A heat storage unit using rough stones to store heat energy and a heat storage system formed thereby
Patent Information
- Application Number
- CN202521284893.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-23
- Publication Date
- 2026-10-09
- Estimated Expiration
- 2035-06-23
AI Technical Summary
[0003]鉴于上述技术需求，本身用新型的目的在于提供一种利用毛石存储热能的装置及连接结构，其目的在于解决毛石不符合作为蓄热体的使用要求，现有设备没有充分利用蓄热体、制造成本高这方面存在的问题
[0020]本身用新型所采用的技术方案具有以下优点：
Smart Images
Figure CN224838604U_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of high-temperature steam thermal energy storage technology, specifically to a thermal energy storage unit and system that utilizes rubble to store thermal energy, which is more stable, efficient, and economical in steam thermal energy storage technology. Background Technology
[0002] Currently, the combined power generation capacity of wind and solar power in China is approaching the installed capacity of thermal power plant generator units. However, due to the significant fluctuations in power generation capacity caused by weather, the stable operation of the power grid still relies on the power generation capacity of thermal power plants. To improve the grid connection rate of wind and solar power, thermal power plants often operate at lower power output. In this state, the steam turbine cannot fully consume the steam provided by the coal-fired boiler. To store the excess steam, reduce energy waste, and lower the operating costs of thermal power plants, many plants have utilized existing thermal storage technologies to store steam heat energy. Examples include equipment using molten salt tanks or thermal storage devices made from processed stone slabs or granules. A common challenge is the high cost of the thermal storage materials, making it difficult to recoup the investment within five years. If rubble is used to replace the existing thermal storage materials, its irregular shape does not meet the requirements for use as a thermal storage medium. Steam heat storage and release is a process of cooling and depressurizing the steam heat source. Current technologies generally use a single heat storage insulated shell with a steam heat exchanger installed within a large temperature range to collect and store heat. The temperature stored in the heat storage body is the energy integral value distributed across the input steam temperature range. Some devices use multiple heat exchangers to collect heat and multiple heat storage bodies to store it. However, in these devices, the heat storage bodies at different temperatures do not use independent closed circulation channels or incompletely independent insulated shells. This leads to the phenomenon of heat energy transfer from the higher-temperature heat storage body to the lower-temperature heat storage body, resulting in inefficient use of the heat storage body and increased manufacturing costs. Therefore, it is necessary to research a technical solution that can improve the heat storage capacity of the equipment, reduce the cost of heat storage materials, shorten the investment payback period, accelerate the promotion of steam thermal energy storage equipment in coal-fired power plants, achieve thermal and electrical decoupling in power plants, and reduce energy waste during power plant operation. Summary of the Invention
[0003] In view of the above technical requirements, the purpose of this invention is to provide a device and connection structure for storing thermal energy using rubble, in order to solve the problems that rubble does not meet the requirements for use as a heat storage medium, and that existing equipment does not make full use of the heat storage medium and has high manufacturing costs.
[0004] To achieve the above objectives, the novel invention adopts the following technical solution:
[0005] The present invention provides a heat storage unit for storing thermal energy using rubble, characterized in that: the heat storage unit consists of a heat storage tank and a heat exchanger, a fan and pipelines connected to the heat storage tank;
[0006] The heat storage tank is a barrel-shaped structure made of heat-resistant metal or heat-resistant concrete; the top of the heat storage tank is connected to the high-temperature air zone, and the bottom of the heat storage tank is connected to the low-temperature air zone; a heat exchanger is installed in the pipeline of the high-temperature air zone, and the low-temperature air zone is connected to the fan through the pipeline; the heat storage tank, the high-temperature air zone, the fan and the low-temperature air zone form a closed circulating air channel with bidirectional reversible airflow.
[0007] The heat storage tank has a heat storage layer inside, which is divided into a bottom heat storage layer, a middle heat storage layer and a top heat storage layer from bottom to top. Each heat storage layer is made of stacked rubble.
[0008] A uniform air distribution layer is provided between each heat storage layer, which is a uniform air distribution channel to balance the heat storage and heat release capacity of each heat storage layer.
[0009] The heat exchanger is equipped with a first pipe interface and a second pipe interface;
[0010] The above structures constitute a heat storage unit.
[0011] Furthermore, the number of the central heat storage layers ranges from 1 to 60.
[0012] Furthermore, the air distribution layer is constructed of strip-shaped stones, which are arranged horizontally, with air distribution gaps left between each strip-shaped stone.
[0013] Furthermore, adjacent strips of stone are placed horizontally with a 90° projection of each other.
