Heat storage coal-fired thermodynamic system based on steam cascade power generation

Abstract

The invention relates to the technical field of steam engine devices, and discloses a heat storage coal-fired thermodynamic system based on steam cascade power generation, which comprises a coal-fired unit comprising a boiler, a turbine module and a power generator which are connected with each other, and the turbine module comprises a high-pressure turbine, a medium-pressure turbine and a low-pressure turbine which are connected in series; a heat exchanger assembly is further connected between the boiler and the turbine module; the heat storage power generation device is composed of a silicon-based heat storage layer, a thermal electron device and an electric heater which are coaxially arranged, the silicon-based heat storage layer covers the outer side of the thermal electron device, and the electric heater is located on the outer side of the silicon-based heat storage layer; the electric heater is connected with the silicon-based heat storage layer through a high-temperature-resistant pipeline, a thermoelectric conversion channel is formed between a cathode and an anode of the hot electron device, and the anode hot end is connected with an inlet of a steam pipeline. The problems of limited heat storage temperature, insufficient utilization of latent heat of steam, high minimum power load and slow dynamic response in the prior art are solved, and the purposes of increasing the heat storage temperature, flexible peak regulation and improving the response speed and efficiency are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of mechanical engineering, and in particular to a steam engine device. Background Art

[0002] Amidst the global energy transition, renewable energy is rapidly developing but unstable. Coordinated peak-shaving in coal-fired power plants (CFPPs) is limited by the boiler's minimum stable combustion load when used in conjunction with renewable energy. This paper proposes a thermal storage-coal-fired thermal system based on a thermionic-steam cascade power generation system. This system utilizes a unique cylindrical thermal storage device with a silicon-based thermal storage medium on the outside, a thermionic cathode and cathode in the middle layer, and water vapor flowing through the tubes. When grid power demand is low, an electric heater converts excess electricity generated by the steam turbine into thermal energy stored in the silicon-based thermal storage medium. When power demand rises, the silicon-based thermal storage medium releases heat to the thermionic cathode in the middle layer. The thermionic cathode emits thermoelectrons toward the anode, converting some of the thermal energy into electrical output. The remaining heat heats the anode. The steam in the internal tube absorbs the anode's residual heat and is then transported through the drum to the steam turbine for power generation. This unique heat storage and energy conversion method increases the thermal storage temperature and reduces irreversible exergy losses. The thermionic power generation technology enhances the dynamic response of the steam turbine, enabling synergistic and complementary power generation, and improving the efficiency and flexibility of the CFPP. The present invention also constructs relevant energy, exergy and economic models, develops a multi-objective coordinated control method of boiler-generator-storage, and provides theoretical guidance for the design of deep peak-shaving systems for coal-fired units.

[0003] For example, Chinese patent publication number CN115199349B discloses a coal-fired power generation system coupled with steam energy storage and an operating method, and provides the following technical solutions: The present invention provides a coal-fired power generation system coupled with steam energy storage and an operating method, which belongs to the field of coal-fired power generation technology. A coal-fired power generation system coupled with steam energy storage includes: a coal-fired power generation component, the coal-fired power generation component including: a coal-fired boiler, a high-pressure steam turbine, a medium-pressure steam turbine, a low-pressure steam turbine, a condenser, a deaerator, and a high-pressure heater, which are connected and arranged; a steam energy storage component, the steam energy storage component including: a gas storage tank; the coal-fired power generation system coupled with steam energy storage of the present invention improves the peak-shaving and frequency-regulating capabilities of the coal-fired unit. However, the above-mentioned coal-fired power generation system coupled with steam energy storage and its operating method mainly rely on coal-fired boilers and steam gas storage tanks to improve peak-shaving capabilities, but cannot efficiently integrate renewable energy. The energy storage method is limited to steam, and the heat storage density is relatively low, which cannot achieve deep peak-shaving. The response speed is slow, it relies on the adjustment of boiler parameters, the minimum load reduction is limited, and it cannot solve the problem of insufficient utilization of steam latent heat, and the peak-shaving flexibility is insufficient. Summary of the Invention

[0004] The present application solves the problems of limited heat storage temperature, insufficient utilization of steam latent heat, high minimum power load and slow dynamic response speed in the prior art, and proposes a heat storage coal-fired thermal system based on steam cascade power generation, which achieves the purposes of improving heat storage temperature, enhancing peak shaving flexibility, improving response speed and efficiency. By coupling heat electron technology and steam cascade power generation, the cathode of the heat electron device will emit hot electrons to the anode with lower temperature due to the higher temperature, and this process will directly convert part of the heat energy into electric energy output, while the remaining heat energy heats the anode, and the internal steam absorbs the waste heat to generate power efficiently, realizing fast energy conversion and synergistic complementation.

[0005] Further, the silicon-based heat storage layer and the heat electron device arranged coaxially realize high heat storage density and fast heat energy transfer, the heat conversion channel between the cathode and the anode of the heat electron device directly converts part of the heat energy into electric energy, reducing energy loss; at the same time, the anode hot end is connected to the steam pipeline inlet, and the waste heat is used to heat the steam for cascade power generation, which not only improves the response speed, but also enhances the integration capability with renewable energy, effectively solves the problem of insufficient utilization of steam latent heat, and greatly improves the system flexibility and efficiency.

