing heat and heating is input into the energy storage working fluid high-temperature tank 11 for storage.

[0064] The compressor 13 is directly connected to the generator 7 of the power circulation unit 300 , and the generator 7 provides electric energy to drive the compressor 13 to pressurize the working fluid of the heat pump energy storage unit 200 .

[0065] In other embodiments, after the turbine 15 expands and does work, the working fluid can also return to the condenser 4 again to absorb the waste heat after the circulating working fluid has done work and heat it up to perform a heat pump cycle. The open-loop system in which the working fluid is discharged into the atmosphere is simple and does not require additional equipment, which avoids the decrease in efficiency caused by the waste heat of the working fluid, but the direct discharge of waste heat will also lead to low energy utilization efficiency. The closed-loop cycle recycles the waste heat of the working fluid for the next round of heating, which improves energy efficiency, but the waste heat needs to be reasonably managed to prevent system problems and avoid system efficiency reduction or failure caused by waste heat accumulation. In practical applications, it is necessary to selectively apply the open path and the closed-loop cycle according to specific requirements, or it can be designed as a dual-use system that can be switched between the open path and the closed-loop cycle. The dual-use system combines the advantages of the open-loop system and the closed-loop cycle to achieve a balance between energy utilization efficiency and system complexity. In practical applications, it is necessary to switch according to specific requirements and conditions to give full play to the comprehensive advantages of the two systems.

[0066] During the peak period of power operation, that is, when the external power grid is in the peak load range, the heat load of the boiler 12 cannot meet the required power, and a new energy source needs to be added to the power circulation unit 300. Therefore, the thermal energy stored in the thermochemical energy storage unit and the heat pump energy storage unit in the energy storage mode is used as an additional energy source for power generation of the power circulation unit 300. The control unit 400 connects the thermochemical energy storage unit 100 with the first high temperature heater 17 and the second high temperature heater 18, and connects the heat pump energy storage unit 200 with the low temperature heater 16.

[0067] Specifically, the thermochemical energy storage unit 100 in the energy release mode is connected in series with the second thermochemical particle storage tank 9, the first high temperature heater 17, and the first thermochemical particle storage tank 8, and the second high temperature heater 18 is connected in parallel with the first high temperature heater 17, forming a first heating path. After the thermochemical particles flow out of the second thermochemical particle storage tank 9, they are divided into two streams and enter the first high temperature heater 17 and the second high temperature heater 18 respectively. In this process, the thermochemical particles react with oxygen to release heat.

[0068] The heat pump energy storage unit 200 in the energy release mode is composed of a high-temperature energy storage medium tank 11, a low-temperature heater 16, and a low-temperature energy storage medium tank 10 connected in sequence to form a second heating path.

[0069] The energy storage medium enters the low temperature heater 16 from the energy storage medium high temperature tank 11 to release heat energy, and the energy storage medium after heat release enters the energy storage medium low temperature tank 10 for storage.

[0070] The energy release mode power circulation unit 300 is composed of a circulation pump 5, a regenerator 6, a low-temperature heater 16, a first high-temperature heater 17, a high-pressure turbine 1, a second high-temperature heater 18, a medium-pressure turbine 2, a low-pressure turbine 3 and a condenser 4 connected in sequence to form a steam Rankine cycle loop.

[0071] The liquid power circulating medium is first pressurized by the circulating pump 5, then enters the regenerator 6 to absorb heat, and then enters the low-temperature heater 16 from the outlet of the regenerator 6 to absorb the low-grade thermal energy stored in the heat pump energy storage unit 200, and then enters the first high-temperature heater 17 to absorb the high-grade thermal energy stored in the thermochemical particles, and then enters the high-pressure turbine 1 to expand and do work. After doing work, the circulating medium enters the second high-temperature heater 18 to continue to absorb thermal energy from the thermochemical energy storage unit 100, and then enters the medium-pressure turbine 2 and the low-pressure turbine 3 in turn to expand and do work; the work done by the high-pressure turbine 1, the medium-pressure turbine 2, and the low-pressure turbine 3 is converted into electrical energy through the generator 7; finally, the circulating medium after doing work enters the condenser 4 from the outlet of the low-pressure turbine 3 to release the residual heat and condense back into liquid, and the liquid power circulating medium returns to the circulating pump 5 to start the next cycle.

