Multistage pressure fluctuation suppression system based on solid waste heat storage unit

Abstract

The invention provides a multi-stage pressure fluctuation suppression system based on a solid waste heat storage unit, belongs to the technical field of industrial energy conservation, and can at least partially solve the problems that in the prior art, when multi-stage pressure fluctuation is caused, an effective pressure suppression mechanism is lacked, so that the system operation stability is insufficient, especially when the load is rapidly changed, the pressure fluctuation is large, and the energy consumption is low. The heat storage unit comprises a heat storage unit body of a porous laminated body structure, and the heat storage unit body is provided with a heat storage body module, a spiral flow channel, a steam inlet pipeline, a steam outlet pipeline and a fused salt pipeline. Steam flow impact can be effectively dispersed, and flow field pressure distribution can be balanced; the heat storage body module with a high specific surface area and a high porosity honeycomb structure is adopted, the heat exchange efficiency can be enhanced, and the loose structure is used for storing a large amount of air inside to relieve the influence of external environment change on the wall of the heat storage tank.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of industrial energy saving, and particularly relates to a multi-stage pressure fluctuation suppression system based on a solid waste-based heat storage unit. BACKGROUND

[0002] In the field of industrial energy saving, as described in patents CN206309538U and CN108612634A, a multi-energy complementary heat power generation device combines solar energy, wind energy and fossil energy to achieve complementary energy supply for power generation. The device adopts a mixed heat storage technology of high-temperature liquid heat transfer medium and solid heat storage medium, and a new heat storage technology of two tanks or a single tank, aiming to simplify the structure, reduce the cost, extend the power generation time, expand the use range, improve the utilization rate of power generation equipment, and reduce the hardware investment.

[0003] However, the above technical solutions lack effective pressure suppression mechanisms when facing multi-stage pressure fluctuations, resulting in insufficient system operation stability, especially when the load changes rapidly, the pressure fluctuates greatly, affecting the system safety and efficiency. Therefore, we propose a multi-stage pressure fluctuation suppression system based on a solid waste-based heat storage unit. SUMMARY

[0004] The present application aims to at least solve one of the technical problems existing in the prior art, and provides a multi-stage pressure fluctuation suppression system based on a solid waste-based heat storage unit.

[0005] The present application provides a multi-stage pressure fluctuation suppression system based on a solid waste-based heat storage unit, comprising a heat storage unit body, which is a porous layer structure, and the heat storage unit body is provided with: a heat storage body module, comprising a plurality of heat storage bodies stacked inside the heat storage unit body; a spiral flow channel arranged inside the heat storage unit body, and the fluid inlet end of the spiral flow channel is connected with the output port of the steam inlet pipeline, so as to prolong the residence time of steam in the heat storage unit body during operation; the steam inlet pipeline, the input port of the steam inlet pipeline is connected with the steam generator; a steam outlet pipeline connected with the fluid outlet end of the spiral flow channel; and a molten salt pipeline connected with the lower end of the heat storage body module, for transporting molten salt to the pores between the heat storage body modules during operation.

[0006] Further, the porosity of the heat storage unit body is 0.6-0.8, and the heat storage unit body includes at least two heat storage body modules.

[0007] Specifically, the steam inlet pipeline is connected with a dynamic pressure regulating module, the dynamic pressure regulating module is electrically connected with a first pressure sensor arranged on the steam inlet pipeline, a second pressure sensor arranged in the middle of the heat storage unit body, a third pressure sensor arranged on the steam outlet pipeline, and a safety protection system, the safety protection system comprises a double-redundancy electromagnetic pressure relief valve and a mechanical safety valve.

[0008] Specifically, the molten salt pipeline transports NaNO-KNO eutectic salt.

[0009] Preferably, a molten salt pump and a valve assembly are arranged on the molten salt pipeline, the valve assembly comprises a main valve and a backup valve, and the main valve and the backup valve are both electric three-way valves.

[0010] Specifically, the spiral flow channel is a cross-back spiral flow channel, the opening diameter of the spiral flow channel ranges from 1mm to 10mm, the depth of the spiral flow channel ranges from 1mm to 10mm, the height of the spiral flow channel ranges from 1mm to 10mm, and the spiral angle of the spiral flow channel ranges from 30° to 90°.

