A multi-stage heat storage system and an intelligent dynamic regulation method thereof

Abstract

The present application belongs to the technical field of heat storage, and particularly relates to a multi-stage heat storage system and an intelligent dynamic regulation method thereof. The multi-stage heat storage system comprises at least three heat storage units, each of which adopts different heat transfer materials and structural features to form a melting point gradient distribution; the heat storage units are connected in series to form an overall heat storage system; the heat storage system comprises an intelligent dynamic regulation device which independently and cooperatively regulates each heat storage unit. Through the gradient functionalization design of solid waste-based composite materials and the synergistic effect of the intelligent dynamic regulation system, the present application not only solves the problems of heat storage and rapid response in high-temperature areas, but also realizes accurate management and efficient utilization of heat energy, thereby providing a new solution for building energy saving and energy management.

Description

Technical Field

[0001] This invention belongs to the field of thermal energy storage technology, and in particular relates to a multi-stage thermal energy storage system and its intelligent dynamic control method. Background Technology

[0002] In the field of building materials and energy utilization, phase change materials (PCMs) have been widely studied and applied as a highly efficient energy storage technology to improve energy utilization efficiency and building energy-saving performance.

[0003] There are numerous research reports on phase change materials in the existing technology: for example, a multifunctional foamed ceramic sound insulation and heat insulation material for building has been disclosed in the existing technology. By introducing components such as phase change microcapsules, it has achieved the dual effects of heat insulation and sound insulation. However, it has limitations in terms of heat storage and rapid response capabilities in high-temperature areas.

[0004] Another existing technology focuses on the preparation of self-insulating mortar, which constructs a multi-layer insulation structure through materials such as gradient graphene aerogel skeleton. Although it improves the insulation effect, it lacks an intelligent mechanism for dynamic regulation of thermal energy, especially the precise control of thermal energy storage and release in different temperature regions.

[0005] While the aforementioned existing technologies have solved the problems of building insulation and energy storage to some extent, they have failed to fully consider the efficient storage and intelligent dynamic control of thermal energy, especially thermal energy management within a multi-level temperature range. Summary of the Invention

[0006] To address the shortcomings of the existing technologies, this invention proposes a multi-stage thermal energy storage system and its intelligent dynamic control method. The aim is to achieve efficient storage and intelligent release of thermal energy by designing a composite phase change thermal energy storage body with a melting point gradient distribution and combining it with intelligent control logic, so as to meet the thermal energy management under different temperature requirements, thereby improving energy utilization efficiency and building energy-saving performance.

[0007] The core innovation of this invention lies in the synergistic effect of the gradient functionalization design of solid waste-based composite materials and the intelligent dynamic control system, which not only solves the problem of thermal energy storage and rapid response in high-temperature areas, but also realizes the precise management and efficient utilization of thermal energy, providing a new solution for building energy conservation and energy management.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A multi-stage thermal energy storage system based on solid waste-based gradient phase change composite material includes a thermal energy storage body composed of at least three concentric tubes, which are arranged from the inside to the outside as an inner layer, a middle layer, and an outer layer. Each layer adopts different heat transfer materials and structural features to form a melting point gradient distribution. The layers are connected in series to form an overall energy storage unit. Each energy storage unit is connected to an independent heating device, and the start and stop of the heating device can be adjusted at any time according to demand.

[0009] Preferably, the thermal storage system is a three-stage thermal storage unit, which is a thermal storage body composed of three concentric tubes, including an inner layer, a middle layer and an outer layer from the inside to the outside.

[0010] The thermal storage system of the present invention has the following technical improvements compared with the prior art: Existing technology: Traditional thermal storage systems often use a centralized heat source to heat all thermal storage units uniformly, which makes it impossible to manage the energy input of different temperature zones within the system independently and precisely.

[0011] Technical improvements of this invention: Structurally, each of the inner, middle, and outer energy storage units is equipped with independent heating equipment (for example, the inner layer is connected to an electric heating rod or a high-temperature hot fluid circuit, while the middle and outer layers are connected to medium- and low-temperature hot fluid circuits). These devices can be started, stopped, and have their power adjusted independently.

[0012] In terms of control: "Targeted energy supply" is achieved. The controller can determine which unit to heat and the amount of heating power based on the actual temperature of each unit, the heat storage status, and user needs.

[0013] Beneficial effects: Solving the problem of unbalanced heat storage: During the system's heat storage phase, energy can be replenished first to the unit that releases the most heat and has the lowest temperature, ensuring that the entire system quickly and evenly returns to its optimal heat storage state, thus avoiding the inefficiency of "some units overheating and some units not being fully filled" in traditional systems.

[0014] Improved initial investment efficiency: When dealing with fluctuating heat sources (such as solar energy), there is no need to oversize the entire system to match peak heat. Only heating equipment that matches the average power needs to be configured, and specific units can be supplemented with auxiliary heating through independent equipment when needed, thereby reducing the initial investment cost of the heating station (example data shows a reduction of 20-30%).

[0015] Energy-saving operation: It avoids the huge energy waste caused by heating the entire system to meet local needs, and realizes "heating on demand" to minimize energy waste during operation.

