Heat storage and release device and method suitable for cascade heat source and valley electricity utilization

Abstract

The invention discloses a heat storage and release device suitable for cascade heat source and valley electricity utilization, the heat storage and release device comprises a phase change heat storage module and a shell-and-tube heat exchanger, the phase change heat storage module comprises a heating box, a plurality of graphite crucibles are placed in the heating box, phase change materials are placed in the graphite crucibles, an alundum tube is arranged in the heating box, and the alundum tube extends out of the top of the heating box; the end of the air outlet pipe is further connected with a connecting pipe, and the connecting pipe is connected with a shell pass inlet of the shell-and-tube heat exchanger. A shell pass outlet of the shell-and-tube heat exchanger is connected with the interior of the heating box through an exhaust pipe, and a variable-frequency air blower is arranged on the exhaust pipe. The invention further discloses a heat storage and release method suitable for cascade heat source and valley electricity utilization. According to the device, low-grade heat sources such as industrial waste heat and solar energy can be fully utilized, and space-time transfer of energy is achieved in combination with electric power in the valley electricity period; and by optimizing the structure of the phase change heat storage module, the heat storage and release efficiency and the operation stability are remarkably improved.

Description

Technical Field

[0001] This invention belongs to the technical field of energy storage and efficient utilization equipment, specifically relating to a heat storage and release device suitable for cascade heat sources and off-peak electricity utilization, and also to a heat storage and release method suitable for cascade heat sources and off-peak electricity utilization. Background Technology

[0002] Renewable energy sources generally suffer from intermittency and volatility. For example, solar energy is affected by day and night cycles and weather conditions, while wind energy is constrained by wind speed variations, leading to unstable energy supply. Meanwhile, although cascade heat sources such as industrial waste heat, geothermal energy, and solar thermal collectors have high energy utilization potential, their large temperature differences and uneven spatial and temporal distribution make direct and efficient utilization difficult. Therefore, how to achieve stable storage and efficient utilization of intermittent energy sources and waste heat has become a critical issue that urgently needs to be addressed in the energy sector.

[0003] Phase change thermal energy storage (PCE) technology, with its advantages of high energy density, stable storage and release temperatures, and low energy loss, has become one of the core supporting technologies in the field of solar thermal utilization. Numerous studies have shown that PCE systems can significantly improve the absorption capacity of renewable energy while maintaining energy conversion efficiency. However, for storage and release systems that utilize cascaded heat sources (such as industrial waste heat, low-temperature solar energy, and geothermal energy) in conjunction with off-peak electricity from the power grid, a mature integrated optimization method has not yet been formed. On the one hand, different heat sources have significant differences in temperature quality and supply time periods; how to achieve cascaded utilization and spatiotemporal matching of heat sources through system design to avoid energy waste remains a critical technical challenge. On the other hand, the development of experimental devices for verifying multi-heat source coupling and control strategies is severely lagging, directly hindering the progress of cascaded thermal energy storage systems from the laboratory to engineering applications. Summary of the Invention The purpose of this invention is to provide a heat storage and release device suitable for cascade heat sources and off-peak electricity utilization, which solves the problems of low coupling efficiency of multiple heat sources and unstable heat storage and release in the prior art.

[0004] Another object of the present invention is to provide a heat storage and release method suitable for cascaded heat sources and off-peak electricity utilization.

[0005] The technical solution adopted in this invention is a heat storage and release device suitable for cascade heat sources and off-peak electricity utilization, including a phase change heat storage module and a shell-and-tube heat exchanger. The phase change heat storage module includes a heating box, inside which are placed multiple graphite crucibles containing phase change materials. A corundum tube is installed inside the heating box, extending from the top of the heating box and connected to an exhaust pipe at its extended end. The end of the exhaust pipe is also connected to a connecting pipe, which is connected to the inlet of the shell-and-tube heat exchanger. The outlet of the shell-and-tube heat exchanger is connected to the interior of the heating box through an exhaust pipe, on which a variable frequency blower is installed.