[0014] Furthermore, the heat storage tank is equipped with an insulation layer, which is composed of aluminum silicate cotton, perlite, and refractory insulation castable.
[0015] Furthermore, the fan is an axial flow fan that can drive airflow in both forward and reverse directions.
[0016] Furthermore, in each heat storage layer, the rubble is dry-laid without binder, and shims are placed in places where the stones are tightly stacked to form air channels.
[0017] The heat storage tank is installed in sections, with each section containing a combination of 1 to 2 heat storage layers and air distribution layers.
[0018] A thermal storage system comprising a thermal storage unit utilizing rubble to store thermal energy, as described above, consists of several thermal storage units connected in series. The first pipe interface on the first thermal storage unit is connected to a high-temperature steam heat source via pipes and valves. The second pipe interface on the first thermal storage unit is connected to the first pipe interface on the second thermal storage unit. The second pipe interface on the second thermal storage unit is connected to the first pipe interface on the next thermal storage unit, and so on. The second pipe interface of the last thermal storage unit is connected to a heat release water supply system via pipes, valves, and a heat release water pump.
[0019] Furthermore, among the several heat storage units connected in series, one heat storage unit operates at the condensation temperature of the exothermic steam, forming a parallel structure. Heat storage units that operate below the condensation temperature of the steam adopt a series structure, that is: the second pipe interface of the previous heat storage unit is connected in parallel with the first pipe interface of 2 to 20 heat storage units, the second pipe interface of the 2 to 20 parallel heat storage units is connected in series with the first pipe interface of the next heat storage unit, and the second pipe interface of the last heat storage unit is connected to the exothermic water supply system through pipes, valves and exothermic water pump.
[0020] The technical solution adopted by the novel invention has the following advantages:
[0021] This technical solution involves using 600mm×600mm×30mm stone slabs with four 50mm diameter mounting holes drilled in the plane to construct and install the heat storage body. It was found that each cubic meter of stone slab costs over 2000 RMB, which translates to approximately 800 RMB per ton. For a heat storage body capable of storing 100 tons of steam at 20MPa and 560℃, 1425 cubic meters of stone slabs are required, equivalent to 3560 tons, resulting in an investment of 2.85 million RMB. If the stone slabs were replaced with 3560 tons of rubble of the same weight, costing no more than 100 RMB per ton, the investment would be 356,000 RMB. Therefore, using rubble for heat storage reduces the initial investment by 2.494 million RMB, demonstrating significant economic advantages and shortening the equipment investment payback period. The rubble stacked inside the heat storage tank... The heat exchange of the heat storage layer is carried out through the air gaps naturally formed during the masonry process. The heat storage layer is set up in layers with uniform air distribution layers, which is conducive to the uniformity of heat exchange through the air gaps of the rubble. At the same time, the air distribution gaps of the upper and lower adjacent air distribution layers are placed horizontally with 90° projections between them. This avoids the short-circuit effect caused by the straight flow of high-temperature or low-temperature air through the heat storage layer, and can better form a uniform air distribution field, so that the high-temperature or low-temperature air exchanges heat energy with the heat storage layer more evenly. By connecting multiple heat storage units in series, the heat storage work can realize the segmented storage of heat energy of superheated steam along the temperature gradient from high-temperature superheated steam temperature to low-temperature condensate temperature. The more units connected in series, the finer the temperature segmentation, the smaller the temperature loss during the heat storage process, and the higher the output parameters of steam. Attached Figure Description
[0022] Figure 1 This is a schematic diagram of the structure of the novel heat storage unit.
[0023] Figure 2 This is a top view schematic diagram of the new type of wind-equalizing layer;
[0024] Figure 3 This is a front view schematic diagram of the new type of wind uniform layer;
[0025] Figure 4 This is a schematic diagram showing the combination of novel heat storage units connected in series.
[0026] Figure 5 This is a schematic diagram of a new type of heat storage unit connected in series and parallel.
[0027] Explanation of icon numbers:
[0028] 1. Heat storage layer; 2. Air distribution layer; 2-1. Strip-shaped stone; 2-2. Air distribution gap; 3. Heat storage tank; 3-1. Inner wall of heat storage tank; 3-2. Reinforcing structure of heat storage tank; 3-3. Outer wall of heat storage tank; 3-4. Supporting ventilation structure of heat storage tank; 4. Insulation layer; 11. Heat exchanger; 12. Fan; 13. High-temperature air duct; 14. High-temperature air zone; 15. Low-temperature air duct; 16. Low-temperature air zone; 21. High-temperature steam heat source; 22. Heat storage drainage system; 23. Heat release water supply system; 24. Heat release steam user; 25. Heat storage control valve; 26. Heat release control valve; 27. Heat release water pump; 28. First pipe interface; 29. Second pipe interface; 30. High-temperature steam interface; 31. Low-temperature water interface; 100. Heat storage unit. Detailed Implementation
[0029] Exemplary embodiments of this disclosure will now be described in more detail with reference to the accompanying drawings.