[0016] Preferably, the heat transfer material of the inner layer includes a skeleton material and an energy storage medium material. The skeleton material includes a high thermal conductivity solid waste-based inorganic non-metallic composite material, and the energy storage medium material includes NaNO3 microcapsules. The skeleton material of the inner layer adopts a hierarchical porous structure or a granular structure.

[0017] Preferably, the inner layer adopts a hierarchical porous structure or a granular structure, and the solid waste filling the inner layer is one or more of fly ash, tailings, coal gangue, slag, and blast furnace slag. Preferably, the granular structure is a spherical or ellipsoidal granular structure.

[0018] "Hierarchical porous or granular structure" mainly refers to the solid waste-based high thermal conductivity skeleton (such as fly ash modified magnesia refractory bricks) that constitutes the inner thermal storage unit. This structural design aims to maximize specific surface area and optimize heat transfer paths.

[0019] Hierarchical porous structures refer to structures with multi-scale pores ranging from nanometers and micrometers to millimeters within their framework. Macropores serve as "warehouses" for energy storage media and fluid channels, while micro- and nanopores enhance media distribution and interfacial contact through capillary action.

[0020] Granular structure (spherical or ellipsoidal): This refers to filling the aforementioned framework material into regular granules. This structure helps reduce fluid resistance, makes the distribution of heat fluid more uniform, and prevents structural stress concentration caused by volume changes in the phase change material.

[0021] The framework material and the energy storage medium (NaNO3 microcapsules) are combined through a "wetting-adsorption" process.

[0022] Pretreatment: First, a solid waste matrix framework with a hierarchical porous or granular structure is prepared.

[0023] Loading: Under vacuum or pressurized conditions, molten NaNO3 phase change material or prepared NaNO3 microcapsule suspension is forcibly impregnated into the pores of the framework.

[0024] Formation: Through capillary forces and surface adsorption, the phase change material is firmly locked within the porous network of the framework, forming a stable composite phase change thermal storage body. This combination method effectively solves the problems of leakage and poor thermal conductivity of pure phase change materials.

[0025] The high thermal conductivity solid waste-based inorganic non-metallic composite material includes filled solid waste, which is selected from one or more of fly ash, tailings, coal gangue, slag and blast furnace slag; the granular structure is spherical or ellipsoidal; the NaNO3 microcapsules are formed by physical methods (such as spray drying) and then loaded onto the solid waste skeleton.

[0026] Compared with existing technologies, the heat transfer materials and structural features of the inner, middle, and outer layers have the following technological improvements and beneficial effects: Existing technologies: Phase change composite materials are mostly filled with monolithic blocks or simple powders, which have problems such as limited heat transfer area, high fluid resistance, easy pulverization, and difficulty in filling.

[0027] Technical improvements of this invention: Granular structure: Specifically refers to the composite of the inner layer of "solid waste-based high thermal conductivity framework and NaNO3 microcapsules" being manufactured into regular spherical or ellipsoidal particles. This not only includes the framework itself being granular, but also means that the final composite thermal storage material product is granular.

[0028] Multi-layer collaborative design: The inner layer (particles), middle layer (porous ceramic bricks), and outer layer (porous composite materials) all adopt a composite mode of "high thermal conductivity porous skeleton + shaped phase change medium". However, the skeleton material and phase change medium of each layer are specially and gradiently designed according to their temperature range.

[0029] Beneficial effects: Significantly increases heat transfer area: After the spherical / ellipsoidal particles are stacked, a regular and huge heat transfer surface is formed, which significantly enhances the heat exchange efficiency between the heat storage body and the flowing hot fluid.

[0030] Reduced flow resistance: The flow channel characteristics of a well-structured particle bed are superior to those of irregular powders or complex porous bodies, which reduces the power consumption of the system's circulating pump.

[0031] Engineering-friendly: The granular material is easy to fill and replace, making it particularly suitable for the production and maintenance of large-scale thermal storage devices. Combined with the gradient material design of each layer, the thermal storage density of the entire system is increased by 30-40%, and the mechanical stability and cycle life (>10,000 cycles) are far superior to traditional single-material systems.

[0032] Preferably, the skeleton material of the intermediate layer is a solid waste ceramic brick loaded with LiCl microcapsules; the preparation method is as follows: using solid waste (such as tailings and slag) as the main raw material, a porous solid waste ceramic is made by sintering; in order to enhance its thermal conductivity and mechanical properties, short-cut silicon carbide fibers are added to the ceramic body as reinforcement during the preparation process, and finally a fiber-reinforced porous solid waste ceramic brick is formed; then, LiCl microcapsules prepared by physical methods (such as spray drying) are loaded into the pores of the porous ceramic brick by vacuum impregnation process.

[0033] LiCl microcapsules are pre-prepared as microcapsules using physical methods (such as spray drying or condensation), and then fixed onto the pores or surface of solid waste ceramic bricks through an "embedding-loading" method. The process of preparing LiCl microcapsules involves encapsulating the LiCl phase change core material with a wall material (such as a gelatin-gum arabic composite wall material) using a physical method (rather than chemical polymerization), forming micron-sized capsules. The solid waste ceramic bricks act as a macroscopic, mechanically strong "carrier skeleton." During preparation, the LiCl microcapsules are mixed with ceramic slurry, then molded and sintered to ensure the microcapsules are uniformly distributed within the ceramic brick. Therefore, LiCl is not directly encapsulated within the original solid waste particles; rather, LiCl is first made into microcapsules and then composited with the solid waste-based ceramic matrix.

