Cascade heat storage and charging system and method using flue gas waste heat and off-peak electricity

Abstract

The application provides a cascade heat storage and charging system and method using flue gas waste heat and off-peak electricity, which comprises a flue gas-heat conducting medium heat exchanger, a low-temperature heat storage tank, a high-temperature heat storage tank and an electric heater; when flue gas waste heat is available and at a low electricity price, the medium inlet and the medium outlet of the flue gas-heat conducting medium heat exchanger are connected with the bottom outlet of the high-temperature heat storage tank and the inlet of the electric heater respectively, and the outlet of the electric heater is connected with the top inlet of the high-temperature heat storage tank; when flue gas waste heat is available and at a high electricity price, the medium inlet and the medium outlet of the flue gas-heat conducting medium heat exchanger are connected with the bottom outlet of the low-temperature heat storage tank and the top inlet of the low-temperature heat storage tank respectively; when no flue gas waste heat is available and at a low electricity price, the inlet of the electric heater is connected with the bottom outlet of the heat storage tank, and the outlet of the electric heater is connected with the top inlet of the corresponding heat storage tank. The system can complement the advantages of low-grade waste heat and off-peak electricity, and improve the comprehensive energy utilization efficiency.

Description

Technical Field

[0001] This invention belongs to the field of industrial energy conservation and energy storage technology, specifically relating to a cascaded thermal energy storage and co-charging system and method that utilizes waste heat from flue gas and off-peak electricity. Background Technology

[0002] Currently, there are two main technical solutions for recovering and utilizing waste heat from industrial flue gas. The first is direct utilization, such as producing hot water or low-pressure steam through heat exchangers. While this technology is simple, it suffers from fundamental problems such as limited recovery efficiency, low heat grade, and inability to provide stable and continuous heating. It is particularly uneconomical and prone to equipment corrosion when the flue gas temperature is below 150°C. The second is independent electric energy storage heating technology, which utilizes inexpensive electricity during off-peak hours to generate and store heat through methods such as resistance heating, achieving on-demand heat supply. While this technology is flexible, it involves converting high-grade electrical energy entirely into medium- to low-grade heat energy, resulting in significant energy losses, poor thermodynamic efficiency, and still relatively high operating costs. Furthermore, the initial investment for large-capacity heat storage devices is substantial. Neither existing single technical approach can simultaneously achieve economic efficiency, high efficiency, and flexibility.

[0003] To address the aforementioned issues, it is necessary to propose a rationally designed and effective cascaded thermal storage and co-charging system and method that utilizes waste heat from flue gas and off-peak electricity to solve these problems. Summary of the Invention

[0004] The present invention aims to at least solve one of the technical problems existing in the prior art, and to provide a cascaded thermal storage and co-charging system and method that utilizes waste heat from flue gas and off-peak electricity.

[0005] This invention provides a cascaded thermal energy storage and co-charging system utilizing waste heat from flue gas and off-peak electricity, comprising a flue gas-thermal medium heat exchanger, a low-temperature thermal storage tank, a high-temperature thermal storage tank, and an electric heater; the flue gas inlet of the flue gas-thermal medium heat exchanger is connected to industrial flue gas; wherein... When the waste heat of the flue gas is available and the electricity price is at a low point, the medium inlet of the flue gas-thermal medium heat exchanger is connected to the bottom outlet of the high-temperature heat storage tank, the medium outlet of the flue gas-thermal medium heat exchanger is connected to the inlet of the electric heater, and the outlet of the electric heater is connected to the top inlet of the high-temperature heat storage tank. When the waste heat from the flue gas is available and the electricity price is at its lowest point, the medium inlet of the flue gas-thermal medium heat exchanger is connected to the bottom outlet of the low-temperature heat storage tank, and the medium outlet of the flue gas-thermal medium heat exchanger is connected to the top inlet of the low-temperature heat storage tank. When there is no waste heat from flue gas available and electricity prices are low, the inlet of the electric heater is connected to the bottom outlet of the high-temperature heat storage tank or the low-temperature heat storage tank, and the outlet of the electric heater is connected to the top inlet of the corresponding heat storage tank.