[0011] Further, a flow direction adjusting valve is arranged on the spiral flow channel, and the flow direction adjusting valve is one of a needle valve, a ball valve and a gate valve.

[0012] Further, a heat exchanger is arranged at the upper end of the heat storage unit body, and the heat exchanger is connected with the upper end pipeline of the heat storage body module, so as to realize heat exchange between the steam and the molten salt during operation.

[0013] Further, a dense layer is arranged on the surface of the heat storage unit body, the thickness of the dense layer ranges from 0.5mm to 1mm, and a support base is arranged at the lower end of the heat storage unit body, and the support base is connected and fixed with the heat storage unit body through a flange.

[0014] Specifically, the heat storage body module is a porous structure, the shape of the heat storage body module is one of a cylinder, a sphere or a cube, the material of the heat storage body module is one of fly ash, ceramic, P92 steel and 316L stainless steel, the porosity of the heat storage body module is greater than or equal to 70%, the thermal conductivity of the heat storage body module is greater than or equal to 30W / (m·K), and the volumetric heat capacity of the heat storage body module is greater than or equal to 150J / (kg·K).

[0015] The beneficial effects of the present application are as follows: By setting a spiral flow channel in the heat storage unit, the steam flow impact can be effectively dispersed, and the flow field pressure distribution is balanced; the synergistic effect of the dynamic pressure regulating module and the multi-point pressure sensor can monitor and regulate the pressure fluctuation in the heat storage unit in real time, thereby improving the operation stability and safety of the system; the high specific surface area and high porosity honeycomb structure made of microporous ceramics prepared from industrial solid waste can greatly enhance the heat exchange efficiency and store a large amount of air in the loose structure to slow down the influence of external environmental changes on the heat storage tank wall; the eutectic salt NaNO-KNO as a phase change material is used to actively regulate the temperature field in the heat storage unit. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 Figure 1 is a connection diagram of a specific embodiment of a multi-stage pressure fluctuation suppression system based on a solid waste-based heat storage unit of the present application; Figure 2 Figure 2 is an internal structure diagram of a heat storage unit main body of a specific embodiment of a multi-stage pressure fluctuation suppression system based on a solid waste-based heat storage unit of the present application.

[0017] Among them, 1 is a steam inlet pipeline, 2 is a heat exchanger, 3 is a support base, 4 is a valve assembly, 5 is a steam outlet pipeline, 6 is a heat storage unit main body, 7 is a flow direction regulating valve, 8 is a spiral flow channel, and 9 is a heat storage body module. DETAILED DESCRIPTION

[0018] In order for those skilled in the art to better understand the technical solutions of the present application, the present application will be further described in detail below in conjunction with the drawings and specific embodiments.

[0019] As shown in Figure 1 The specific embodiment of the present application provides a multi-stage pressure fluctuation suppression system based on a solid waste-based heat storage unit, which comprises a heat storage unit main body. The heat storage unit main body is a porous laminated body structure. The heat storage unit main body is provided with: a heat storage body module, comprising a plurality of heat storage bodies laminated in the interior of the heat storage unit main body; a spiral flow channel, which is arranged in the interior of the heat storage unit main body, and the fluid inlet end of the spiral flow channel is connected with the output port of the steam inlet pipeline, so as to prolong the residence time of steam in the heat storage unit main body during operation; a steam inlet pipeline, the input port of which is connected with a steam generator; a steam outlet pipeline, which is connected with the fluid outlet end of the spiral flow channel; and a molten salt pipeline, which is connected with the lower end of the heat storage body module, so as to transport molten salt to the pores between the heat storage body modules during operation.

[0020] Specifically, the porosity of the heat storage unit main body 6 is 0.6-0.8, and the interior of the heat storage unit main body 6 comprises at least two heat storage body modules 9.

[0021] Further, the heat storage unit body 6 serves as a shell and core bearing structure of the whole system, and internally contains the heat storage body module 9, the spiral flow channel 8 and the flow direction adjusting valve 7; the inlet steam enters from the external steam generator, is guided to the inside of the heat storage unit body 6 through the inlet, and exchanges heat with the heat storage body module 9.