[0034] Preferably, the outer heat transfer material uses a graphene / solid waste-based porous composite material as the substrate and paraffin wax as the energy storage medium; the graphene / solid waste-based porous composite material is a porous material prepared by modifying solid waste material with graphene, nano-zirconia, nano-titanium dioxide and carbon nanotubes; the paraffin wax is stored in a vacuum-insulated container.

[0035] The composition by weight is as follows: 70-85 parts solid waste material, 5-10 parts graphene, 3-8 parts nano-zirconia, 2-5 parts nano-titanium dioxide, and 1-3 parts carbon nanotubes. The solid waste material is mainly fly ash, serving as the primary thermal reinforcement; nano-zirconia (ZrO2) improves the heat resistance and structural stability of the framework; nano-titanium dioxide (TiO2) provides auxiliary reinforcement and certain photothermal conversion potential; and carbon nanotubes (CNTs), in synergy with graphene, construct a three-dimensional thermally conductive network, filling the contact thermal resistance between graphene sheets.

[0036] The preparation method of the outer heat transfer material includes the following steps: Raw material pretreatment: Solid waste materials are ball-milled to a particle size D50 < 10 μm. Graphene and carbon nanotubes are ultrasonically dispersed in the presence of a dispersant (such as polyvinylpyrrolidone, PVP) to form a stable suspension.

[0037] Wet mixing: The treated solid waste material, nano-zirconia, nano-titanium dioxide and graphene / carbon nanotube suspension are thoroughly mixed and stirred by a high-speed shear emulsifier to ensure uniform dispersion of each component.

[0038] Molding and foaming: Add foaming agent (such as hydrogen peroxide, H2O2, the amount added is 1-3% of the total mass of the slurry) and foam stabilizer (such as CMC, 0.5-1%) to the mixed slurry, and pour it into the mold.

[0039] Drying and sintering: First, the material is dried and shaped at 80-120℃, and then sintered at 1000-1200℃ under an inert atmosphere. During this process, solid waste particles and nanoparticles combine through solid-phase reaction, while the foaming agent decomposes to form a porous structure, ultimately yielding a graphene / solid waste-based porous composite material with high porosity (>70%) and a three-dimensional interpenetrating network.

[0040] Medium filling: Finally, the paraffin phase change material is filled into the graphene / solid waste-based porous composite material by vacuum impregnation.

[0041] Preferably, the inner heat transfer backbone structure is an integrated multi-layer heat exchanger, while the middle and outer layers both adopt cylindrical vertical bag-shaped single-layer heat exchangers. The inner, middle, and outer layers are each equipped with independent valves to regulate the flow rate, so as to meet the heat power requirements of different operating conditions, and to realize the periodic charging and discharging of the phase change material and the step adjustment of the phase change temperature. Temperature measuring points are set in the inner, middle, and outer layers to monitor the temperature of each part in real time and feed it back to the central controller.

[0042] Preferably, the thermal storage system has an intelligent dynamic control device, including an adjustable heat flux valve connected to each energy storage unit, a temperature sensor installed inside each energy storage unit, and an external controller, which can adjust the opening of the heat flux valve and the temperature sensor of each energy storage unit according to actual needs.

[0043] The thermal storage system is equipped with an intelligent dynamic control device, which consists of three parts: an actuator, a sensor, and a control center. Its connection to the three-stage thermal storage units—inner, middle, and outer layers—is as follows: Actuating component: Adjustable heat flux valve system; Each thermal storage unit—inner, middle, and outer layers—is connected to an independent set of precisely adjustable heat flux valves at its inlet and / or outlet, forming a valve control system. These valves act as actuators, directly controlling the flow rate of the hot fluid entering or leaving each thermal storage unit, thereby regulating the unit's heat storage / release power. Sensing components: Temperature sensor network; Temperature sensors are installed at key locations inside each thermal storage unit to monitor the actual temperature of each unit in real time and continuously. Control center: Central controller; A unified central controller is set up outside the system; All temperature sensors transmit monitoring data to the central controller in real time via signal lines. The central controller performs calculations based on built-in intelligent dynamic control algorithms (such as thermal coupling mapping model and adaptive similarity law), and then sends control commands to each heat flux valve to adjust its opening degree.

[0044] The connection relationships can be summarized as follows: Temperature sensor (data acquisition) → Central controller (processing and decision-making) → Heat flux valve (action execution); this is a typical three-level closed-loop control system that achieves independent yet coordinated precise control of each thermal storage unit. Here, "coordination" means that the central controller, based on a unified thermal coupling mapping model, comprehensively considers the state (temperature, heat storage) of all thermal storage units and their inter-unit thermal influence relationships during decision-making, generating and issuing coordinated control commands to ensure that the actions of each unit cooperate to achieve the overall system operation goals (such as stable output target power, maximum energy efficiency), rather than controlling each unit in isolation.

[0045] Compared with existing technologies, the intelligent dynamic control device has the following technological improvements and beneficial effects: Existing technologies: The control methods are simple, mostly based on switching control at a single temperature point or fixed time program control, which cannot cope with complex and ever-changing heat demands.