[0006] Optionally, the system may also include a user-side heat exchanger; When a user needs heat energy, the inlet of the user-side heat exchanger is connected to the top outlet of the high-temperature heat storage tank or the low-temperature heat storage tank, and the outlet of the user-side heat exchanger is connected to the bottom inlet of the corresponding heat storage tank.

[0007] Optionally, the system further includes a first control valve; The inlet of the first control valve is connected to the medium outlet of the flue gas-heat transfer medium heat exchanger, and the outlet of the first control valve is connected to the top inlet of the low-temperature heat storage tank.

[0008] Optionally, the system further includes a second control valve; The inlet of the second control valve is selectively connected to the bottom outlet of the high-temperature heat storage tank and the bottom outlet of the low-temperature heat storage tank, and the outlet of the second control valve is connected to the medium inlet of the flue gas-heat transfer medium heat exchanger.

[0009] Optionally, the system may also include a heat transfer medium circulation pump; The heat transfer medium circulation pump is connected to the second control valve and the flue gas-heat transfer medium heat exchanger, respectively.

[0010] Optionally, the system may also include a third control valve; The inlet of the third control valve is connected to the top outlet of the high-temperature thermal storage tank or the low-temperature thermal storage tank, and the outlet of the third control valve is connected to the bottom inlet of the corresponding thermal storage tank.

[0011] Optionally, the system may also include a controller; The controller is used to automatically control the connection between the flue gas-heat transfer medium heat exchanger, the low-temperature heat storage tank, the high-temperature heat storage tank, and the electric heater based on the waste heat of the flue gas and the electricity price.

[0012] Another aspect of the present invention provides a cascaded thermal energy storage and co-charging method utilizing flue gas waste heat and off-peak electricity, employing the cascaded thermal energy storage and co-charging system utilizing flue gas waste heat and off-peak electricity described above; wherein, the method includes: When the waste heat of flue gas is available and the electricity price is low, the heat transfer medium in the high-temperature heat storage tank flows into the flue gas-heat transfer medium heat exchanger for preheating through waste heat exchange of flue gas, then flows into the electric heater for heating and temperature rise, and finally is transported to the high-temperature heat storage tank for heat storage. When the waste heat of flue gas is available and the electricity price is at its lowest, the heat transfer medium in the low-temperature heat storage tank flows into the flue gas-heat transfer medium heat exchanger, is heated by the waste heat of flue gas, and is then transported to the low-temperature heat storage tank for heat storage. When there is no waste heat from flue gas available and electricity prices are low, the heat transfer medium in the high-temperature heat storage tank or the low-temperature heat storage tank flows into the electric heater for heating, and then is transported to the corresponding heat storage tank for heat storage.

[0013] Optionally, the method further includes: When a user needs heat energy, the heat transfer medium in the high-temperature heat storage tank or the low-temperature heat storage tank flows into the user-side heat exchanger for heat exchange, and the heat transfer medium after heat exchange is then transported to the corresponding heat storage tank.

[0014] Optionally, the method further includes: The controller automatically controls the cascaded thermal energy storage and coordinated charging based on flue gas waste heat and electricity price.