[0006] The invention is further characterized in that, A second valve is installed on the exhaust pipe; the exhaust pipe is also connected to the second heat source intake pipe; a first valve is installed on the second heat source intake pipe.

[0007] A fourth valve is installed on the connecting pipe, which is also connected to the first heat source inlet pipe; a third valve is installed on the first heat source inlet pipe.

[0008] The heating chamber is also equipped with multiple K-type armored thermocouples. One end of the K-type armored thermocouple is in contact with the phase change material, and the other end extends out of the top of the heating chamber.

[0009] The phase change material is an Al-Cu-Si alloy.

[0010] The vent pipe and the corundum pipe are connected by a 304 stainless steel pagoda head.

[0011] Another technical solution adopted in this invention is a heat storage and release method applicable to cascaded heat sources and off-peak electricity utilization, which is implemented according to the following steps: Step 1: Heat storage for the phase change thermal storage module: The heating process of the phase change thermal storage module is achieved through a shell-and-tube heat exchanger, a heat source, and off-peak electricity supply; specifically: When the heat source is hot water with a temperature higher than 80℃, the hot water is introduced into the shell-and-tube heat exchanger, and the fourth valve and the second valve are opened. At this time, the variable frequency blower is turned on, and air enters the shell-and-tube heat exchanger to exchange heat with the hot water in the tubes. When the temperature difference between the air and the hot water in the shell-and-tube heat exchanger is less than 12℃, the fourth valve and the second valve are closed, and the phase change heat storage module completes the initial heating and the temperature rises to T2. Using a high-temperature air heat source with a gas temperature above 80°C, based on the previous step, simultaneously open the third valve and the first valve, close the fourth valve and the second valve, switch to the air-based heating mode, and heat the phase change material. When the temperature difference between the air and the phase change material in the phase change heat storage module is less than 12°C, the phase change heat storage module completes heating, the temperature rises to T3, and the third valve and the first valve are closed. Once the power system enters off-peak electricity price periods, the heating box is activated to heat the phase change material to the target temperature T4, thus completing the heat storage process. Step 2: Heat release from the phase change thermal storage module: During the heat release process, open the fourth valve and the second valve, and introduce flowing air into the phase change thermal storage module through a variable frequency blower. At the same time, inject room temperature water into the tube side of the shell-and-tube heat exchanger. The air and room temperature water exchange heat in the shell-and-tube heat exchanger. The air flow rate is changed by adjusting the variable frequency blower, and the flow rate of the room temperature water is adjusted simultaneously. The final outlet water temperature is obtained by using a fitting formula, which is shown in equation (1): (1) In the formula, x is the flow rate of water at room temperature, in kg / h; y is the air flow rate of the variable frequency blower, in kg / h; and z is the outlet water temperature, in °C.

[0012] The beneficial effects of this invention are as follows: The heat storage and release device applicable to cascaded heat sources and off-peak electricity utilization achieves efficient coupling and utilization of multiple heat sources through modular design. On the one hand, it can fully utilize low-grade heat sources such as industrial waste heat and solar energy, combined with off-peak electricity, to realize the spatiotemporal transfer of energy; on the other hand, by optimizing the structure and control method of the phase change heat storage module, the heat storage and release efficiency and operational stability are significantly improved, providing a stable and economical clean energy solution for building heating systems. Simultaneously, this heat storage and release device can be flexibly expanded according to different application scenarios, providing reliable technical support for building new integrated energy systems. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the heat storage and release device of the present invention, applicable to cascade heat sources and off-peak electricity utilization; Figure 2 This is a schematic diagram of the phase change thermal storage module in the thermal storage and release device of the present invention, which is applicable to cascade heat sources and off-peak electricity utilization. Figure 3 This is a schematic diagram of the working principle of the heat storage and release device of the present invention, which is applicable to cascade heat sources and off-peak electricity utilization; Figure 4 This is a numerical simulation streamline diagram of the heat storage and release device applicable to cascade heat sources and off-peak electricity utilization according to the present invention; Figure 5 This is a three-dimensional fitting diagram of the outlet temperature of the heat storage and release device of the present invention, which is applicable to cascade heat sources and off-peak electricity utilization, under different wind speeds and water speeds. Figure 6 This is a thermogram of the outlet temperature of the heat storage and release device of the present invention, applicable to cascade heat sources and off-peak electricity utilization, under different wind speeds and water speeds.