[0006] To achieve the above-mentioned purposes, the present application adopts the following technical solutions: A heat storage coal-fired thermal system based on steam cascade power generation, comprising: A coal-fired unit, comprising a boiler and a turbine module connected to each other and a generator, the turbine module comprising a high-pressure turbine, a medium-pressure turbine and a low-pressure turbine connected in series, and a heat exchanger assembly connected between the boiler and the turbine module; A heat storage power generation device, composed of a silicon-based heat storage layer and a heat electron device arranged coaxially and an electric heater, the silicon-based heat storage layer being wrapped outside the heat electron device, and the electric heater being located outside the silicon-based heat storage layer; the electric heater is connected to the silicon-based heat storage layer through a high-temperature resistant pipeline, and a thermoelectric conversion channel is formed between the cathode and the anode of the heat electron device, and the anode hot end is connected to the steam pipeline inlet.

[0007] The present application integrates the coal-fired unit and the heat storage device, realizes the synergistic complementation of coal-fired power generation and renewable energy, maximizes the utilization of steam heat energy through the cascade design of high-pressure, medium-pressure and low-pressure turbines of the coal-fired unit; the coaxial layout of the heat storage device improves the heat transfer efficiency and reduces heat loss; the thermoelectric channel directly converts electric energy by using the thermionic effect, while the waste heat heats the steam, enhances the dynamic response capability of the system, solves the minimum stable combustion load limitation of the coal-fired power plant during peak shaving, and improves the overall power generation efficiency and flexibility.

[0008] As a preferred, the electric heater is connected with the wind turbine and the solar panel through an intelligent control system, which includes sensors and controllers as well as a power distributor; the sensors monitor the power generation of the wind turbine and the solar panel and the power demand of the electric heater in real time, and the controllers allocate the electric energy through the power distributor based on the sensor data.

[0009] The intelligent control system monitors the renewable energy power generation and heat storage demand in real time, dynamically allocates the electric energy, and the sensor data drives the controller to optimize the power distribution, ensuring efficient storage of excess electric energy when the grid demand is low and avoiding energy waste; the power distributor precisely adjusts the input of the electric heater, improving the heat storage efficiency of the silicon-based heat storage layer and enhancing the system's adaptability to renewable energy fluctuations, thereby improving the economic efficiency and peak regulation stability of the coal-fired power plant.

[0010] As a preferred, the hot electron device has a vacuum environment inside, the electron emission material includes a special metal or alloy with low work function, and the cathode surface is provided with a distributed temperature sensor, and the anode is provided with several temperature sensors in the steam cooling channel; the cathode emits hot electrons to the anode at high temperature, part of the heat energy is directly converted into electric energy output, and the remaining heat energy heats the anode; the water vapor in the internal steam pipeline absorbs the residual heat and is delivered to the turbine module through the steam drum for power generation.

[0011] The vacuum environment and low work function material of the hot electron device promote efficient heat-electricity conversion, the low work function metal or alloy reduces the energy loss of electron emission, and improves the efficiency of heat energy conversion to electric energy; the remaining heat energy is absorbed by steam and delivered to the steam turbine for power generation, realizing the cascade utilization of heat energy and reducing irreversible loss; this mechanism quickly responds to changes in power demand, improves the dynamic response capability of the steam turbine, and solves the problem of insufficient utilization of latent heat in traditional coal-fired systems; the sensors on the cathode monitor the temperature gradient on the cathode surface in real time, identify local hot spots, and the sensors on the anode monitor the steam heat absorption efficiency to optimize waste heat recovery.

[0012] As a preferred, the boiler is provided with a combustion chamber or a heat exchange structure inside, and the boiler is connected with the hot electron device through a heat transfer pipeline to receive heat from the hot electron device to generate steam; the high-pressure turbine, the medium-pressure turbine and the low-pressure turbine are all provided with blade and rotor structures adapted to different pressure steam, the high-pressure turbine is connected with the boiler through a steam pipeline, the medium-pressure turbine is connected with the high-pressure turbine, and the low-pressure turbine is connected with the medium-pressure turbine to convert the heat energy of the steam into mechanical energy.

[0013] The boiler is connected with the heat transfer pipeline of the hot electron device, and the turbine module is adapted to different pressure steam to receive the waste heat of the hot electron device for steam generation, strengthening heat energy recovery; the series structure of high-pressure, medium-pressure and low-pressure turbines optimizes the utilization of steam gradient, and the blade and rotor design is adapted to maximize the mechanical energy conversion efficiency; the thermodynamic efficiency and economy of the coal-fired unit are improved, and deep peak regulation operation is supported at the same time.

[0014] Preferably, the heat exchanger assembly includes a first heat exchanger group and a second heat exchanger group, each of the first heat exchanger group and the second heat exchanger group is provided with a plurality of heat exchangers, and the heat exchangers adopt a plate or shell and tube structure; the medium-pressure turbine and the high-pressure turbine are input to the first heat exchanger group, and the low-pressure turbine is input to the second heat exchanger group, the first heat exchanger group outputs to the boiler, and the second heat exchanger group outputs to the fourth heat exchanger.

[0015] The structured design of the heat exchanger components promotes heat recovery. The first heat exchanger group processes the heat output of the high-pressure turbine, and the second heat exchanger group processes the heat of the low-pressure turbine, realizing graded heat recovery. The plate or shell and tube structure enhances heat exchange efficiency and reduces energy loss. The output to the boiler and the fourth heat exchanger optimizes heat energy reuse and improves the overall energy utilization rate of the system.

[0016] Preferably, the heat exchangers in the first heat exchanger group and the second heat exchanger group are output to the next stage and input to the previous stage in sequence; the previous stage of the first heat exchanger group is the boiler, and the next stage is the fourth heat exchanger; the previous stage of the second heat exchanger group is the fourth heat exchanger, and the next stage is the low-pressure turbine.