[0030] This embodiment provides a heat storage unit 100 that utilizes rubble to store thermal energy. Figure 1 This is a schematic diagram of the heat storage unit 100, comprising a heat storage layer 1, an air distribution layer 2, a heat storage tank 3, a heat exchanger 11, and a fan 12. The heat storage layer 1 is located inside the heat storage tank 3 and consists of a bottom heat storage layer 1, multiple middle heat storage layers 1, and a top heat storage layer 1 from bottom to top. Each heat storage layer 1 is constructed from stacked rubble. The bottom heat storage layer 1 is located on the heat storage tank support ventilation structure 3-4, which resembles a grate in shape and function. The bottom layer is connected to the heat storage tank support ventilation structure 3-4, and the upper part is connected to the air distribution layer 2. Figure 2 , 3 As shown, the middle heat storage layer 1 is set above each wind distribution layer 2 and is isolated from each wind distribution layer 2, and is connected to the wind distribution layer 2 at the top; the top heat storage layer 1 is set above the wind distribution layer 2 and is connected to the high-temperature wind zone 14 at the top; multiple wind distribution layers 2 are set inside the heat storage tank 3, which can separate each heat storage layer 1 and are parallel to the heat storage tank support ventilation structure 3-4. They are constructed of strip-shaped stones 2-1, with wind distribution gaps 2-2 left between the strip-shaped stones 2-1. The strip-shaped stones 2-1 of adjacent wind distribution layers 2 are placed horizontally with 90° projections; the heat storage tank 3 includes the inner wall 3-1, the reinforcing structure 3-2, the outer wall 3-3, and the support ventilation structure 3-4, and is a barrel-shaped structure made of heat-resistant metal or heat-resistant concrete; the insulation layer 4 is made of aluminum silicate cotton, perlite, and refractory insulation castable, and is set on the outside of the heat storage tank 3. The heat storage unit 100 is provided with a first pipe interface 28 and a second pipe interface 29 for external connection.
[0031] From the irregularly shaped rubble obtained after rock blasting in the quarry, stones weighing between 1 kg and 20 kg are selected as the raw material for stacking the heat storage layer 1. No cement mortar or adhesives are needed to construct the heat storage layer 1. Based on the heat storage and release data of each heat storage layer 1, the size and weight of the stones in each heat storage layer 1 are adjusted according to the thermal conductivity of the selected rubble and the heat exchange temperature difference requirements of the equipment design. The ventilation interval between each rubble and the thickness of the heat storage layer 1 are adjusted according to the air pressure, flow rate, and air temperature requirements of the circulating fan 12. If the rubble stones in contact cannot form a sufficient gap for heat exchange air, shims should be placed at the contact surfaces between the rubble stones to establish this gap. Any type of shim that can stably establish a heat exchange air gap between the rubble stones can be used, including: 30mm x 30mm iron blocks made from 5mm to 10mm thick steel plate scraps, or steel bar ends with a diameter of 5mm to 10mm and a length of 50mm, etc. Rubble stones can also be made from scraps from stone processing plants as the raw material for the stacked heat storage layer 1. The installation method is simple: lay the stones layer by layer, inserting shims in denser areas to form air channels, and then lay another layer on top. Because the rubble stones are irregularly shaped, there is virtually no short-circuit effect in the air channels between each layer. Therefore, this method is low-cost, efficient, and easy to use.
[0032] The volume of the heat storage tank 3 is the product of the inner cavity plane enclosed by the inner wall 3-1 and the height of the inner cavity. It is designed based on the heat storage capacity and heat exchange temperature difference. The larger the required heat storage capacity, the larger the amount of rubble used; the smaller the designed heat exchange temperature difference, the more rubble used. The heat storage tank 3 is generally a cylindrical structure with a height not exceeding 30m and a diameter less than 8m. In special cases, it can also be made into other polygonal tank structures. The heat storage tank 3 is installed in sections, with 1-2 heat storage layers 1 and air distribution layers 2 combined in each section. During construction, one empty shell section of the heat storage tank 3 can be installed first, and then the heat storage layer 1 and air distribution layer 2 can be installed in the empty shell section of the heat storage tank 3. This operation is repeated until the high-temperature air zone 14 is installed, thus completing the heat storage tank 3; or, each empty shell section of the heat storage tank 3 can be installed on the ground first. After the heat storage layer 1 and the air distribution layer 2 are installed, the shell sections of the heat storage tank 3 are hoisted and installed in sequence. When the high-temperature air zone 14 is installed, the installation of the heat storage tank 3 is completed. Alternatively, the shell of the heat storage tank 3 can be built as a whole on the equipment foundation first, and then the heat storage tank support ventilation structure 3-4, bottom heat storage layer 1, air distribution layer 2, middle heat storage layer 1, air distribution layer 2, ... air distribution layer 2, middle heat storage layer 1, air distribution layer 2, top heat storage layer 1 are installed from bottom to top inside the shell of the heat storage tank 3. When the high-temperature air zone 14 is installed, the installation of the heat storage tank 3 is completed.