[0014] In the diagram, 1. Phase change thermal energy storage module, 2. Connecting pipe, 3. Third valve, 4. Fourth valve, 5. Shell and tube heat exchanger, 6. First valve, 7. Second valve, 8. Variable frequency blower, 9. First heat source inlet pipe, 10. Second heat source inlet pipe, 11. Exhaust pipe, 12. Heating box, 13. Outlet pipe, 14. 304 stainless steel pagoda head, 15. Graphite crucible, 16. K-type armored thermocouple, 17. Corundum tube. Detailed Implementation

[0015] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0016] Example 1 This invention is applicable to heat storage and release devices for cascaded heat sources and off-peak electricity utilization, such as... Figure 1 As shown, it includes a phase change thermal energy storage module 1 and a shell-and-tube heat exchanger 5, which are connected by pipes; Figure 2 As shown, the phase change thermal energy storage module 1 includes a heating box 12, inside which are placed multiple graphite crucibles 15, and Al-Cu-Si alloy phase change material is placed inside the graphite crucibles 15. The heating box 12 is also equipped with multiple K-type armored thermocouples 16, the number of which is the same as that of the graphite crucibles 15. One end of the K-type armored thermocouple 16 is in contact with the Al-Cu-Si alloy phase change material, and the other end extends out of the top of the heating box 12. Al-Cu-Si alloy phase change material possesses a high thermal conductivity of 84.5 W / (m·K) and a high latent heat of phase change of 460 kJ / kg, enabling efficient storage and stable release of thermal energy. Using the Al-Cu-Si alloy phase change material as a heat storage unit, graphite crucibles are placed in a staggered arrangement within the heating chamber. This arrangement effectively improves space utilization and promotes a uniform distribution of the thermal field.

[0017] The heating box 12 is equipped with a corundum tube 17, which extends out of the top of the heating box 12 and is connected to the outlet pipe 13 through a 304 stainless steel pagoda head 14. The end of the outlet pipe 13 is also connected to the connecting pipe 2, which is connected to the shell-side inlet of the shell-and-tube heat exchanger 5. The outlet pipe 13 is a high-temperature resistant silicone tube. A fourth valve 4 is provided on the connecting pipe 2, and the fourth valve 4 is close to the inlet of the shell and tube heat exchanger 5; the connecting pipe 2 is also connected to the first heat source inlet pipe 9; a third valve 3 is provided on the first heat source inlet pipe 9; The shell-side outlet of the shell-and-tube heat exchanger 5 is connected to the interior of the heating chamber 12 via an exhaust pipe 11. The exhaust pipe 11 is a steel pipe, and its end extends into the central furnace chamber inside the heating chamber 12. A variable frequency blower 8 is installed on the exhaust pipe 11, and a second valve 7 is installed on the exhaust pipe 11. The second valve 7 is located near the shell-and-tube heat exchanger 5. The exhaust pipe 11 is also connected to the second heat source inlet pipe 10. A first valve 6 is installed on the second heat source inlet pipe 10. The tube side of the shell-and-tube heat exchanger consists of a dense bundle of copper tubes to significantly expand the heat exchange area. Baffles are arranged inside the shell-and-tube heat exchanger as key elements for flow and enhanced heat transfer. These baffles force the airflow field to generate a continuous "S"-shaped tortuous motion, which not only effectively prolongs the residence time of the medium in the heat exchanger, but more importantly, induces a strong turbulence effect.