[0015] This invention relates to a cascaded thermal energy storage and co-charging system and method utilizing waste heat from flue gas and off-peak electricity. The system incorporates a flue gas-heat transfer medium heat exchanger and an electric heater, employing a tiered utilization approach of "waste heat preheating + electric energy heating." This prioritizes the use of low-grade waste heat, significantly reducing energy losses during direct heating with high-grade electricity. Compared to a pure electric thermal energy storage system with the same heat storage capacity, this co-charging mode can save 30% to 50% of electricity consumption. The system maximizes the utilization of zero-cost waste heat from flue gas and ensures that the electric heater operates only during off-peak hours when electricity prices are lowest. The optimized combination of low-cost energy sources makes the energy cost per unit of heating far lower than that of pure electric heating or traditional boiler solutions, resulting in significant economic benefits. Cascaded thermal storage tanks achieve effective energy storage and time shifting, completely decoupling the intermittent fluctuations of heat sources from the continuous demand of users, providing users with stable and uninterrupted high-quality heat energy. It transforms the rigid heating demand of enterprises into a flexible and dispatchable load that is concentrated in the off-peak hours, with peak shaving and valley filling capabilities, which helps to absorb fluctuating renewable energy sources and can create additional value by participating in the electricity ancillary services market. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a cascaded thermal storage and co-charging system utilizing waste heat from flue gas and off-peak electricity, according to an embodiment of the present invention. Figure 2 This is a schematic flowchart of another embodiment of the present invention, which illustrates a cascaded thermal storage and synergistic energy charging method utilizing waste heat from flue gas and off-peak electricity. Detailed Implementation

[0017] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0018] like Figure 1As shown, one aspect of the present invention provides a cascaded thermal energy storage and co-charging system utilizing waste heat from flue gas and off-peak electricity, comprising a flue gas-thermal medium heat exchanger 1, a low-temperature thermal storage tank 2, an electric heater 3, a high-temperature thermal storage tank 4, a thermal medium circulation pump 5, a user-side heat exchanger 6, a first control valve 7, a second control valve 8, a third control valve 9, and a controller 10. The flue gas inlet of the flue gas-thermal medium heat exchanger 1 is connected to industrial flue gas.

[0019] When the waste heat of the flue gas is available and the electricity price is low, the medium inlet of the flue gas-thermal medium heat exchanger 1 is connected to the bottom outlet of the high-temperature heat storage tank 4, the medium outlet of the flue gas-thermal medium heat exchanger 1 is connected to the inlet of the electric heater 3, and the outlet of the electric heater 3 is connected to the top inlet of the high-temperature heat storage tank 4.

[0020] Specifically, a coordinated charging mode is implemented when waste heat from the flue gas is available and electricity prices are low. The low-temperature heat transfer medium at the bottom of the high-temperature heat storage tank 4 flows into the flue gas-heat transfer medium heat exchanger 1. The waste heat from the flue gas preheats the low-temperature heat transfer medium by exchanging heat in the flue gas-heat transfer medium heat exchanger 1. Then, the low-temperature heat transfer medium flows into the electric heater 3 for heating to the target temperature, and finally it is transported to the top of the high-temperature heat storage tank 4 for heat storage.

[0021] When the waste heat from the flue gas is available and the electricity price is at its lowest point, the medium inlet of the flue gas-thermal medium heat exchanger 1 is connected to the bottom outlet of the low-temperature heat storage tank 2, and the medium outlet of the flue gas-thermal medium heat exchanger 1 is connected to the top inlet of the low-temperature heat storage tank 2.

[0022] Specifically, when waste heat from the flue gas is available and electricity prices are at their lowest, a separate waste heat charging mode is implemented. The low-temperature heat transfer medium at the bottom of the low-temperature heat storage tank 2 enters the flue gas-heat transfer medium heat exchanger 1. The waste heat from the flue gas is exchanged in the flue gas-heat transfer medium heat exchanger 1 to heat the low-temperature heat transfer medium to the target temperature, and then it is transported to the top of the low-temperature heat storage tank 2 for heat storage, thus reserving preheating medium for the subsequent collaborative charging mode.

[0023] When there is no waste heat from flue gas available and electricity prices are low, the inlet of the electric heater 3 is connected to the bottom outlet of the high-temperature heat storage tank 4 or the low-temperature heat storage tank 2, and the outlet of the electric heater 3 is connected to the top inlet of the corresponding heat storage tank.