[0046] Technical improvements of this invention: Sensing layer: Temperature sensors are installed inside each energy storage unit to form a distributed sensing network, which can acquire detailed thermal state maps of the system in real time.

[0047] Execution layer: Each unit is equipped with a heat flux valve with precisely adjustable opening (instead of a conventional on / off valve) to achieve stepless control of heat flow.

[0048] Decision-making layer: The central controller acts as the sole brain, receiving data from all sensors and making intelligent decisions based on the thermal coupling mapping model (a mathematical model that can describe the thermal interactions between units), and issuing coordinated control commands to all valves.

[0049] Beneficial effects: Precise control: Temperature control accuracy can reach within ±2℃, meeting the stringent requirements of high-end technology and comfortable heating.

[0050] Global optimization: The controller can "sense" the thermal impact between units. For example, when the inner layer heat dissipation is activated, the model will predict the impact on the middle layer and fine-tune the middle layer valve in advance, playing a role in "peak shaving and valley filling" and improving the energy utilization efficiency of the entire system (measured to over 88%).

[0051] High reliability: The structure of distributed sensing and centralized decision-making avoids the problem of improper coordination among multiple controllers, making the system more stable.

[0052] A smart dynamic control method for a multi-stage thermal storage system based on solid waste-based gradient phase change composite materials, as described above, is proposed. Based on user needs and energy requirements under different operating conditions, it uses temperature sensors and controllers to independently adjust the temperature of each energy storage unit using a thermal coupling mapping model, thereby achieving intelligent dynamic control of the entire thermal storage system.

[0053] As a preferred option, a response rate enhancement mechanism is also included. This mechanism can predict the heat storage capacity of the inner high-temperature zone based on actual demand. If the demand is high, the energy supply to the inner high-temperature zone will be prioritized, and then the supply will gradually expand to the middle and outer layers. If the demand is low, the supply will skip the inner high-temperature zone and proceed directly to the middle and outer layers.

[0054] Compared with existing technologies, the above-mentioned intelligent dynamic control method has the following technical improvements and beneficial effects: Existing technology: The system has a fixed heat release path. Regardless of the demand, heat is released sequentially starting from the high-temperature zone, resulting in a "waste of high-quality thermal energy".

[0055] Technical improvements of this invention: After receiving the heating demand, the central controller first determines the required power and temperature levels.

[0056] Small demand determination: If the required temperature is lower than the middle layer phase change temperature (e.g., <80℃) and the required power is low, the controller will "skip the inner high temperature zone" in the decision logic and directly open the valves of the middle layer and / or the outer layer to supply energy.

[0057] Beneficial effects: Energy grade matching: This avoids the "waste of resources" of using high-temperature heat energy in low-temperature applications, effectively improving the system's efficiency (effective energy efficiency). This is similar to using a high flame to boil water—it's wasteful; the flame should be turned down to a low one.

[0058] Energy saving: By directly using medium- and low-temperature thermal energy, the valuable high-temperature thermal energy stored in the inner layer is saved and used for subsequent processes that truly require high temperatures. Actual measurements show that this strategy can save 15-25% of the system's high-grade thermal energy consumption.

[0059] Extended system lifespan: Reducing the number of cycles for the inner high-temperature unit helps extend its service life.

[0060] Beneficial effects This invention discloses a multi-stage thermal storage system based on solid waste-based gradient phase change composite materials and its intelligent dynamic control method. Compared with the prior art, this invention has the following advantages: 1. Compared with existing technologies, the "source-grid-load" coordinated control technology adopted in this invention can minimize the initial investment cost of the heating station and minimize energy waste during operation, thereby improving the system's energy utilization efficiency.

[0061] 2. Energy is stored in the form of pure physical energy, with no pollutant emissions.

[0062] 3. Reduce the consumption of secondary energy and achieve high efficiency and energy saving.

[0063] 4. It uses widely available industrial solid waste as the main raw material, resulting in low overall cost and enabling large-scale application.

[0064] 5. The multi-layer structure enables multi-level energy regulation, allowing for more flexible and agile adjustment of the heat supply, making it more suitable for fluctuating heat sources. Attached Figure Description

[0065] Figure 1 : A schematic diagram of the structure of a multi-stage thermal storage system according to the present invention; Figure 2 : A schematic diagram of a graded structure of a gradient phase change composite material according to the present invention; Figure 3 : A schematic diagram of the industrial application example described in this invention; In the diagram, 1: middle layer thermal storage unit; 2: inner layer thermal storage unit; 3: outer layer thermal storage unit; 4: valve I; 5: valve II; 6: valve III; 7: valve IV; 8: central controller; 9: temperature sensor; 10: inner layer composite material; 11: middle layer composite material; 12: outer layer composite material. Detailed Implementation The present invention will now be described in detail. Before proceeding with the description, it should be understood that the terminology used in this specification and the appended claims should not be construed as limited to its general or dictionary meaning, but rather should be interpreted according to the meaning and concept corresponding to the technical aspects of the invention, based on the principle that the inventors are allowed to appropriately define the terms for the best interpretation. Therefore, the description presented herein is merely a preferred example for illustrative purposes and is not intended to limit the scope of the invention. It should be understood that other equivalents or modifications can be obtained from it without departing from the spirit and scope of the invention.