[0022] Further, the manufacturing steps of the heat storage body module 9 include microporous blank manufacturing, blank glue removal, granulation, pre-burning, molten salt immersion and high-temperature sintering; the microporous blank is prepared by using a self-propagating combustion synthesis technology (SHS), and includes two phases of a-AlO and β-AlO; the microporous blank prepared by the SHS method is ground after pre-burning at 600-800 ℃; the ground microporous blank is granulated by adding a binder, and is pre-burned again at 500-700 ℃ for 3-5 hours to obtain a dry microporous blank; the dry microporous blank is placed in molten NaNO-KNO eutectic salt for immersion treatment, and then is sintered at 1200-1600 ℃ for 8-12 hours to obtain a porous heat storage body module.

[0023] On the basis of the above basic embodiment, the steam inlet pipeline 1 is connected with a dynamic pressure regulating module, the dynamic pressure regulating module is electrically connected with a first pressure sensor arranged in the steam inlet pipeline 1, a second pressure sensor arranged in the middle of the heat storage unit body 6, a third pressure sensor arranged in the steam outlet pipeline 5, and a safety protection system, and the safety protection system includes a double-redundancy electromagnetic pressure relief valve and a mechanical safety valve.

[0024] Specifically, the safety protection system is electrically connected with the first pressure sensor and the second pressure sensor, and automatically relieves pressure when the pressure exceeds a threshold value.

[0025] In one specific embodiment, the molten salt is a NaNO-KNO eutectic salt formed by mixing sodium nitrate and potassium nitrate in a certain proportion and cooling after being heated and molten.

[0026] In the embodiment, a molten salt pump and a valve assembly 4 are arranged on the molten salt pipeline, the valve assembly 4 includes a main valve and a standby valve, and the main valve and the standby valve are both electrically-controlled three-way valves; the valve assembly is respectively connected with the first pressure sensor, the second pressure sensor and the third pressure sensor, and the three sensors have a mutual backup function.

[0027] Further, the phase change temperature and the latent heat of the molten salt are 139 ℃ and 300 kJ / kg, respectively.

[0028] In another specific embodiment, the spiral channel 8 is a cross-loop spiral channel. The opening diameter of the spiral channel ranges from 1 mm to 10 mm, the depth ranges from 1 mm to 10 mm, the height ranges from 1 mm to 10 mm, and the spiral angle ranges from 30° to 90°. The depth range refers to the maximum vertical distance from the opening to the bottom of the spiral channel on a cross section perpendicular to its flow direction. The height range refers to the overall axial height of the spiral channel, that is, the total projected height in the axial direction from the spiral starting point to the ending point.

[0029] Specifically, a flow direction regulating valve 7 is installed on the spiral flow channel. The flow direction regulating valve 7 is one of the needle valve, ball valve, and gate valve. The flow channel arrangement of the cross-loop spiral flow channel is as follows: a spiral direction is formed in the longitudinal direction; staggered "U-shaped" channels are designed in the radial or vertical direction to form intersections; the overall structure is similar to a three-dimensional network of "spiral + U-shaped intersection"; after the fluid enters from the inlet, it moves along the spiral trajectory and is guided to another layer or another side return channel at a local position, intersecting with the original flow direction, and then continues to move forward; the channels intersect at different heights and angles, similar to a staggered double spiral but with U-shaped reversals.

[0030] In one specific embodiment, a heat exchanger 2 is provided at the upper end of the main body 6 of the heat storage unit. The heat exchanger 2 is connected to the heat storage module 9 by pipeline to realize heat exchange between steam and molten salt during operation.

[0031] In this embodiment, the upper end of the heat storage module 9 is connected to the heat exchanger, and the molten salt and steam circulate for heat exchange to complete the heat transfer.

[0032] Specifically, an auxiliary heating device is installed at one end of the molten salt pipeline to supplement the heating of the molten salt when the external heat is insufficient, so as to ensure the working temperature of the heat storage unit.

[0033] In another specific embodiment, a dense layer is provided on the surface of the thermal storage unit body 6, the thickness of which is 0.5mm to 1mm. A support base 3 is provided at the lower end of the thermal storage unit body 6, and the support base 3 is connected and fixed to the thermal storage unit body 6 through a flange. The dense layer provided on the thermal storage unit body 6 provides structural sealing and thermal insulation, prevents leakage, and controls the direction of heat flow.