[0017] The sequential connection of the heat exchangers optimizes the heat flow path. Heat is input from the upper-level boiler and output from the lower-level fourth heat exchanger or low-pressure turbine, ensuring orderly transfer of heat gradients and reducing entropy increase and irreversible losses. This chain structure improves heat recovery efficiency, supports the flexible operation of coal-fired units, and enhances system stability.

[0018] Preferably, the fourth heat exchanger is connected to a water feed pump through a water pipe, and the water feed pump transports water from an external water source or condensate in the system to parts of the system that need water; the low-pressure turbine is connected to the condenser through a steam pipe, so that the steam discharged from the low-pressure turbine is quickly condensed into water. The condenser includes a cooling water pipe and a condensation chamber. The condensate pump connects the condenser to the end of the second heat exchanger group through a water pipe. The condensate pump extracts the condensate in the condenser and transports it to parts of the system that need water; the condenser adopts a hybrid condenser, which is equipped with an atomizing nozzle inside.

[0019] The design of the feedwater pump and condenser optimizes water circulation and steam condensation. The feedwater pump delivers water or condensate to ensure continuous water supply to the system. The hybrid condenser increases the steam contact area through the atomizing nozzle, accelerates the condensation process, and reduces energy loss. The condensate pump recycles the condensate to the second heat exchanger group, realizing the recycling of water resources and improving the economy and environmental protection of the system.

[0020] Preferably, the intelligent control system includes a three-layer collaborative control architecture, specifically: an intelligent decision-making center, which receives grid load instructions, renewable energy power generation and boiler stable combustion threshold in real time, and generates a thermal electron target power curve and a silicon-based heat storage layer temperature setting value through a dynamic programming algorithm; a thermal electron coordinator, which dynamically calculates the optimal temperature difference between the anode and the cathode based on the electron potential barrier height, and decomposes it into a cathode heating power signal and an anode cooling intensity signal; a distributed execution unit, which adjusts the power supply of the electric heater according to the cathode heating power signal, so that the heat release rate of the silicon-based heat storage layer matches the target value; controls the opening of the steam regulating valve according to the anode cooling intensity signal, optimizes the water vapor flow to cool the anode; and activates the atomizing nozzle for forced cooling when the optimal temperature difference is greater than the set threshold.

[0021] The three-layer collaborative control architecture intelligently adjusts system parameters. The intelligent decision-making center generates optimization curves based on grid demand and renewable energy data to ensure safe peak-shaving of coal-fired units. The thermoelectric coordinator calculates the temperature difference between the anode and cathode to maximize the thermoelectric conversion efficiency. The distributed execution units accurately control heat storage, heat release and steam flow to improve dynamic response capabilities. The atomizing nozzles activate forced cooling to prevent overheating risks and enhance system flexibility and safety.

[0022] Preferably, the silicon-based heat storage layer adopts a silicon heat storage medium composed of silicon-based materials and additives, and is wrapped with insulation material on the outside. The silicon-based heat storage layer is connected to the electric heater through a high-temperature resistant pipe; when the grid demand is low, the electric heater converts electrical energy into thermal energy and efficiently stores it in the silicon-based heat storage layer, and quickly releases heat to the thermionic device when the demand rises.

[0023] The silicon-based thermal storage medium is designed to achieve efficient thermal energy storage and release. Silicon-based materials and additives improve thermal storage density and thermal stability, and thermal insulation materials reduce heat loss. It quickly stores heat when grid demand is low and quickly releases heat when demand rises, supporting the rapid response of thermionic devices. This mechanism breaks through the temperature and pressure limitations of traditional working fluids and improves the peak-shaving flexibility and economy of coal-fired power plants.

[0024] Preferably, the generator is provided with a stator and a rotor structure, and is connected to the low-pressure turbine via a mechanical transmission device to convert the mechanical energy output by the low-pressure turbine into electrical energy.

[0025] The generator's standard design ensures reliable energy conversion. The stator and rotor structure efficiently converts the mechanical energy of the low-pressure turbine into electrical energy, maintaining stable power output. The mechanical transmission device simplifies connections, reduces energy losses, and supports the system's overall power generation efficiency and reliability.

[0026] Compared with the prior art, the present invention has the following beneficial effects.

[0027] 1. This invention achieves high heat storage density and thermal stability through the unique design of a silicon-based thermal storage medium. The external insulation significantly reduces heat loss and raises the upper limit of heat storage temperature. The vacuum environment of the thermionic device and the low-work function special metal alloy promote efficient heat-to-electricity conversion, minimizing energy loss during electron emission. Simultaneously, waste heat from the anode is absorbed by steam for cascade power generation, maximizing thermal energy utilization. This mechanism effectively addresses the problem of insufficient latent heat utilization in conventional steam generation, reduces system entropy increase and irreversible losses, and ensures an efficient and orderly heat transfer path.

[0028] 2. This invention utilizes an intelligent control system to monitor grid load and renewable energy generation in real time, dynamically programming thermionic device power curves and thermal reservoir temperature setpoints to rapidly respond to demand fluctuations. Thermionic device cathodes emit thermal electrons, converting some of the thermal energy directly into electricity. The remaining heat heats steam, enabling synergistic and complementary power generation and significantly improving dynamic response capabilities. The silicon-based thermal reservoir rapidly stores heat when demand is low and releases it quickly when demand is high. Combined with steam control valves to optimize flow, this technology overcomes the minimum stable load constraints of coal-fired units, significantly enhancing peak-shaving flexibility and overall response speed.