[0066] The following embodiments are merely examples illustrating implementations of the present invention and do not constitute any limitation on the present invention. Those skilled in the art will understand that modifications made without departing from the spirit and concept of the present invention fall within the protection scope of the present invention. Unless otherwise specified, the reagents and instruments used in the following embodiments are commercially available products.

[0067] Example 1 like Figure 1-2 The multi-stage thermal storage system based on solid waste-based gradient phase change composite materials shown includes the following structure: Middle layer thermal storage unit 1, medium temperature zone (60-150℃), uses short-cut silicon carbide fiber reinforced solid waste ceramic bricks loaded with LiCl microcapsules; Inner heat storage unit 2, high temperature zone (above 150℃), uses fly ash modified magnesia refractory bricks and NaNO3 microcapsules; Outer thermal storage unit 3, low temperature zone (30-60℃), graphene / solid waste-based porous composite material and paraffin; Valve I 4 (outer inlet valve); controls the input of low-temperature hot fluid into the outer heat storage unit 3; Valve II 5 (inner layer steam discharge valve) is used for high-temperature steam discharge and is activated when the inner layer temperature is ≥150℃. Valve Ⅲ 6 (system drain valve), shared across all floors, regulates hot fluid circulation or drains fluid; Valve IV 7 (middle layer inlet regulating valve) controls the input of medium-temperature hot fluid into the middle layer thermal storage unit 1; The central controller 8, based on the thermal coupling mapping model and the adaptive similarity law algorithm, achieves intelligent dynamic control. Temperature sensor 9 monitors the temperature of each thermal storage unit in real time, with a sampling frequency of 1Hz.

[0068] The structural diagrams of the various levels of thermal storage units in the multi-level thermal storage system are shown below. Figure 2 As shown in the figure: The inner composite material 10 comprises fly ash (70 parts), magnesia refractory material (25 parts), and carbon nanotubes (5 parts), loaded with NaNO3 microcapsules. The NaNO3 microcapsules are prepared by spray drying: using a saturated NaNO3 solution as the core material and a gelatin-gum arabic composite solution as the wall material, microcapsules are formed by spray drying, and then loaded onto hierarchical porous solid waste-based framework particles via vacuum impregnation.

[0069] The middle layer composite material 11 includes solid waste ceramic powder (60 parts), short-cut silicon carbide fiber (10 parts), and other additives (30 parts), loaded with LiCl microcapsules.

[0070] The outer composite material 12 includes fly ash (70-85 parts), graphene (5-10 parts), nano-zirconia (3-8 parts), nano-titanium dioxide (2-5 parts), carbon nanotubes (1-3 parts), and storage paraffin.

[0071] The inner microstructure consists of a hierarchical porous framework and a NaNO3 microcapsule complex, forming a spherical granular structure.

[0072] The middle layer microstructure is a composite of fiber-reinforced porous ceramic and LiCl microcapsules.

[0073] The outer microstructure consists of a graphene-modified porous matrix and a paraffin composite.

[0074] in: Inner layer (high-temperature zone): A high thermal conductivity solid waste-based inorganic non-metallic composite material (preferably fly ash modified magnesia refractory brick) is used as the skeleton, and it is manufactured into spherical particles (particle size 10-20mm) and stacked for filling. The energy storage medium is NaNO3 microcapsules, which are loaded into the pores of the skeleton particles through vacuum impregnation, and the phase transition temperature is about 300℃.

[0075] Intermediate layer (intermediate temperature zone): The framework consists of solid waste ceramic bricks loaded with LiCl microcapsules. In a preferred embodiment, the solid waste ceramic bricks are porous solid waste ceramic bricks reinforced with chopped silicon carbide fibers. The preparation method involves using slag and fly ash as the main raw materials (solid waste content >80wt%), incorporating 5-10wt% chopped silicon carbide fibers as reinforcement, and then dry-pressing and sintering at 1150℃. LiCl microcapsules (phase transition temperature ~80℃) are loaded into the porous ceramic bricks via vacuum impregnation.

[0076] Outer layer (low temperature zone): The framework is a graphene / solid waste-based porous material composite, and the energy storage medium is paraffin (phase change temperature ~40℃).

[0077] In a preferred embodiment, the composition ratio of the composite material (by mass fraction) is as follows: fly ash: 70 parts; graphene: 10 parts; nano-zirconia: 3 parts; nano-titanium dioxide: 5 parts; carbon nanotubes: 1 part. This composite material is prepared through a wet mixing, foaming, drying, and sintering process to form a porous framework with high porosity (>70%), into which paraffin wax is filled via vacuum impregnation.

[0078] In a preferred embodiment, the composition ratio of the composite material (by mass fraction) is as follows: fly ash: 85 parts; graphene: 5 parts; nano-zirconia: 8 parts; nano-titanium dioxide: 2 parts; carbon nanotubes: 3 parts. This composite material is prepared through a wet mixing, foaming, drying, and sintering process to form a porous framework with high porosity (>70%), into which paraffin wax is filled via vacuum impregnation.