[0034] Furthermore, the thermal storage module 9 has a three-dimensional porous structure, and its shape is one of a cylinder, a sphere, or a cube. The material of the thermal storage module 9 is one of fly ash, ceramic, P92 steel, or 316L stainless steel. The porosity of the thermal storage module 9 is ≥70%, the thermal conductivity of the thermal storage module 9 is ≥30W / (m·K), and the volumetric specific heat capacity of the thermal storage module 9 is ≥150J / (kg·K).

[0035] Further, the operation method of the system comprises: S1. Load reduction period, system steady state condition: during stable operation, the steam pressure shows an upward trend due to the reduction of the unit load; S2. Sensor detection, pressure recovery: the first pressure sensor is used to monitor the inlet pressure in real time, and when the set value is reached, a signal is sent to the control system; S3. Closed-loop control, steam supplement: at this time, the steam intake is less than the steam outlet, and the pressure in the container begins to rise. The signal detected by the second pressure sensor is fed back to the dynamic adjustment module, which adjusts the opening frequency of the molten salt pump to speed up the salt absorption speed, supplements the evaporation gap, and restores the system pressure balance; S4. High load supplement: as the load increases again, the outlet pressure exceeds the standard again, S5. Safety protection, steam pressure reduction: at this time, the third pressure sensor receives an over-standard signal, sends an alarm and a signal to the control system, opens the safety relief valve to reduce the gas supply pressure, and if the fluctuation still cannot be suppressed, opens the standby relief valve to ensure the normal operation of the equipment is not affected; S6. Auxiliary heating, vapor-liquid separation: when the external load continues to run at a high level, the phase change material gradually solidifies and releases heat to maintain the uniformity and constancy of the temperature field in the tank; S7. Molten salt water supplement: when the NaNO-KNO eutectic salt content in the system decreases, the molten salt water supplement pump is started in time to supplement water; The LADRC algorithm is introduced into the complex multivariable PVT gas-liquid coupling system to realize accurate time domain control of the internal multivariable energy flow; LADRC is mainly embedded in the dynamic pressure regulating module and the control system as the core algorithm to replace or enhance the traditional feedback control; Hardware basis: use the existing pressure sensor components deployed at the steam inlet pipeline, the middle part and the outlet to provide real-time multivariable data, including pressure as the main variable, indirectly reflecting temperature and volume changes, molten salt pump, flow direction regulating valve 7, valve assembly and safety protection system as actuators.

[0036] Software integration: Multivariable decoupling design: Decentralized LADRC structure is adopted, and independent LADRC controllers are allocated for each key variable (such as inlet pressure, middle pressure, outlet pressure and molten salt temperature); The controllers are coupled through cross feedback processing.

[0037] Algorithm embedding position: dynamic pressure regulating module: as the main control center, running LADRC algorithm. Input: sensor signal (S2, S3, S5); output: control signal to molten salt pump (adjusting frequency / speed) and valve (opening degree); closed loop: integrated with operation method S3 / S5, forming a feedback loop: sensor→LADRC (estimating disturbance)→actuator→system state update; safety linkage: LADRC output triggers the safety protection system (S5) if it fails to suppress the disturbance, such as opening the pressure relief valve; parameter tuning: based on system parameters (such as the porosity of the heat storage module 9≥70%, the size of the spiral flow channel 8), the parameters are simulated. The observer bandwidth is set to 3~5 times the dominant frequency of the system to ensure fast disturbance estimation; the controller bandwidth is set according to the response time (such as the pressure recovery needs to be in seconds).

[0038] In order to help better understand the present application, a more comprehensive and specific embodiment of the present application is described, in which the present application provides a multi-stage pressure fluctuation suppression system based on solid waste-based heat storage unit, including a heat storage unit body 6 of a porous layer stack structure, which is provided with: a heat storage module 9, which is stacked inside the heat storage unit body 6; a spiral flow channel 8, which is arranged inside the heat storage unit body 6, and the fluid inlet end of the spiral flow channel is connected with the steam inlet pipeline 1, so as to prolong the residence time of the steam in the heat storage unit body 6 during operation; a steam inlet pipeline 1, one end of which away from the heat storage unit body 6 is connected with a steam generator; a steam outlet pipeline 5 connected with the fluid outlet end of the spiral flow channel 8; and a molten salt pipeline connected with the lower end of the heat storage module 9, for conveying molten salt to the pores of the heat storage module 9 during operation.