[0029] 3. This invention optimizes energy conversion efficiency through a thermoelectric-steam cascade system. The heat exchanger assembly utilizes a high-efficiency plate-type structure for tiered heat recovery, minimizing energy loss and improving heat recovery. Economic efficiency is reflected in water recycling and efficient thermal energy storage, such as condensate recovery by the condensate pump and optimized water supply by the feedwater pump. Safety is ensured by a three-tiered coordinated control architecture. An intelligent decision-making center, combined with dynamic algorithms, ensures safe peak load regulation, while forced cooling of the atomizing nozzles prevents overheating. These features collectively enhance system reliability, cost-effectiveness, and environmental friendliness. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of a heat storage coal-fired thermal system based on steam cascade power generation according to the present invention.

[0031] Figure 2 This is an electron transition diagram of a thermionic device in a heat storage coal-fired thermal system based on steam cascade power generation according to the present invention.

[0032] Figure 3 This is a diagram showing the energy band structure of a thermionic device in a heat storage coal-fired thermal system based on steam cascade power generation according to the present invention.

[0033] Illustration: 1. Wind turbine, 2. Electric heater, 3. Thermionic device, 4. Silicon heat storage medium, 5. Boiler, 6. High-pressure turbine, 7. Medium-pressure turbine, 8. Low-pressure turbine, 9. Heat exchanger 1, 10. Heat exchanger 2, 11. Heat exchanger 3, 12. Heat exchanger 4, 13. Feedwater pump, 14. Heat exchanger 5, 15. Heat exchanger 6, 16. Heat exchanger 7, 17. Heat exchanger 8, 18. Generator, 19. Condenser, 20. Condensate pump, 21. Solar panel, 22. Water vapor. DETAILED DESCRIPTION

[0034] See also Figure 1-Figure 3 As shown, a thermal storage coal-fired thermal system based on steam cascade power generation includes: A coal-fired unit comprising a boiler and a turbine module connected to each other, and a generator, wherein the turbine module comprises a high-pressure turbine, a medium-pressure turbine, and a low-pressure turbine connected in series, and a heat exchanger assembly is further connected between the boiler and the turbine module; The heat storage power generation device consists of a coaxially arranged silicon-based heat storage layer, a thermionic device and an electric heater. The silicon-based heat storage layer is coated on the outside of the thermionic device, and the electric heater is located on the outside of the silicon-based heat storage layer. The electric heater is connected to the silicon-based heat storage layer through a high-temperature resistant pipe. A thermoelectric conversion channel is formed between the cathode and anode of the thermionic device, and the hot end of the anode is connected to the steam pipe inlet.

[0035] This invention proposes a thermal storage-coal-fired thermal system based on a thermionic-steam cascade power generation system. When grid power demand is low, excess electricity generated by the steam turbine is fed to an electric heater for use, heating a silicon-heat storage medium. This medium is also insulated externally, allowing electrical energy to be converted into thermal energy for storage. When power demand increases, the heat stored in the silicon-heat storage medium is released and transferred to the thermionic device. Due to its high temperature, the thermionic device's cathode emits thermal electrons toward the cooler anode. This process converts some of the thermal energy into electrical output, while the remainder heats the anode. Simultaneously, steam from the coal-fired unit absorbs the waste heat from the thermionic anode and is transferred through the steam drum to the steam turbine for power generation. The rapid transient response of the thermionic power generation technology helps improve the dynamic response capability of the coal-fired steam turbine, enabling synergistic and complementary power generation between thermionic devices and the steam turbine, thereby enhancing the power generation efficiency and flexibility of the CFPP.

[0036] like Figure 1 In one embodiment shown, Figure 1This is a schematic diagram of a thermal storage coal-fired thermal system based on steam cascade power generation according to the present invention. The present invention comprises: a renewable energy power generation device comprising a wind turbine 1 and a solar panel 21. The wind turbine comprises a wind turbine capable of efficiently capturing wind energy and converting it into electricity, and a corresponding generator. The solar panel 21 comprises a plurality of photovoltaic cells capable of efficiently converting sunlight into electricity. An electric heater 2, which has sufficient heating power and high power-to-heat conversion efficiency, is connected to the renewable energy power generation device via a power transmission line. The electric heater 2 receives electricity generated by the wind turbine 1 and the solar panel 21 and converts it into heat. A silicon thermal storage medium 4, which possesses specific physical and chemical properties, including high heat storage density, good thermal stability, and thermal conductivity, is connected to the electric heater 2 via a high-temperature-resistant pipe and is used to store the heat generated by the electric heater 2.

[0037] The wind turbine 1 and the solar panel 21 are connected to the electric heater 2 through an intelligent control system. The intelligent control system includes sensors, a controller and a power distributor. The sensors can monitor the power generation of the wind turbine 1 and the solar panel 21 and the power demand of the electric heater 2 in real time. The controller can reasonably distribute electrical energy according to system requirements through the power distributor based on the sensor data.

[0038] The silicon heat storage medium 4 adopts a composite material with high heat storage density and thermal stability. The composite material is composed of a silicon-based material and a specific additive. The additive can enhance the heat storage performance and thermal stability of the silicon-based material. The silicon heat storage medium 4 is wrapped with an insulating material on the outside to reduce heat loss.

[0039] Thermionic device 3 has a special electron emission material and structure that can efficiently convert thermal energy into electrical energy. Due to the high temperature of the cathode of thermionic device 3, it will emit thermal electrons to the anode with a lower temperature. This process will convert part of the thermal energy into electrical energy output, while the remaining thermal energy will heat the anode. The cathode surface is provided with a high-temperature resistant distributed sensor, embedded with a micro tungsten-rhenium thermocouple array, specifically located at the contact surface between the silicon heat storage medium 4 and the cathode, with a grid spacing of 50mm. Temperature sensors are installed in the anode cooling channel, specifically located on the inner wall of the anode steam flow channel, with a group arranged every 200mm. The sensors in this part have a certain pressure resistance.