[0018] The heat storage and release device of the present invention effectively resists the influence of high temperature environment, ensures that high temperature air can be stably transported in the complex flow channel from the phase change heat storage module to the shell and tube heat exchanger, and eliminates leakage and damage caused by material failure or loose connection, providing a solid guarantee for the continuity and sealing of the entire thermal cycle.

[0019] Example 2 The phase change thermal energy storage module of this invention uses a high-temperature phase change material held in a graphite crucible as the thermal energy storage unit for heat storage. The phase change material is a eutectic alloy with a mass ratio of Al-25%Cu-6%Si. This alloy exhibits optimal energy storage performance in the temperature range of 508℃ to 548℃, and its phase change enthalpy is 381.26±15.00J / g. Furthermore, this alloy does not react with alumina or the graphite crucible at 600℃, allowing it to be stored in a graphite crucible. To improve the uniformity of melting and solidification of the phase change material, multiple graphite crucibles are arranged in a staggered manner within the heating chamber to improve the thermal field distribution. The main physical properties of the thermal energy storage unit are shown in Table 1.

[0020] Table 1 Main Design Parameters of the Thermal Storage Unit

[0021] A K-type armored thermocouple is used to monitor the temperature of the aluminum-based metal phase change material in the graphite crucible in real time, ensuring the precise control of the thermal management process.

[0022] Example 3 The working principle diagram of a heat storage and release device suitable for cascade heat sources and off-peak electricity utilization is as follows: Figure 3 As shown, the high-temperature air from the phase change thermal storage module enters the shell-and-tube heat exchanger through the connecting pipe. The shell-and-tube heat exchanger significantly enhances the turbulence intensity of the gas and prolongs the gas residence time, thereby greatly improving the heat exchange efficiency and temperature uniformity.

[0023] Numerical simulation streamline diagram of heat storage and release devices suitable for cascaded heat sources and off-peak electricity utilization is shown below. Figure 4 As shown in the figure, the air flows through the pipe in sequence through the shell-and-tube heat exchanger and the phase change heat storage module, where it exchanges heat with the water flowing in the shell side and the high-temperature heat source in the heat storage unit, respectively.

[0024] Example 4 Figure 5 Three-dimensional response surface plot of outlet temperature under different wind speeds and water velocities during the heat exchange process of a heat storage and release device suitable for cascade heat sources and off-peak electricity utilization; Figure 6This is a thermogram of the outlet temperature of the device of the present invention under different wind speeds and water velocities. Through analysis, the optimal parameter combination that keeps the water outlet temperature constant can be identified. This method effectively reveals the coupling relationship between operating parameters and can provide a clear decision-making basis for achieving stable system operation.

[0025] Example 5 This invention is applicable to the heat storage and release method for cascaded heat sources and off-peak electricity utilization, and is implemented using the aforementioned heat storage and release device, specifically according to the following steps: Step 1: Perform thermal storage on phase change thermal storage module 1; The heating process of phase change thermal storage module 1 mainly relies on the coordinated energy supply of cascaded heat sources and off-peak electricity. During the heating process, the temperature change of the phase change material is monitored in real time by K-type armored thermocouples 16 arranged in the thermal storage unit, accurately obtaining its temperature rise and phase change state. Given the accurate mass of the phase change material, its specific heat capacity, latent heat of phase change, and other thermophysical properties can be combined with thermodynamic calculation formulas to quantitatively analyze and obtain the actual heat storage capacity of the thermal storage unit under the current operating conditions, thereby providing reliable data support for system energy management and operation optimization.

[0026] Assuming the initial phase change thermal storage module 1 and the air temperature are both T1, the thermal storage process can be divided into three stages: (1) When the heat source is hot water and the water temperature is T water,1 When the temperature exceeds 80℃, hot water is introduced into the shell-and-tube heat exchanger 5, and the fourth valve 4 and the second valve 7 are opened. At this time, the variable frequency blower 8 is turned on, and ambient temperature air T is introduced. air,1 The air enters the shell-and-tube heat exchanger 5 and exchanges heat with the high-temperature hot water in the tube side. When the temperature difference between the air and water in the shell-and-tube heat exchanger 5 is less than 12°C, the fourth valve 4 and the second valve 7 are closed, and the phase change heat storage module 1 completes the initial heating and the temperature rises to T2.