[0039] In the embodiment, the porosity of the heat storage unit body 6 is 0.6-0.8, the heat storage unit body 6 internally includes at least two heat storage modules 9; the steam inlet pipeline 1 is connected with a dynamic pressure regulating module, the dynamic pressure regulating module is electrically connected with a first pressure sensor arranged on the steam inlet pipeline 1, a second pressure sensor arranged in the middle of the heat storage unit body, a third pressure sensor arranged on the steam outlet pipeline 5, and a safety protection system, the safety protection system includes a double-redundancy electromagnetic pressure relief valve and a mechanical safety valve; the molten salt is a NaNO-KNO eutectic salt formed by mixing sodium nitrate and potassium nitrate in proportion and cooling after heating and melting; a molten salt pump and a valve assembly 4 are arranged on the molten salt pipeline, the valve assembly 4 includes a main valve and a standby valve, and the main valve and the standby valve are both electric three-way valves; the spiral flow channel 8 is a cross-back spiral flow channel, the opening diameter of the spiral flow channel 8 ranges from 1mm to 10mm, the depth of the spiral flow channel 8 ranges from 1mm to 10mm, the height of the spiral flow channel 8 ranges from 1mm to 10mm, and the spiral angle of the spiral flow channel 8 ranges from 30° to 90°; a flow direction adjusting valve 7 is arranged on the spiral flow channel 8, and the flow direction adjusting valve 7 is one of a needle valve, a ball valve and a gate valve; a heat exchanger 2 is arranged at the upper end of the heat storage unit body 6, the heat exchanger 2 is connected with the pipeline of the heat storage module 9, so as to realize heat exchange between steam and molten salt during operation; a dense layer is arranged on the surface of the heat storage unit body 6, the thickness of the dense layer is 0.5mm-1mm, and a support base 3 is arranged at the lower end of the heat storage unit body 6, and the support base 3 is connected and fixed with the heat storage unit body 6 through a flange.

[0040] Further, the heat storage module 9 is a three-dimensional porous structure, the shape of the heat storage module 9 is one of a cylinder, a sphere or a cube, the material of the heat storage module 9 is one of fly ash, ceramic, P92 steel and 316L stainless steel, the porosity of the heat storage module 9 is greater than or equal to 70%, the thermal conductivity of the heat storage module 9 is greater than or equal to 30W / (m·K), and the volumetric heat capacity of the heat storage module 9 is greater than or equal to 150J / (kg·K).

[0041] In summary, the embodiment of the present disclosure has at least the following technical effects: High efficient pressure fluctuation suppression capability: By arranging the spiral flow channel 8 and the flow direction adjusting valve 7 in the heat storage unit, the steam flow impact can be effectively dispersed, and the flow field pressure distribution is balanced; the dynamic pressure regulating module and the multiple-point pressure sensor can cooperate to realize real-time monitoring and regulation of the pressure fluctuation in the heat storage unit, and the operation stability and safety of the system are improved; Excellent heat exchange and heat storage performance: The heat storage body module 9 is prepared from solid waste-based porous ceramics such as fly ash and steel slag, has a porosity of ≥70% and a high thermal conductivity, and significantly improves the heat exchange efficiency of steam and molten salt; the porous layer stack structure is combined with a phase change material to realize coupled heat storage of sensible heat and latent heat, and improve the heat storage capacity per unit volume and energy utilization rate; Enhanced safety and reliability: Three pressure sensors are distributed at the steam inlet pipeline, the middle part and the outlet position to form redundant detection, ensuring the accuracy and reliability of data monitoring; the valve assembly 4 adopts a main valve + backup valve design, and is provided with double-redundancy electromagnetic relief valves and mechanical safety valves, which can quickly relieve pressure under abnormal working conditions to prevent overpressure failure; Optimized structure and strong controllability: The cross-back design of the spiral flow channel 8 realizes a controllable flow path, so that the residence time of the fluid in the heat storage unit is more uniform, and the heat exchange is more sufficient; the flow direction adjusting valve 7 can flexibly adjust the flow and flow rate according to the actual working condition, and is suitable for different loads and pressure conditions; Multifunctional integration and high adaptability: The system has the functions of heat storage, heat exchange and pressure stabilization, and can be applied in power station steam circulation, industrial waste heat recovery, energy storage peak shaving and other scenes; the modular design of the porous layer stack facilitates scale expansion and maintenance and replacement.