[0040] At the same time, steam from the coal-fired unit absorbs waste heat from the thermionic anode and is transported to the turbine via the steam drum. Boiler 5 contains a combustion chamber or heat exchange structure capable of efficiently burning fuel or receiving external heat to produce high-temperature, high-pressure steam. Boiler 5 is connected to thermionic device 3 via heat transfer piping, receiving heat from thermionic device 3 to generate steam. High-pressure turbine 6, medium-pressure turbine 7, and low-pressure turbine 8 are connected. High-pressure turbine 6 has blades and rotor structures capable of withstanding the impact of high-pressure steam and efficiently converting it into mechanical energy. Medium-pressure turbine 7 and low-pressure turbine 8 have corresponding structures to accommodate medium- and low-pressure steam, respectively. High-pressure turbine 6 is connected to boiler 5 via steam piping, medium-pressure turbine 7 is connected to high-pressure turbine 6, and low-pressure turbine 8 is connected to medium-pressure turbine 7, converting the thermal energy of steam into mechanical energy.

[0041] The thermionic device 3 has a high thermal-electrical energy conversion efficiency. The electron emission material inside it is a special metal or alloy with a low work function. The thermionic device 3 also has an optimized electrode structure and vacuum environment to promote electron emission and collection.

[0042] Heat exchangers 1 to 8 use high-efficiency plate heat exchangers. The plates of the plate heat exchangers are made of metal materials with high thermal conductivity. The surface of the plates is specially treated to enhance the turbulence of the fluid, thereby enhancing the heat exchange efficiency.

[0043] Generator 18, which has a stator and rotor structure with high power generation efficiency, is connected to low-pressure turbine 8 via a mechanical transmission device and is used to convert the mechanical energy output by low-pressure turbine 8 into electrical energy. Multiple heat exchangers, including heat exchanger 1, heat exchanger 2, heat exchanger 3, heat exchanger 4, heat exchanger 5, heat exchanger 6, heat exchanger 7, and heat exchanger 8, each have a plate or shell-and-tube structure that enables efficient heat exchange. A water feed pump 13, which has sufficient head and flow rate to transport water from an external water source or condensate within the system to areas of the system that need water, is connected to heat exchanger 4 via a water pipe and is used to supply water to the system.

[0044] The condenser 19 and the condensate pump 20, the condenser 19 has a cooling structure that can quickly condense the steam discharged from the low-pressure turbine 8 into water, including a cooling water pipe and a condensation chamber. The condenser 19 is connected to the low-pressure turbine 8 through a steam pipe. The condensate pump 20 has the function of extracting the condensate in the condenser 19 and transporting it to other parts of the system. The condensate pump 20 connects the condenser 19 and the heat exchanger 7 through a water pipe.

[0045] The water supply pump 13 is equipped with a variable frequency speed regulating device, which includes a frequency converter and a control module. The frequency converter can adjust the motor speed of the water supply pump 13 according to the load change of the system, thereby adjusting the water flow.

[0046] The condenser 19 is a hybrid condenser, which is provided with an atomizing nozzle inside, which can atomize the cooling water to increase the contact area with the steam and has efficient steam condensation performance.

[0047] This invention innovatively couples thermionic power generation into a coal-fired power generation cycle to achieve cascaded thermal energy utilization and dynamic complementary power generation. This helps decouple heat storage from the thermodynamic parameters of coal-fired units, thereby improving the safety, flexibility, and economy of the thermal storage-coal-fired unit. Thermionic devices play a key role in the system. They utilize a special metal or alloy with a low work function as the electron emitter material, and feature an optimized electrode structure and vacuum environment. When electricity demand rises, the silicon-heat storage medium releases heat to the thermionic device. Due to the high temperature, the thermionic device's cathode emits thermal electrons toward the anode. This process directly converts some of the thermal energy into electrical output, unlike traditional methods that rely solely on changes in the working fluid's temperature and pressure to drive mechanical components, such as steam turbines, to generate electricity. This energy conversion method based on electron emission and collection is relatively independent of the conventional working fluid's thermodynamic cycle, reducing its dependence on traditional working fluid temperature and pressure parameters. For example, in traditional coal-fired power generation, steam temperature and pressure must be strictly controlled within a certain range to ensure efficient and stable turbine operation. Thermionic power generation overcomes this limitation to a certain extent.

[0048] When grid power demand is low, the system converts excess electricity generated by the steam turbine into thermal energy stored in a silicon-based thermal storage medium through an electric heater. Silicon-based thermal storage mediums have high heat storage density, excellent thermal stability, and thermal conductivity. Their heat storage process is independent of the temperature and pressure fluctuations of conventional working fluids that limit energy storage. When power demand rises, the silicon-based thermal storage medium rapidly releases heat to the thermionic device, which responds quickly and converts the heat into electrical output while simultaneously heating the anode. Water vapor in the internal tube absorbs the anode's excess heat and is then transferred through the drum to the steam turbine for power generation. This heat storage and energy release method enables the system to rapidly adjust energy output in response to fluctuations in power demand, bypassing the limitations of the slow temperature and pressure increase of the working fluid in conventional power generation systems and improving the system's rapid response capabilities. For example, while molten salt thermal storage technology can store thermal energy, it still faces challenges such as insufficient utilization of steam latent heat when integrated with coal-fired power generation systems. This system's heat storage and energy release mechanism effectively addresses these issues, enhancing the system's flexibility and responsiveness.