[0079] In a preferred embodiment, the composition ratio of the composite material (by mass fraction) is as follows: fly ash: 80 parts; graphene: 8 parts; nano-zirconia: 5 parts; nano-titanium dioxide: 3 parts; carbon nanotubes: 2 parts. This composite material is prepared through a wet mixing, foaming, drying, and sintering process to form a porous framework with high porosity (>70%), into which paraffin wax is filled via vacuum impregnation.

[0080] The inner heat transfer backbone structure is an integrated multi-layer heat exchanger, while the middle and outer layers both employ cylindrical vertical bag-type single-layer heat exchangers. Independent valves (part of a valve control system) are installed in each of the inner, middle, and outer layers to regulate flow. Temperature measurement points are also installed in each of the inner, middle, and outer layers, and temperature sensors 9 monitor the temperature of each part in real time and provide feedback to the central controller 8.

[0081] Example 2: Extended Example with Four-Stage Thermal Storage Units This embodiment adds an ultra-high temperature thermal storage unit to the three-level structure of Embodiment 1, forming a four-level thermal storage system to meet the process requirements of higher temperature ranges.

[0082] Structure: From the inside out, it consists of: ultra-high temperature layer (innermost layer), inner layer (high temperature zone), middle layer (medium temperature zone), and outer layer (low temperature zone).

[0083] Ultra-high temperature layer: Skeleton material: Ultra-high thermal conductivity porous ceramic made by adding silicon carbide whiskers to blast furnace slag as the main solid waste raw material and sintering at high temperature.

[0084] Energy storage medium: a eutectic salt mixture of KNO3 and NaCl (phase transition temperature ~400℃), which is directly adsorbed into the porous framework.

[0085] Control method: The ultra-high temperature layer is connected to an independent ultra-high temperature valve and temperature sensor 9. The control strategy of the central controller 8 is upgraded accordingly: when the process requirement temperature is ≥350℃, the ultra-high temperature layer is activated first; when the required temperature is between 150℃ and 350℃, the ultra-high temperature layer is skipped and the inner layer is activated according to the logic of Example 1, and so on.

[0086] Beneficial effects: This four-stage structure increases the total thermal storage capacity of the system by approximately 25%, reaching 1.5 GJ / m³. 3 This system is particularly suitable for applications requiring ultra-high temperature waste heat recovery, such as steel and glass manufacturing. Through intelligent switching and coordinated management of four temperature zones, the overall energy utilization efficiency can be improved by more than 35% compared to traditional systems when facing drastically fluctuating industrial heat sources.

[0087] Example 3: Intelligent Dynamic Control Method A smart dynamic control method based on the multi-stage thermal storage system described in Example 1 is applied to an industrial user requiring a large instantaneous heat flux, demanding that the system provide a continuous 300kW of heat supply to assist in cooling process equipment. The method includes the following steps: (1) System Initialization and Modeling: Based on the user's heat demand, a thermally coupled mapping steady-state model of the overall heat transfer process of the multi-stage thermal storage system is established. An adaptive similarity law is set to allow the system's operating power to change with the heat demand, the core of which is a power-temperature feedback control algorithm. P_set=K_p*(P_demand-P_actual)+K_i*∫(P_demand-P_actual)dt Where P_set is the set power, and K_p and Ki are adaptive gains adjusted according to real-time operating conditions.

[0088] (2) Data acquisition and command generation: Temperature data is collected in real time by temperature sensors 9 at each level (inner layer 130℃, middle layer 75℃, outer layer 35℃, ambient temperature 25℃). The central controller 8 calculates according to the adaptive similarity law and issues adjustment commands to different levels.

[0089] (3) Layered independent response and valve control: Inner layer: Determine if the target temperature (130℃) is ≥150℃? No. Continue to determine if it is ≥60℃? Yes. Then the controller opens valve Ⅲ6 (system drain valve, used for medium and high temperature hot fluid circulation) to drain and release heat.

[0090] Middle layer: Determine if the target temperature (75℃) is ≥80℃? No. Continue to determine if it is ≥40℃? Yes. Then the controller opens its corresponding middle layer inlet valve (function is the same as valve I4, but it is controlled independently), adjusting the opening degree to provide medium-temperature heat.

[0091] Outer layer: Determine if the target temperature (35℃) is ≥30℃? If yes, the controller will open valve I4 (outer layer inlet valve) and valve III6 to initiate outer layer heat release.

[0092] Valve description: Valve I4 (dedicated to outer layer), Valve II5 (inner layer steam discharge valve, not triggered in this example), Valve III6 (system drain main pipe, which can be shared by all layers but is controlled by different logics). The opening and closing of all valves are uniformly executed by the central controller 8.

[0093] (4) Standby and Cycling: If the system has no heat demand, each level enters standby mode. In this case, the system repeats steps (2) to (3) every 10 seconds (time step Δt) to achieve dynamic control.

[0094] Application Results: In this case, the system demonstrated excellent adaptability: Fast response: The response time from receiving the command to stably outputting 300kW of thermal energy is less than 30 seconds.

[0095] Stable power output: During a 10-minute continuous heating process, the output power fluctuation is less than ±10kW.

[0096] High efficiency and energy saving: Through precise "on-demand energy supply" and hierarchical switching, this operation saved users about 25% of high-temperature energy storage, and the overall energy utilization efficiency of the system was calculated to be 88%.