[0027] (2) A high-temperature air heat source is used and the gas temperature T a2 If the temperature is above 80℃, based on the previous step, simultaneously open the third valve 3 and the first valve 6, close the fourth valve 4 and the second valve 7, switch to the air-based heating mode, and further heat the heat storage unit, i.e., the Al-Cu-Si alloy phase change material. When the temperature difference between the air in the phase change heat storage module 1 and the heat storage unit is less than 12℃, the phase change heat storage module 1 completes heating, the temperature rises to T3, and the third valve 3 and the first valve 6 are closed. (3) When the power system enters the off-peak electricity price period, start the heating box 12 to heat the Al-Cu-Si alloy phase change material to the target temperature T4, and the heat storage process can be completed. In the whole process, all input energy, including hot water, hot air and electrical energy, is ultimately stored in the heat storage unit in the form of heat energy.

[0028] If there is currently no waste heat available, the preheating stages of hot water and hot air will be skipped, and the thermal storage unit will be heated from its initial state to the target temperature T4 entirely using off-peak electricity during off-peak hours. A flow chart of the thermal storage experimental device for cascaded heat sources and off-peak electricity utilization is shown below. Figure 3 As shown in Part I, the entire process transfers thermal and electrical energy to the phase change thermal energy storage module.

[0029] Step 2: Release heat from phase change thermal storage module 1; During the heat release process, the fourth valve 4 and the second valve 7 are opened, and flowing air is introduced into the phase change heat storage module 1 through the variable frequency blower 8. At the same time, room temperature water with a set flow rate is injected into the tube side of the shell and tube heat exchanger 5. The air and room temperature water exchange heat in the shell and tube heat exchanger 5. The air flow rate is changed by adjusting the variable frequency blower 8, and the flow rate of room temperature water is adjusted synchronously. According to the fitting formula (1), the final outlet water temperature is obtained, thereby achieving precise control of the heat release process.

[0030] (1) In the formula, x is the flow rate of water at room temperature, in kg / h; y is the air flow rate of the variable frequency blower, in kg / h; and z is the outlet water temperature, in °C.

[0031] Example 6 The fitting formula of this invention is obtained by fitting the initial temperature and the temperature after heat release of the Al-Cu-Si alloy phase change material, the air inlet and outlet temperatures of the heat storage, the air flow rate, and the water flow rate and temperature. Figure 6 The calculated air volume and wind speed, and the given fitting formula with a determination coefficient R=0.98, indicate that the model has extremely high fitting accuracy for coupled data and can reliably describe the variation law of outlet water temperature under the combined effect of air velocity and water inlet velocity. This provides a powerful quantitative tool for system performance prediction and optimization in multi-parameter coupled scenarios.

[0032] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention, and no reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A heat storage and release device suitable for cascaded heat sources and off-peak electricity utilization, characterized in that, The device includes a phase change thermal storage module (1) and a shell-and-tube heat exchanger (5). The phase change thermal storage module (1) includes a heating box (12). Multiple graphite crucibles (15) are placed inside the heating box (12). Phase change materials are placed inside the graphite crucibles (15). A corundum tube (17) is installed inside the heating box (12). The corundum tube (17) extends out of the top of the heating box (12) and its extended end is connected to an exhaust pipe (13). The end of the exhaust pipe (13) is also connected to a connecting pipe (2). The connecting pipe (2) is connected to the shell-side inlet of the shell-and-tube heat exchanger (5). The shell-side outlet of the shell-and-tube heat exchanger (5) is connected to the interior of the heating box (12) through an exhaust pipe (11). A variable frequency blower (8) is installed on the exhaust pipe (11).