[0049] Within this framework, the present invention constructs an energy, exergy, and economic model for a thermal storage-coal-fired thermal system based on a thermoelectric-steam cascade power generation system to reveal the system's dynamic response mechanism and energy quality loss patterns. Furthermore, a multi-objective coordinated control method for the boiler-generator-storage system was developed, balancing unit flexibility, economy, and safety. This method provides theoretical guidance for the design of deep peak-shaving systems for coal-fired units.

[0050] like Figure 2 In one embodiment shown, Figure 2 This diagram shows the electronic transitions of thermionic devices in a thermal storage and coal-fired thermal system based on steam cascade power generation according to the present invention. The cathode of thermionic devices emits thermal electrons toward the anode, converting some of the thermal energy into electrical output. The remaining heat heats the anode. Water vapor in the internal tube absorbs the residual heat from the anode and is then transported through the steam drum to the steam turbine for power generation.

[0051] like Figure 3 In one embodiment shown, Figure 3 This diagram shows the energy band structure of a thermionic device in a thermal energy storage and coal-fired thermal system based on steam cascade power generation according to the present invention. The left side of the diagram represents the cathode n-type semiconductor, and the right side represents the anode p-type semiconductor. The center portion represents the PN junction depletion region. EF and EF' represent the Fermi levels of the cathode and anode, respectively. The Fermi level is the highest energy level occupied by electrons at absolute zero.

[0052] φc and φa represent the work functions of the cathode and anode, respectively, i.e., the energy required for an electron to escape from the Fermi level to the vacuum level. EVac and E'Vac represent the affinities of the cathode and anode, respectively, i.e., the energy required for an electron to escape from the bottom of the conduction band to the vacuum level. eVTI represents the threshold energy for thermionic emission, i.e., the minimum energy required for an electron to be emitted from the cathode to the anode. φm represents the electron barrier height, i.e., the energy barrier that an electron must overcome to travel from the cathode to the anode.

[0053] The intelligent control system comprises a three-layer collaborative control architecture. Specifically, the intelligent decision-making center, serving as the top-level module of the control system, is responsible for global optimization and strategy generation. It is deeply integrated with the intelligent control system, which includes sensors, controllers, and power distributors, to enable data-driven, real-time decision-making.

[0054] Its core functions are: 1. Data reception and processing Three key input signals are collected in real time: grid load instructions, which come from the grid dispatching system and indicate current and predicted power demand; renewable energy power generation, which comes from wind turbines and solar panels, and monitors instantaneous power fluctuations through sensors; and boiler stable combustion threshold, which comes from the coal-fired unit monitoring system, to ensure that the boiler operates above the minimum stable combustion load to avoid the risk of flameout.

[0055] These data are transmitted to the central processor via a high-speed communication network for filtering, normalization and fusion processing to eliminate noise interference.

[0056] 2. Target value generation: Based on the fused data, two key setpoints are generated: the thermal electron target power curve, which calculates the power output that the thermal electron needs to supplement based on grid load gaps and renewable energy fluctuations. For example, a higher proportion will be allocated when there is a sudden increase in load.

[0057] The silicon-thermal storage medium temperature set point is optimized within the temperature range, in this embodiment, of approximately 1200–1400 K, in combination with the thermal stability and thermal conductivity of the thermal storage medium, to ensure efficient thermal energy storage and release.

[0058] The generation process uses a dynamic programming algorithm to balance efficiency, safety and economy, and outputs instructions to the thermal electron coordinator.

[0059] The intelligent decision-making center utilizes a multi-objective coordinated control method for boilers, generators, and storage units to decouple renewable energy from coal-fired units. In one embodiment, when wind power output suddenly drops, sensors detect the power shortfall. The controller calculates the required thermal electronic compensation power of 6MW. The power distributor then adjusts the power supply priority of the electric heaters to ensure that the silicon-thermal storage medium quickly heats up to the target value. This process has a response time of less than 200ms, significantly improving system flexibility.

[0060] The hardware in this part is deployed in the central control room, integrated with a high-reliability industrial PLC, and issues instructions through the OPC UA protocol.

[0061] As an intermediate module, the thermoelectric coordinator focuses on optimizing the energy conversion of thermoelectric devices. It receives instructions from the intelligent decision-making center and dynamically adjusts the temperature difference between the cathode and anode based on the principle of thermoelectric emission to ensure efficient thermoelectric conversion. Figure 2 .

[0062] Its core functions are: The temperature difference between the cathode and anode is dynamically calculated using the principle of thermal electron emission, i.e., the cathode emits electrons at high temperature to the anode at low temperature, and the optimal temperature difference ΔT is solved in real time. The lower limit of the temperature difference is set with reference to the electron barrier height φm. In this embodiment, the minimum value of ΔT is equal to φm divided by k times logP to ensure effective electron emission. This part can be referred to in the attached Figure 3 .

[0063] Then, an optimization goal is set to maintain ΔT within the range of 400K±50K to maximize the thermoelectric conversion efficiency. The calculation process is embedded in a fuzzy logic controller to adapt to load changes, for example, automatic adjustments can be made when the grid demand fluctuates.

[0064] Command decomposition and signal generation: decomposing the temperature difference command into two-way control signals, including: The cathode heating power signal adjusts the output of the electric heater and controls the heat release rate of the silicon-heat storage medium to stabilize the cathode temperature at 1350K±30K.

[0065] The anode cooling intensity signal controls the steam regulating valve opening, adjusts the water vapor flow to cool the anode, and maintains a temperature difference safety threshold. In this embodiment, it triggers protection when it exceeds 600K.