[0024] Specifically, when there is no waste heat from flue gas available and electricity prices are low, a separate electric energy charging mode is implemented. The low-temperature heat transfer medium at the bottom of the high-temperature heat storage tank 4 flows into the electric heater 3 and is heated to the target temperature, and then transported to the top of the high-temperature heat storage tank 4 for heat storage. Alternatively, the low-temperature heat transfer medium at the bottom of the low-temperature heat storage tank 2 flows into the electric heater 3 and is heated to the target temperature, and then transported to the top of the low-temperature heat storage tank 2 for heat storage.

[0025] It should be noted that the heat transfer medium can be selected from heat transfer oil or molten salt depending on the operating temperature; this embodiment does not make any specific limitations.

[0026] This invention provides a cascaded thermal storage and co-charging energy system utilizing flue gas waste heat and off-peak electricity. This system automatically switches the charging path based on flue gas waste heat and electricity price signals (off-peak / high-peak). By co-utilizing flue gas waste heat and off-peak electricity, it achieves tiered heating (waste heat preheating + electric heating) when waste heat is available and electricity prices are low; utilizes only waste heat for storage when waste heat is available but electricity prices are high; and uses only electric heating for storage when there is no waste heat but electricity prices are low. This optimizes energy costs and minimizes energy loss under various operating conditions.

[0027] This invention relates to a cascaded thermal energy storage and co-charging system utilizing waste heat from flue gas and off-peak electricity. By incorporating a flue gas-heat transfer medium heat exchanger and an electric heater, it employs a tiered utilization method of "waste heat preheating + electric energy heating," prioritizing the use of low-grade waste heat and significantly reducing energy losses during direct heating with high-grade electricity. Compared to a pure electric thermal energy storage system with the same heat storage capacity, this co-charging mode can save 30% to 50% of electricity consumption. The system maximizes the utilization of zero-cost waste heat from flue gas and ensures that the electric heater operates only during off-peak hours when electricity prices are lowest, achieving two low-cost... The optimized combination of energy sources results in a unit heating energy cost that is far lower than that of pure electric heating or traditional boiler solutions, leading to significant economic benefits. The cascaded thermal storage tanks achieve effective energy storage and time shifting, completely decoupling the intermittent fluctuations of the heat source from the continuous demand of the user side, providing users with stable and uninterrupted high-quality heat energy. It transforms the rigid heating demand of enterprises into a flexible and dispatchable load that is concentrated in the off-peak hours, with peak shaving and valley filling capabilities, which helps to absorb fluctuating renewable energy sources and can create additional value by participating in the electricity ancillary services market.

[0028] For example, such as Figure 1 As shown, the system also includes a user-side heat exchanger 6. When a user needs heat energy, the inlet of the user-side heat exchanger 6 is connected to the top outlet of the high-temperature heat storage tank 4 or the low-temperature heat storage tank 2, and the outlet of the user-side heat exchanger 6 is connected to the bottom inlet of the corresponding heat storage tank.

[0029] Specifically, when a user needs heat energy, a heating mode is activated. The high-temperature heat transfer medium at the top of the high-temperature heat storage tank 4 flows into the user-side heat exchanger 6 to release heat, and then is transported to the bottom of the high-temperature heat storage tank 4. Alternatively, the high-temperature heat transfer medium at the top of the low-temperature heat storage tank 2 flows into the user-side heat exchanger 6 to release heat, and then is transported to the bottom of the low-temperature heat storage tank 2.

[0030] In this embodiment, the thermal storage system and the heat-consuming end are decoupled by setting up a heat exchanger on the user side. Users can flexibly access the thermal energy in the high-temperature or low-temperature thermal storage tank according to the required temperature, ensuring the stability and continuity of heating supply, while improving the system's applicability and responsiveness.

[0031] For example, such as Figure 1 As shown, the system also includes a first control valve 7; the inlet of the first control valve 7 is connected to the medium outlet of the flue gas-heat transfer medium heat exchanger 1, and the outlet of the first control valve 7 is connected to the top inlet of the low-temperature heat storage tank 2. In other words, the first control valve 7 is located in the connecting pipe between the medium outlet of the flue gas-heat transfer medium heat exchanger 1 and the top inlet of the low-temperature heat storage tank 2.