[0097] Example 4: Industrial Application Case An industrial user's process equipment generates a large instantaneous heat flow during production. A heat storage system is required to respond quickly and provide a continuous and stable 300kW heat supply to assist in cooling the equipment. The system is also required to be able to adapt to fluctuations in the upstream heat source.

[0098] Application system configuration: The multi-stage thermal storage system based on solid waste-based gradient phase change composite material described in this invention (as constructed in Example 1) is used. A schematic diagram of its system structure can be found in [reference needed]. Figure 3 As shown in the figure, the system comprises an inner thermal storage unit 2, a middle thermal storage unit 1, and an outer thermal storage unit 3. Each unit's inlet and outlet are connected to a valve control system (including valves I-4, II-5, III-6, and IV-7). Temperature sensors 99 are arranged inside each unit, transmitting all signals to the central controller 88. The controller 88 outputs instructions based on an algorithm to precisely adjust the opening degree of each valve to meet the thermal requirements of the process equipment. This system, through the central controller 8, the valve control system, and the temperature sensor network 9, executes the following intelligent dynamic control method.

[0099] The specific implementation steps of the intelligent dynamic control method are as follows: (1) System Initialization and Model Establishment: Based on the user's heating requirement of 300kW, the target power P_demand = 300kW is set in the central controller 8. An adaptive similarity law is established to ensure that the system's operating power follows the changes in heating demand. The core of this law is the following power feedback control law: P_set(t)=K_p(e(t))·e(t)+K_i(e(t))·∫e(t)dt Where P_set(t) is the total system set power at time t, e(t) = P_demand - P_actual(t) is the real-time power deviation, and K_p and K_i are the proportional and integral gains that are adaptively adjusted according to the magnitude of e(t), used to achieve a balance between fast response and precise control.

[0100] (2) Data Acquisition and Command Generation: After the system starts, the temperature sensors 9 of each layer collect data in real time (inner layer: 130℃, middle layer: 75℃, outer layer: 35℃, ambient temperature: 25℃) and feed it back to the central controller 8. The controller calculates according to the adaptive similarity law, determines that the current actual total power is lower than the target value, and needs to start the middle and outer layers to supply power, and issues adjustment commands containing the target opening value to the corresponding layers.

[0101] (3) Layered independent response and valve control: Each level executes the following judgments and actions in parallel: Inner layer judgment and response: Is the target temperature (130℃) ≥ 150℃? No.

[0102] Continue to determine if the temperature is ≥60℃? Yes. However, based on the "response rate enhancement mechanism" and power allocation results, the current demand can be met by the middle and outer layers, so the inner layer is skipped, its valve remains closed, and it enters a waiting state.

[0103] Mid-level judgment and response: Is the target temperature (75℃) ≥ 80℃? No.

[0104] Continue to determine if it is ≥40℃? Yes.

[0105] Therefore, the central controller 8 executes the instruction: open the inlet regulating valve (valve V) of the middle layer and adjust its opening degree to the calculated 45%, while simultaneously coordinating the adjustment of the opening degree of the system drain valve Ⅲ6 to 60%. The middle layer begins to release medium-temperature heat into the system.

[0106] Outer layer judgment and response: Is the target temperature (35℃) ≥ 30℃? Yes.

[0107] Therefore, the central controller 8 executes the instruction: open the outer inlet valve (valve I4) to 50%, and confirm that the system drain valve III6 is in the coordinated open state. The outer layer begins to release low-temperature heat into the system.

[0108] (4) Standby and Cycling: If the system has no heat demand, each level enters standby mode. In this case, the central controller 8 re-collects data every 10 seconds (time step Δt) and repeats steps (2) to (3) to dynamically fine-tune the opening of each valve in order to achieve accurate power tracking.

[0109] Application performance data: In this industrial case, the system demonstrated outstanding performance: Rapid response: From receiving the control command to the system output power reaching 300kW, the response time is less than 30 seconds, far exceeding that of traditional thermal storage systems (usually more than 5 minutes).

[0110] Power stability: During a 10-minute continuous heating test, the system output power remained stable within the range of 300±10kW, with a fluctuation rate of <3.3%.

[0111] High efficiency and energy saving: By intelligently "skipping" the inner high-temperature zone and directly calling on the energy of the middle and outer layers, about 25% of high-grade thermal energy is saved, making the overall energy utilization efficiency of this operation as high as 88%.

[0112] Adaptation to fluctuations: When the upstream heat source fluctuates, the system successfully controls the tracking error of the output power within 5% through adaptive similarity law and hierarchical adjustment, demonstrating its excellent adaptability to fluctuating heat sources.

[0113] This industrial application case fully demonstrates that the multi-stage thermal storage system and its intelligent dynamic control method described in this invention can effectively meet the stringent requirements of the industrial sector for rapid, stable, efficient, and flexible thermal energy supply.

Claims

1. A multi-stage thermal energy storage system, characterized in that, It includes at least three levels of thermal storage units, each of which uses different heat transfer materials to form a melting point gradient distribution; the thermal storage units are connected in series to form an overall thermal storage system; the thermal storage system also includes an intelligent dynamic control device, which performs precise control of each thermal storage unit in a layered, independent and coordinated manner.