[0066] Signal generation is based on feedforward-feedback composite control to anticipate the impact of thermal inertia and avoid overshoot.

[0067] The thermionic cathode, due to its high temperature, emits thermal electrons toward the cooler anode. This process converts some of the thermal energy into electrical output, while the remainder heats the anode. Simultaneously, steam from the coal-fired unit absorbs the waste heat from the thermionic anode and is transported through the steam drum to the turbine.

[0068] The thermoelectric coordinator implements closed-loop regulation through a controller. In this embodiment, when power demand increases, it receives a 5MW power command from the decision-making center, invokes the temperature difference model, outputs ΔT = 420K, and then decomposes the command to increase the cathode heating power by 35% and the anode steam flow by 23%. This process reduces the steam turbine response delay from several minutes with traditional technology to less than one minute with the present invention.

[0069] This part uses a dedicated microprocessor, and in this embodiment, the ARM Cortex series is used, which integrates a temperature sensor network. The algorithm layer uses multi-objective optimization to avoid over-temperature damage to the electrode material.

[0070] As the underlying module, the distributed execution unit is responsible for accurately executing the instructions of the thermal electronic coordinator and linking key equipment to achieve rapid response. It seamlessly cooperates with the actuator of the intelligent control system to ensure system stability and safety.

[0071] Its core functions are: The equipment is linked and executed to control three key devices: The electric heater adjusts the power supply of the electric heater 2 through the power distributor based on the cathode heating power signal to achieve rapid heating or cooling of the silicon-heat storage medium.

[0072] The steam regulating valve adjusts the valve opening according to the anode cooling intensity signal, regulates the water vapor flow, and optimizes heat recovery.

[0073] The emergency cooling device is activated. When the temperature difference exceeds the limit, such as ΔT>600K or the sensor alarm occurs, the micro-spray device is started to force cooling of the anode to prevent material failure.

[0074] The execution unit adopts a distributed architecture, each device responds to instructions independently and receives signals through high-speed I / O modules. The electric heater adopts variable frequency drive, and the steam regulating valve adopts proportional integral control to stabilize steam parameters. Emergency cooling is linked with the atomizing nozzle of condenser 19 to increase the cooling contact area.

[0075] In the scenario of a sudden increase in grid load, the execution unit completes the action in a very short time and outputs the target power.

[0076] This hardware utilizes redundant actuators, including electric valves and solid-state relays, deployed on-site. The software integrates a fault diagnosis module, providing real-time status feedback to the intelligent decision-making center, creating a closed-loop control system. Direct connectivity to the sensor network ensures synchronization of execution and monitoring.

[0077] The present invention realizes a dynamic temperature difference synergy mechanism and establishes a temperature difference-power conversion efficiency model based on the energy band structure of thermionic devices: When the temperature difference between the cathode and anode is less than the potential barrier threshold, the cathode temperature is automatically increased or the anode cooling is enhanced; When the temperature difference exceeds the safety limit, such as 600K, the anode spray cooling is started to protect the electrode material; When the grid load fluctuates, the temperature difference is dynamically adjusted to the most efficient range of 400K±50K.

[0078] The present invention can maximize thermoelectric efficiency, adjust the heat release rate of the silicon-heat storage medium according to real-time power demand, maintain the cathode temperature at 1350K±30K; and minimize steam delay, adjust the anode steam flow in advance through feedforward control, and shorten the steam turbine response time.

[0079] The sensor collects three key data in real time: the fluctuation of renewable energy power generation, the actual power demand of the electric heater, and the surface temperature distribution of the anode and cathode with an accuracy of ±0.5K. The central controller integrates and processes these data to generate coordinated instructions.

[0080] When the grid load suddenly increases, new energy electricity is allocated to the electric heater to increase the cathode temperature to the target value within seconds; when the output of renewable energy drops sharply, the power allocation of the electric heater is reduced, and the heat storage medium is started to release heat to compensate for the power gap; when the boiler is close to the stable combustion limit, a steam turbine load reduction warning is sent to increase the proportion of thermal electron power generation.

[0081] When the intelligent control system detects a temperature anomaly, it will take some or all of the following measures: immediately cut off the power supply to the electric heater; activate the anode spray cooling device; and switch to the steam turbine backup control mode.

[0082] In one embodiment, when wind power output fluctuations cause a 10MW grid shortage, the decision-making layer calculates that thermionic devices are required to fill the 6MW gap, setting the cathode target temperature to 1370K and the temperature difference to 430K; the coordination layer instructs the electric heater power to increase to 120% of the rated value and adjusts the steam valve opening to 75% to enhance anode cooling; the silicon-heat storage medium of the execution layer releases the stored heat to heat the cathode, and the thermionic power generation power output is stabilized at 6.2MW.

[0083] The present invention is not limited to the above-mentioned embodiments. Regardless of any changes in shape or material composition, any structural design provided by the present invention is a variation of the present invention and should be considered within the scope of protection of the present invention.

Claims

1. A thermal storage coal-fired thermal system based on steam cascade power generation, characterized in that: include: A coal-fired unit comprising a boiler (5) and a turbine module connected to each other and a generator (18), wherein the turbine module comprises a high-pressure turbine (6), a medium-pressure turbine (7) and a low-pressure turbine (8) connected in series, and a heat exchanger assembly is further connected between the boiler (5) and the turbine module; The heat storage power generation device is composed of a coaxially arranged silicon-based heat storage layer, a thermionic device (3), and an electric heater (2), wherein the silicon-based heat storage layer is coated on the outside of the thermionic device (3), and the electric heater (2) is located on the outside of the silicon-based heat storage layer; the electric heater (2) is connected to the silicon-based heat storage layer through a high-temperature resistant pipe, a thermoelectric conversion channel is formed between the cathode and anode of the thermionic device (3), and the hot end of the anode is connected to the steam pipe inlet.