2. The heat storage and release device suitable for cascaded heat sources and off-peak electricity utilization as described in claim 1, characterized in that, The exhaust pipe (11) is provided with a second valve (7); the exhaust pipe (11) is also connected to the second heat source inlet pipe (10); the second heat source inlet pipe (10) is provided with a first valve (6).

3. The heat storage and release device suitable for cascaded heat sources and off-peak electricity utilization as described in claim 2, characterized in that, The connecting pipe (2) is provided with a fourth valve (4), and the connecting pipe (2) is also connected to the first heat source inlet pipe (9); the first heat source inlet pipe (9) is provided with a third valve (3).

4. The heat storage and release device suitable for cascaded heat sources and off-peak electricity utilization as described in claim 1, characterized in that, The heating box (12) is also equipped with a number of K-type armored thermocouples (16). One end of the K-type armored thermocouple (16) is in contact with the phase change material, and the other end extends out of the top of the heating box (12).

5. The heat storage and release device suitable for cascaded heat sources and off-peak electricity utilization as described in claim 1, characterized in that, The phase change material is an Al-Cu-Si alloy.

6. The heat storage and release device suitable for cascaded heat sources and off-peak electricity utilization as described in claim 1, characterized in that, The vent pipe (13) and the corundum pipe (17) are connected by a 304 stainless steel pagoda head (14).

7. A heat storage and release method suitable for cascaded heat sources and off-peak electricity utilization, implemented using the heat storage and release device as described in claim 3, characterized in that, The specific steps are as follows: Step 1: Heat storage in phase change thermal storage module (1): The heating process of phase change thermal storage module (1) is achieved through shell-and-tube heat exchanger (5), heat source and valley electricity co-supply; Step 2: Heat release from the phase change thermal storage module (1): During the heat release process, open the fourth valve (4) and the second valve (7), and introduce flowing air into the phase change thermal storage module (1) through the variable frequency blower (8). At the same time, inject room temperature water into the tube side of the shell and tube heat exchanger (5). The air and room temperature water exchange heat in the shell and tube heat exchanger (5). Change the air flow rate by adjusting the variable frequency blower (8) and adjust the flow rate of room temperature water simultaneously. Use the fitting formula to obtain the final outlet water temperature.

8. The heat storage and release method applicable to cascaded heat sources and off-peak electricity utilization as described in claim 7, characterized in that, In step 1, specifically: When the heat source is hot water with a temperature higher than 80°C, the hot water is introduced into the shell-and-tube heat exchanger (5), and the fourth valve (4) and the second valve (7) are opened. At this time, the variable frequency blower (8) is turned on, and the air enters the shell-and-tube heat exchanger (5) to exchange heat with the hot water on the shell side. When the temperature difference between the air and the hot water in the shell-and-tube heat exchanger (5) is less than 12°C, the fourth valve (4) and the second valve (7) are closed, and the phase change heat storage module (1) completes the initial heating and the temperature rises to T2. Using a high-temperature air heat source with a gas temperature higher than 80°C, based on the previous step, simultaneously open the third valve (3) and the first valve (6), close the fourth valve (4) and the second valve (7), switch to the air-based heating mode, and heat the phase change material. When the temperature difference between the air and the phase change material in the phase change heat storage module (1) is less than 12°C, the phase change heat storage module (1) completes the heating and the temperature rises to T3. Then, close the third valve (3) and the first valve (6). When the power system enters the off-peak electricity price period, start the heating box (12) to heat the phase change material to the target temperature T4, and the heat storage process is completed.

9. The heat storage and release method applicable to cascaded heat sources and off-peak electricity utilization as described in claim 7, characterized in that, The fitting formula is shown in equation (1): （1） In the formula, x is the flow rate of room temperature water, in kg / h; y is the air flow rate of the variable frequency blower (8), in kg / h; z represents the outlet water temperature, in °C.

Images