2. The multi-stage thermal storage system according to claim 1, characterized in that, The thermal storage system is a three-level thermal storage unit, which is a thermal storage body composed of three concentric tubes, including an inner thermal storage unit (2), a middle thermal storage unit (1) and an outer thermal storage unit (3) from the inside to the outside.

3. The multi-stage thermal storage system according to claim 2, characterized in that, The heat transfer material of the inner thermal storage unit includes a skeleton material and an energy storage medium material. The skeleton material includes a high thermal conductivity solid waste-based inorganic non-metallic composite material, and the skeleton material adopts a hierarchical porous structure or a granular structure. The energy storage medium material includes NaNO3 microcapsules.

4. The multi-stage thermal storage system according to claim 3, characterized in that, The framework material and the energy storage medium material are combined in the following way: Pretreatment: First, prepare a framework material with a hierarchical porous or granular structure; Load: Under vacuum or pressurized conditions, the energy storage medium material is forcibly impregnated into the pores of the framework material; Shaping: Through capillary force and surface adsorption, the energy storage medium material is firmly locked within the pore network of the framework material, forming a stable composite phase change thermal energy storage body.

5. The multi-stage thermal storage system according to claim 2, characterized in that, The material of the middle-layer thermal storage unit is solid waste ceramic brick loaded with LiCl microcapsules. The preparation method is as follows: using solid waste as the main raw material, during the preparation process, short-cut silicon carbide fibers are added to the ceramic body as reinforcement. Through sintering, a fiber-reinforced porous solid waste ceramic brick is finally produced. Subsequently, LiCl microcapsules are loaded into the pores of the fiber-reinforced porous solid waste ceramic brick through a vacuum impregnation process.

6. The multi-stage thermal storage system according to claim 2, characterized in that, The heat transfer material of the outer thermal storage unit uses graphene / solid waste-based porous composite material as the substrate and paraffin as the energy storage medium. The graphene / solid waste-based porous composite material is a porous material prepared by modifying solid waste material with graphene, nano-zirconia, nano-titanium dioxide and carbon nanotubes. The weight ratio of each component is as follows: solid waste material 70-85 parts, graphene 5-10 parts, nano-zirconia 3-8 parts, nano-titanium dioxide 2-5 parts and carbon nanotubes 1-3 parts.

7. The multi-stage thermal storage system according to claim 6, characterized in that, The method for preparing the outer heat transfer material includes the following steps: Raw material pretreatment: Solid waste materials are ball-milled to a certain particle size, and graphene and carbon nanotubes are ultrasonically dispersed in the presence of a dispersant to form a stable graphene / carbon nanotube suspension. Wet mixing: The treated solid waste material, nano-zirconia, nano-titanium dioxide and graphene / carbon nanotube suspension are thoroughly mixed and stirred to ensure that each component is evenly dispersed to obtain a mixed slurry; Molding and foaming: Add foaming agent and foam stabilizer to the mixed slurry and pour it into the mold; Drying and sintering: First, the material is dried and shaped at 80-120℃, and then sintered at 1000-1200℃ under an inert atmosphere; finally, a graphene / solid waste-based porous composite material with high porosity and a three-dimensional interpenetrating network is obtained. Medium filling: Finally, the paraffin phase change material is filled into the graphene / solid waste-based porous composite material by vacuum impregnation, thereby preparing the outer heat transfer material.

8. The multi-stage thermal storage system according to claim 1, characterized in that, The intelligent dynamic control device includes an execution component, a sensing component, and a control center, enabling independent and coordinated precise control of each thermal storage unit. Its specific structure is as follows: Actuating component: Adjustable heat flux valve system; Each thermal storage unit is connected to an independent set of heat flux valves with precisely adjustable opening at its inlet and / or outlet, i.e., a valve control system. These valves act as actuators, directly controlling the flow rate of the hot fluid entering or leaving each thermal storage unit, thereby regulating the thermal storage / release power of the thermal storage unit. Sensing components: temperature sensor (9) network; A temperature sensor (9) is installed inside each thermal storage unit to monitor the actual temperature of each unit in real time and continuously. Control center: Central controller (8); A unified central controller (8) is set up outside the system; all temperature sensors (9) transmit monitoring data to the central controller (8) in real time through signal lines; the central controller (8) performs calculations according to the built-in intelligent dynamic control algorithm, and then sends control commands to each heat flux valve to adjust its opening degree.

9. A method for intelligent dynamic control of a multi-stage thermal storage system as described in any one of claims 1-8, characterized in that, The method includes: based on user needs and energy requirements under different operating conditions, using an intelligent dynamic control device, adopting a layered independent adjustment method, and utilizing a thermal coupling mapping model, individually setting and adjusting the temperature of each thermal storage unit, thereby achieving intelligent dynamic control of the entire thermal storage system.

10. The intelligent dynamic control method according to claim 9, characterized in that: It also includes a response rate enhancement mechanism, which predicts the heat storage in the inner high-temperature zone based on actual demand. If the demand is large, the energy supply in the inner high-temperature zone is prioritized to be sufficient, and then the supply is gradually extended to the middle and outer layers. If the demand is small, the supply is skipped and goes directly to the middle and outer layers.

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