[0032] In this embodiment, by setting a first control valve, the preheated medium can be directly introduced into the cryogenic heat storage tank when only waste heat is used for charging.

[0033] For example, such as Figure 1 As shown, the system also includes a second control valve 8; the inlet of the second control valve 8 is selectively connected to the bottom outlet of the high-temperature heat storage tank 4 and the bottom outlet of the low-temperature heat storage tank 2, and the outlet of the second control valve 8 is connected to the medium inlet of the flue gas-heat transfer medium heat exchanger 1. That is to say, the second control valve 8 is a three-way valve.

[0034] In this embodiment, the outlets of the high-temperature and low-temperature thermal storage tanks are flexibly switched through the second control valve, allowing the system to select whether to heat the medium in the high-temperature or low-temperature thermal storage tank based on the waste heat of the flue gas and the electricity price, thereby improving the system's adaptability and operational flexibility to different operating conditions.

[0035] For example, such as Figure 1 As shown, the system also includes a heat transfer medium circulation pump 5; the heat transfer medium circulation pump 5 is connected to the second control valve 8 and the flue gas-heat transfer medium heat exchanger 1 respectively.

[0036] In this embodiment, a heat transfer medium circulation pump is installed to provide power for the circulation of the medium between the heat exchanger, electric heater, and heat storage tank, ensuring that the system can operate stably and controllably in various modes. This is a key component for realizing active thermal management.

[0037] For example, such as Figure 1 As shown, the system also includes a third control valve 9; the inlet of the third control valve 9 is connected to the top outlet of the high-temperature thermal storage tank 4 or the low-temperature thermal storage tank 2, and the outlet of the third control valve 9 is connected to the bottom inlet of the corresponding thermal storage tank.

[0038] In this embodiment, the flow direction and on / off state of the medium in the heating circuit are controlled by the third control valve, thereby realizing the start and stop of the heating mode and the selection of the temperature source, which further improves the control accuracy and reliability of the system during the heat release stage.

[0039] For example, such as Figure 1 As shown, the system also includes a controller 10; the controller 10 is used to automatically control the connection between the flue gas-heat transfer medium heat exchanger 1, the low-temperature heat storage tank 2, the electric heater 3 and the high-temperature heat storage tank 4 according to the flue gas waste heat and electricity price.

[0040] Specifically, the controller 10 receives input signals such as flue gas temperature, tank liquid level and temperature, user load and real-time electricity price, and sends control commands to the heat transfer medium circulation pump 5, electric heater 3 and each control valve according to the preset optimization control algorithm, so as to realize the automatic switching of each operating mode and optimal economic operation.

[0041] In this embodiment, the system achieves fully automatic intelligent operation through a controller. Based on parameters such as real-time flue gas status, electricity price signal, tank temperature and user load, the system automatically switches operating modes and controls various valves and actuators, significantly improving the system's economy, efficiency and reliability, and reducing the need for manual intervention.

[0042] like Figure 1 As shown, the working process of the cascaded thermal storage and co-charging energy system utilizing waste heat from flue gas and off-peak electricity of the present invention can be as follows: 1) Collaborative charging mode: Triggered when waste heat from flue gas is available and electricity prices are low. The heat transfer medium circulation pump 5 starts, the second control valve 8 connects to the high-temperature heat storage tank 4, and the first control valve 7 closes. The low-temperature heat transfer medium is drawn out from the bottom outlet of the high-temperature heat storage tank 4, preheated by the flue gas-heat transfer medium heat exchanger 1, then heated to the target high temperature by the electric heater 3, and finally injected into the top inlet of the high-temperature heat storage tank 4 for storage.