[0042] It can be understood that the above embodiments are only exemplary embodiments for illustrating the principles of the present application, but the present application is not limited thereto. Various modifications and improvements can be made by those skilled in the art without departing from the spirit and essence of the present application, and these modifications and improvements are also considered to be within the protection scope of the present application.

Claims

1. A multi-stage pressure fluctuation suppression system based on a solid waste-based thermal storage unit, characterized in that, The thermal storage unit includes a main body, which is a porous laminated structure, and the main body is provided with: A thermal storage module includes multiple thermal storage elements stacked inside the main body of the thermal storage unit; A spiral flow channel is provided inside the main body of the thermal storage unit, and the fluid inlet end of the spiral flow channel is connected to the output port of the steam inlet pipe to extend the residence time of steam in the main body of the thermal storage unit during operation. The steam inlet pipe has its input port connected to the steam generator; A steam outlet pipe is connected to the fluid outlet end of the spiral flow channel; and Molten salt pipelines are connected to the lower end of the thermal storage modules to deliver molten salt into the pores between the thermal storage modules during operation.

2. The multi-stage pressure fluctuation suppression system based on a solid waste-based thermal storage unit according to claim 1, characterized in that, The porosity of the main body of the thermal storage unit is 0.6 to 0.8, and the main body of the thermal storage unit includes at least two thermal storage modules.

3. The multi-stage pressure fluctuation suppression system based on a solid waste-based thermal storage unit according to claim 1, characterized in that, The steam inlet pipe is connected to a dynamic pressure regulating module. The dynamic pressure regulating module is electrically connected to a first pressure sensor installed on the steam inlet pipe, a second pressure sensor installed in the middle of the main body of the thermal storage unit, a third pressure sensor installed on the steam outlet pipe, and a safety protection system. The safety protection system includes a dual redundant electromagnetic pressure relief valve and a mechanical safety valve.

4. The multi-stage pressure fluctuation suppression system based on a solid waste-based thermal storage unit according to claim 1, characterized in that, The molten salt transported in the molten salt pipeline is a NaNO-KNO eutectic salt.

5. The multi-stage pressure fluctuation suppression system based on a solid waste-based thermal storage unit according to claim 1, characterized in that, The molten salt pipeline is equipped with a molten salt pump and a valve assembly. The valve assembly includes a main valve and a backup valve, both of which are electric three-way valves.

6. The multi-stage pressure fluctuation suppression system based on a solid waste-based thermal storage unit according to claim 1, characterized in that, The spiral flow channel is a cross-loop spiral flow channel. The opening diameter of the spiral flow channel ranges from 1 mm to 10 mm, the depth of the spiral flow channel ranges from 1 mm to 10 mm, the height of the spiral flow channel ranges from 1 mm to 10 mm, and the spiral angle of the spiral flow channel ranges from 30° to 90°.

7. The multi-stage pressure fluctuation suppression system based on a solid waste-based thermal storage unit according to claim 6, characterized in that, The spiral flow channel is equipped with a flow direction regulating valve, which is one of a needle valve, a ball valve, or a gate valve.

8. The multi-stage pressure fluctuation suppression system based on a solid waste-based thermal storage unit according to claim 1, characterized in that, A heat exchanger is provided at the upper end of the main body of the thermal storage unit. The heat exchanger is connected to the upper pipeline of the thermal storage module to realize heat exchange between the steam and the molten salt during operation.

9. The multi-stage pressure fluctuation suppression system based on a solid waste-based thermal storage unit according to claim 1, characterized in that, The surface of the main body of the thermal storage unit is provided with a dense layer with a thickness of 0.5mm to 1mm. A support base is provided at the lower end of the main body of the thermal storage unit, and the support base is connected and fixed to the main body of the thermal storage unit through a flange.

10. The multi-stage pressure fluctuation suppression system based on a solid waste-based thermal storage unit according to any one of claims 1 to 9, characterized in that, The thermal storage module has a porous structure and is shaped as a cylinder, sphere, or cube. The material of the thermal storage module is one of fly ash, ceramic, P92 steel, or 316L stainless steel. The porosity of the thermal storage module is ≥70%, the thermal conductivity is ≥30W / (m·K), and the volumetric specific heat capacity is ≥150J / (kg·K).

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