[0072] The power circulation unit 300 in the energy release mode also has a heat recovery path, that is, a small amount of gaseous circulating working fluid is respectively extracted from the high-pressure turbine 1, the medium-pressure turbine 2, and the low-pressure turbine 3 to the regenerator 6, and heat is exchanged with the liquid circulating working fluid before entering the low-temperature heater 16, so that the liquid circulating working fluid is preheated before entering the low-temperature heater 16. The gaseous circulating working fluid in the regenerator 6 condenses into liquid in the process of releasing heat, and these liquid circulating working fluids enter the condenser 4 for further cooling, and then are sent to the circulation pump 5 to start the next cycle.

[0073] 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 stepped energy storage system, characterized in that: It includes a power circulation unit, a high temperature energy storage unit, a low temperature energy storage unit, a high temperature heater, a low temperature heater and a control unit; The power circulation unit includes an energy source, a turbine group, a generator and a condenser. The energy source, the turbine group and the condenser are interconnected by pipelines to form a cycle. The turbine group drives the generator to generate electricity. The control unit is configured to switch between an energy storage mode and an energy release mode, In the energy storage mode, the control unit connects the energy source to the high-temperature energy storage unit and uses the generator to supply energy to the low-temperature energy storage unit; In the energy release mode, the control unit connects the high-temperature energy storage unit with the high-temperature heater, and connects the low-temperature energy storage unit with the low-temperature heater, the high-temperature energy storage material of the high-temperature energy storage unit flows into the hot side of the high-temperature heater, the circulating working fluid of the power circulation unit flows into the cold side of the high-temperature heater, the low-temperature energy storage material of the low-temperature energy storage unit flows into the hot side of the low-temperature heater, and the circulating working fluid of the power circulation unit flows into the cold side of the low-temperature heater.

2. The step energy storage system according to claim 1, characterized in that: The high temperature energy storage unit stores energy via thermochemical materials, sensible heat materials and / or phase change materials.

3. The step energy storage system according to claim 1, characterized in that: The low temperature energy storage unit stores energy via a heat pump and / or thermochemical materials.

4. The step energy storage system according to claim 1, characterized in that: The control unit is configured as follows: In response to the external power grid connected to the generator being in a load valley interval, configuring the stepped energy storage system to an energy storage mode; In response to the external power grid to which the generator is connected being in a load peak interval, the stepped energy storage system is configured to be in an energy release mode.

5. The step energy storage system according to claim 1, characterized in that: The power circulation unit also includes a circulation pump and a regenerator. The energy source, the turbine group, the condenser, the circulation pump and the regenerator are connected in sequence to form a circulation. The cold side flow path of the regenerator is connected to the circulation, and the hot side of the regenerator flows into the medium-pressure working fluid from the turbine group. The hot side flow outlet of the regenerator is connected to the condenser.

6. The step energy storage system according to claim 5, characterized in that: In the energy release mode, the turbine group, the condenser, the circulation pump, the regenerator, the low-temperature heater and the high-temperature heater are sequentially connected to form a cycle.

7. The step energy storage system according to claim 6, characterized in that: The high temperature heater includes a first high temperature heater. In the energy release mode, the high temperature energy storage unit uses the first high temperature heater to heat the circulating working fluid flowing out of the low temperature heater.

8. The step energy storage system according to claim 7, characterized in that: The turbine group includes a high-pressure turbine, a medium-pressure turbine and a low-pressure turbine which are connected in sequence and connected to the generator. The high-temperature heater also includes a second high-temperature heater. In the energy release mode, the hot side flow path of the second high-temperature heater is connected to the high-temperature energy storage unit, the cold side inlet of the second high-temperature heater is connected to the high-pressure turbine, and the cold side outlet of the second high-temperature heater is connected to the medium-pressure turbine.

9. The step energy storage system according to claim 1, characterized in that: The energy source is a boiler, a solar heat source, a wind heat source and / or a nuclear heat source.

10. The step energy storage system according to claim 1, characterized in that: The power cycle unit is a steam Rankine cycle, a supercritical thermal power unit, an ultra-supercritical thermal power unit, a CO2 Brayton cycle or a CO2 Rankine cycle.

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