[0043] 2) Independent waste heat charging mode: Triggered when waste heat from flue gas is available but electricity prices are high. The heat transfer medium circulation pump 5 starts, the second control valve 8 connects to the low-temperature heat storage tank 2, and the first control valve 7 opens. The low-temperature heat transfer medium is drawn out from the bottom outlet of the low-temperature heat storage tank 2, heated by the flue gas-heat transfer medium heat exchanger 1, and then returned to the top inlet of the low-temperature heat storage tank 2 for storage.

[0044] 3) Standalone power charging mode: Triggered when electricity prices are low but there is no residual heat. The heat transfer medium circulation pump 5 and the second control valve 8 are connected to the target heat storage tank (low temperature heat storage tank 2 or high temperature heat storage tank 4). The low temperature heat transfer medium is drawn out from the bottom outlet of the target heat storage tank, heated directly to the target temperature by the electric heater 3, and then returned to the top inlet of the target heat storage tank.

[0045] 4) Heating Mode: Triggered when users have heat demand. The charging circuit stops, the third control valve 9 opens, and high-temperature heat transfer medium is drawn from the top outlet of the high-temperature heat storage tank 4 or the low-temperature heat storage tank 2 according to the required temperature. After flowing through the user-side heat exchanger 6 to release heat and supply heat, it returns to the bottom inlet of the corresponding heat storage tank.

[0046] like Figure 2 As shown, another aspect of the present invention provides a cascaded thermal energy storage and co-charging method S100 that utilizes waste heat from flue gas and off-peak electricity, employing the cascaded thermal energy storage and co-charging system for utilizing waste heat from flue gas and off-peak electricity described above; the specific structural features of this cascaded thermal energy storage and co-charging system for utilizing waste heat from flue gas and off-peak electricity have been described in detail above and will not be repeated here.

[0047] Specifically, the cascaded thermal storage and synergistic energy charging method S100 of the present invention, which utilizes waste heat from flue gas and off-peak electricity, may include: S110. When the waste heat of the flue gas is available and the electricity price is low, the heat transfer medium in the high-temperature heat storage tank flows into the flue gas-heat transfer medium heat exchanger for preheating through waste heat exchange of the flue gas, then flows into the electric heater for heating and temperature rise, and finally is transported to the high-temperature heat storage tank for heat storage.

[0048] Specifically, such as Figure 1 As shown, a coordinated charging mode is implemented when waste heat from the flue gas is available and electricity prices are low. The low-temperature heat transfer medium at the bottom of the high-temperature heat storage tank 4 flows into the flue gas-heat transfer medium heat exchanger 1. The waste heat from the flue gas preheats the low-temperature heat transfer medium by exchanging heat in the flue gas-heat transfer medium heat exchanger 1. Then, the low-temperature heat transfer medium flows into the electric heater 3 for heating to the target temperature, and finally it is transported to the top of the high-temperature heat storage tank 4 for heat storage.

[0049] S120. When the waste heat of the flue gas is available and the electricity price is at its lowest, the heat transfer medium in the low-temperature heat storage tank flows into the flue gas-heat transfer medium heat exchanger, is heated by the waste heat of the flue gas, and is then transported to the low-temperature heat storage tank for heat storage.

[0050] Specifically, such as Figure 1 As shown, when the waste heat from the flue gas is available and the electricity price is at its lowest point, a separate waste heat charging mode is implemented. The low-temperature heat transfer medium at the bottom of the low-temperature heat storage tank 2 enters the flue gas-heat transfer medium heat exchanger 1. The waste heat from the flue gas is exchanged in the flue gas-heat transfer medium heat exchanger 1 to heat the low-temperature heat transfer medium to the target temperature, and then it is transported to the top of the low-temperature heat storage tank 2 for heat storage, reserving preheating medium for the subsequent collaborative charging mode.

[0051] S130. When there is no waste heat from flue gas available and the electricity price is low, the heat transfer medium in the high-temperature heat storage tank or the low-temperature heat storage tank flows into the electric heater for heating, and then is transported to the corresponding heat storage tank for heat storage.