2. The thermal storage coal-fired thermal system based on steam cascade power generation according to claim 1, characterized in that: The electric heater (2) is connected to the wind turbine (1) and the solar panel (21) via an intelligent control system, wherein the intelligent control system comprises a sensor, a controller, and a power distributor; the sensor monitors the power generated by the wind turbine (1) and the solar panel (21) and the power demand of the electric heater (2) in real time, and the controller distributes electric energy via the power distributor based on the sensor data.

3. A thermal storage coal-fired thermal system based on steam cascade power generation according to claim 1 or 2, characterized in that: The thermionic device (3) has a vacuum environment inside, the electron emission material contains a special metal or alloy with low work function, a distributed temperature sensor is provided on the cathode surface, and a plurality of temperature sensors are provided in the steam cooling channel of the anode. The cathode emits thermal electrons to the anode at high temperature, and part of the heat energy is directly converted into electrical energy output. The remaining heat energy heats the anode, and the water vapor in the internal steam pipe absorbs the waste heat and is transported to the turbine module through the steam drum to generate electricity.

4. The thermal storage coal-fired thermal system based on steam cascade power generation according to claim 3, characterized in that: The boiler (5) is provided with a combustion chamber or a heat exchange structure inside. The boiler (5) is connected to the thermistor (3) through a heat transfer pipe, receives heat from the thermistor (3) and generates steam. The high-pressure turbine (6), the medium-pressure turbine (7) and the low-pressure turbine (8) are all provided with blades and rotor structures adapted to steam of different pressures. The high-pressure turbine (6) is connected to the boiler (5) through a steam pipe, the medium-pressure turbine (7) is connected to the high-pressure turbine (6), and the low-pressure turbine (8) is connected to the medium-pressure turbine (7), so as to convert the thermal energy of the steam into mechanical energy.

5. The thermal storage coal-fired thermal system based on steam cascade power generation according to claim 4, characterized in that: The heat exchanger assembly includes a first heat exchanger group and a second heat exchanger group. The first heat exchanger group and the second heat exchanger group are both provided with a plurality of heat exchangers, and the heat exchangers adopt a plate or shell and tube structure. The medium-pressure turbine (7) and the high-pressure turbine (6) are input to the first heat exchanger group, and the low-pressure turbine (8) is input to the second heat exchanger group. The first heat exchanger group outputs to the boiler (5), and the second heat exchanger group outputs to the fourth heat exchanger.

6. The thermal storage coal-fired thermal system based on steam cascade power generation according to claim 5, characterized in that: The heat exchangers in the first heat exchanger group and the second heat exchanger group are output to the next stage and input to the previous stage in sequence; the previous stage of the first heat exchanger group is the boiler (5), and the next stage is the fourth heat exchanger; the previous stage of the second heat exchanger group is the fourth heat exchanger, and the next stage is the low-pressure turbine (8).

7. The thermal storage coal-fired thermal system based on steam cascade power generation according to claim 6, characterized in that: The fourth heat exchanger is connected to a water supply pump (13) through a water pipe, and the water supply pump (13) transports water from an external water source or condensed water in the system to a part of the system that needs water; the low-pressure turbine (8) is connected to a condenser (19) through a steam pipe, so that the steam discharged from the low-pressure turbine (8) is quickly condensed into water, and the condenser (19) includes a cooling water pipe and a condensation chamber. The condensate pump (20) is connected to the condenser (19) and the end of the second heat exchanger group through a water pipe, and the condensate pump (20) extracts the condensed water in the condenser (19) and transports it to a part of the system that needs water; the condenser (19) adopts a hybrid condenser, and an atomizing nozzle is arranged inside it.

8. The thermal storage coal-fired thermal system based on steam cascade power generation according to claim 2, characterized in that: The intelligent control system includes a three-layer collaborative control architecture, specifically: The intelligent decision-making center receives real-time grid load instructions, renewable energy power generation, and boiler stable combustion thresholds, and generates the thermionic device target power curve and silicon-based heat storage layer temperature setpoint through a dynamic programming algorithm; Thermionic coordinator dynamically calculates the optimal temperature difference between cathode and anode based on the electron barrier height and decomposes it into cathode heating power signal and anode cooling intensity signal; The distributed execution unit adjusts the power supply of the electric heater according to the cathode heating power signal, so that the heat release rate of the silicon-based heat storage layer matches the target value; controls the opening of the steam regulating valve according to the anode cooling intensity signal, optimizes the water vapor flow to cool the anode; and activates the atomizing nozzle for forced cooling when the optimal temperature difference is greater than the set threshold.

9. A thermal storage coal-fired thermal system based on steam cascade power generation according to claim 7 or 8, characterized in that: The silicon-based heat storage layer uses a silicon heat storage medium (4) composed of silicon-based materials and additives, and is wrapped with a heat insulation material on the outside. The silicon-based heat storage layer is connected to the electric heater (2) through a high-temperature resistant pipe; when the grid demand is low, the electric heater (2) converts electrical energy into heat energy and efficiently stores it in the silicon-based heat storage layer, and quickly releases heat to the thermal electron device (3) when the demand increases.

10. The thermal storage coal-fired thermal system based on steam cascade power generation according to claim 9, characterized in that: The generator (18) is provided with a stator and a rotor structure, and is connected to the low-pressure turbine (8) through a mechanical transmission device to convert the mechanical energy output by the low-pressure turbine (8) into electrical energy.

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