[0052] Specifically, such as Figure 1 As shown, when there is no waste heat from flue gas available and electricity prices are low, a separate electric energy charging mode is implemented. The low-temperature heat transfer medium at the bottom of the high-temperature heat storage tank 4 flows into the electric heater 3 and is heated to the target temperature, then transported to the top of the high-temperature heat storage tank 4 for heat storage. Alternatively, the low-temperature heat transfer medium at the bottom of the low-temperature heat storage tank 2 flows into the electric heater 3 and is heated to the target temperature, then transported to the top of the low-temperature heat storage tank 2 for heat storage.

[0053] For example, the method further includes: When a user needs heat energy, the heat transfer medium in the high-temperature heat storage tank or the low-temperature heat storage tank flows into the user-side heat exchanger for heat exchange, and the heat transfer medium after heat exchange is then transported to the corresponding heat storage tank.

[0054] Specifically, when a user needs heat energy, a heating mode is activated. The high-temperature heat transfer medium at the top of the high-temperature heat storage tank 4 flows into the user-side heat exchanger 6 to release heat, and then is transported to the bottom of the high-temperature heat storage tank 4. Alternatively, the high-temperature heat transfer medium at the top of the low-temperature heat storage tank 2 flows into the user-side heat exchanger 6 to release heat, and then is transported to the bottom of the low-temperature heat storage tank 2.

[0055] For example, the method further includes: The controller automatically controls the cascaded thermal energy storage and coordinated charging based on flue gas waste heat and electricity price.

[0056] Specifically, the controller 10 receives input signals such as flue gas temperature, tank liquid level and temperature, user load and real-time electricity price, and sends control commands to the heat transfer medium circulation pump 5, electric heater 3 and each control valve according to the preset optimization control algorithm, so as to realize the automatic switching of each operating mode and the optimal economic operation, and automatically control the cascaded thermal storage and coordinated energy charging.

[0057] The cascaded thermal storage and synergistic energy charging method for utilizing waste heat from flue gas and off-peak electricity of the present invention has the following beneficial effects: 1) Improved comprehensive energy utilization efficiency: By using a tiered utilization method of "waste heat preheating + electric energy heating", low-grade waste heat is prioritized for use, significantly reducing energy loss during the direct heating process of high-grade electric energy. Compared with a pure electric thermal storage system with the same heat storage capacity, the synergistic charging mode of this invention can save 30% to 50% of electricity consumption.

[0058] 2) Reduced system operating costs: The system maximizes the use of zero-cost flue gas waste heat and ensures that the electric heaters operate only during off-peak hours when electricity prices are lowest. This optimized combination of two low-cost energy sources results in a unit heating energy cost that is far lower than that of pure electric heating or traditional boiler solutions, leading to significant economic benefits.

[0059] 3) Enhanced heating reliability: The design of cascaded thermal storage tanks enables effective energy storage and time shifting, completely decoupling the intermittent fluctuations of the heat source from the continuous needs of the user side, providing users with stable and uninterrupted high-quality thermal energy.

[0060] 4) Grid-friendly: This invention transforms the rigid heating demand of enterprises into a flexible and dispatchable load that uses electricity in a concentrated manner during off-peak hours. It has the ability to shave peaks and fill valleys, which helps to absorb fluctuating renewable energy sources and can create additional value by participating in the electricity ancillary services market.

[0061] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A cascaded thermal storage and co-charging system utilizing waste heat from flue gas and off-peak electricity, characterized in that, It includes a flue gas-heat transfer medium heat exchanger, a low-temperature heat storage tank, a high-temperature heat storage tank, and an electric heater; the flue gas inlet of the flue gas-heat transfer medium heat exchanger is used to connect with industrial flue gas; wherein, When the waste heat of the flue gas is available and the electricity price is at a low point, the medium inlet of the flue gas-thermal medium heat exchanger is connected to the bottom outlet of the high-temperature heat storage tank, the medium outlet of the flue gas-thermal medium heat exchanger is connected to the inlet of the electric heater, and the outlet of the electric heater is connected to the top inlet of the high-temperature heat storage tank. When the waste heat from the flue gas is available and the electricity price is at its lowest point, the medium inlet of the flue gas-thermal medium heat exchanger is connected to the bottom outlet of the low-temperature heat storage tank, and the medium outlet of the flue gas-thermal medium heat exchanger is connected to the top inlet of the low-temperature heat storage tank. When there is no waste heat from flue gas available and electricity prices are low, the inlet of the electric heater is connected to the bottom outlet of the high-temperature heat storage tank or the low-temperature heat storage tank, and the outlet of the electric heater is connected to the top inlet of the corresponding heat storage tank.

2. The system according to claim 1, characterized in that, The system also includes a user-side heat exchanger; When a user needs heat energy, the inlet of the user-side heat exchanger is connected to the top outlet of the high-temperature heat storage tank or the low-temperature heat storage tank, and the outlet of the user-side heat exchanger is connected to the bottom inlet of the corresponding heat storage tank.

3. The system according to claim 1, characterized in that, The system also includes a first control valve; The inlet of the first control valve is connected to the medium outlet of the flue gas-heat transfer medium heat exchanger, and the outlet of the first control valve is connected to the top inlet of the low-temperature heat storage tank.

4. The system according to claim 1, characterized in that, The system also includes a second control valve; The inlet of the second control valve is selectively connected to the bottom outlet of the high-temperature heat storage tank and the bottom outlet of the low-temperature heat storage tank, and the outlet of the second control valve is connected to the medium inlet of the flue gas-heat transfer medium heat exchanger.

5. The system according to claim 4, characterized in that, The system also includes a heat transfer medium circulation pump; The heat transfer medium circulation pump is connected to the second control valve and the flue gas-heat transfer medium heat exchanger, respectively.

6. The system according to claim 2, characterized in that, The system also includes a third control valve; The inlet of the third control valve is connected to the top outlet of the high-temperature thermal storage tank or the low-temperature thermal storage tank, and the outlet of the third control valve is connected to the bottom inlet of the corresponding thermal storage tank.

7. The system according to claim 1, characterized in that, The system also includes a controller; The controller is used to automatically control the connection between the flue gas-heat transfer medium heat exchanger, the low-temperature heat storage tank, the high-temperature heat storage tank, and the electric heater based on the waste heat of the flue gas and the electricity price.

8. A method for cascaded thermal storage and coordinated energy charging utilizing waste heat from flue gas and off-peak electricity, characterized in that, The method employs the cascaded thermal energy storage and co-charging system utilizing waste heat from flue gas and off-peak electricity as described in any one of claims 1 to 7; wherein the method includes: When the waste heat of flue gas is available and the electricity price is low, the heat transfer medium in the high-temperature heat storage tank flows into the flue gas-heat transfer medium heat exchanger for preheating through waste heat exchange of flue gas, then flows into the electric heater for heating and temperature rise, and finally is transported to the high-temperature heat storage tank for heat storage. When the waste heat of flue gas is available and the electricity price is at its lowest, the heat transfer medium in the low-temperature heat storage tank flows into the flue gas-heat transfer medium heat exchanger, is heated by the waste heat of flue gas, and is then transported to the low-temperature heat storage tank for heat storage. When there is no waste heat from flue gas available and electricity prices are low, the heat transfer medium in the high-temperature heat storage tank or the low-temperature heat storage tank flows into the electric heater for heating, and then is transported to the corresponding heat storage tank for heat storage.

9. The method according to claim 8, characterized in that, The method further includes: When a user needs heat energy, the heat transfer medium in the high-temperature heat storage tank or the low-temperature heat storage tank flows into the user-side heat exchanger for heat exchange, and the heat transfer medium after heat exchange is then transported to the corresponding heat storage tank.

10. The method according to claim 8, characterized in that, The method further includes: The controller automatically controls the cascaded thermal energy storage and coordinated charging based on flue gas waste heat and electricity price.

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