[0033] Figure 4The schematic diagram of the system, which uses a novel series-connected heat storage units, shows a combined structure consisting of multiple heat storage units 100 connected in series. The first pipe interface 28 of the first heat storage unit 100 is connected to the high-temperature steam interface 30, the second pipe interface 29 is connected to the first pipe interface 28 of the second heat storage unit 100, and so on, until the second pipe interface 29 of the last heat storage unit 100 is connected to the low-temperature water interface 31. By connecting multiple heat storage units 100 in series for heat storage, the system can store heat energy in segments along the temperature gradient from high-temperature superheated steam temperature to low-temperature condensate temperature. The more units connected in series, the finer the temperature segmentation, the smaller the temperature loss during the heat storage process, and the higher the output steam parameters. Figure 4 In addition to storing the heat energy carried by steam, series-connected thermal storage units are also suitable for storing the heat energy of high-temperature fluids such as high-temperature flue gas, hot air, heat transfer oil, and high-temperature water. In specific projects, this is more efficient than... Figure 4 , Figure 5 The connection relationships are complex, with parallel operating unit connection structures in the middle, and the connection relationships of the heat storage units will change when the heat storage and heat release working states are switched, in order to improve the utilization rate of steam thermal energy.
[0034] During the heat storage process, the heat release control valve 26 is closed and the heat storage control valve 25 is opened. The high-temperature steam heat source 21 enters the heat exchanger 11 of the first heat storage unit 100 through the heat storage control valve 25, the high-temperature steam interface 30, and the first pipe interface 28 of the first heat storage unit 100. After heat exchange, it enters the heat exchanger 11 of the second heat storage unit 100 through the second pipe interface 29 of the first heat storage unit 100 and the first pipe interface 28 of the second heat storage unit 100. This process continues through several heat storage units 100. Finally, when the high-temperature steam de-heats and becomes low-temperature condensate, it maintains essentially the original steam working pressure. To obtain the conditions for high-temperature condensation and heat release of the steam, the low-temperature water after heat exchange enters the heat storage drainage system 22 through the second pipe interface 29 and low-temperature water interface 31 of the last heat storage unit 100, and finally flows out from the heat storage drainage system 22 via the heat storage control valve 25. When the high-temperature steam passes through the heat exchanger 11, the fan 12 is in the forward rotation direction, driving air to blow towards the heat exchanger 11, and the high-temperature air generated by heat exchange in the heat exchanger 11 is then... The high-temperature air duct 13 enters the high-temperature air zone 14, and then enters the heat storage tank of the heat storage structure. The pebbles in the heat storage layer 1 flowing into the heat storage tank have gaps between them. When the high-temperature air flows through these gaps, it heats the pebbles in the heat storage layer 1, storing the heat energy in the heat storage layer 1. Several layers of equalizing air layers 2 are set inside the heat storage tank to separate the heat storage layer 1. Simultaneously, the equalizing gaps 2-2 between adjacent layers of equalizing air layers 2 are horizontally placed with a 90° projection. Thus, when the high-temperature air flows through the heat storage layer 1 and the several layers of equalizing air layers 2, the air is heated by the equalizing air layers 2. The air distribution gaps 2-2 between adjacent layers are horizontally placed with 90° projections, which can avoid the short-circuit effect caused by the straight flow of high-temperature air and can better form a uniform air distribution field, so that the high-temperature air can exchange heat with the heat storage layer 1 more evenly and store heat efficiently. The low-temperature air after heat storage and exchange finally flows into the low-temperature air zone 16 through the heat storage tank supporting ventilation structure 3-4, and then enters the fan 12 and heat exchanger 11 through the low-temperature air channel 15, where it exchanges heat with the high-temperature steam entering the heat exchanger 11 again to form high-temperature air, and the above working process is repeated.
[0035] During the heat release process, the heat storage control valve 25 is closed, the heat release control valve 26 is opened, and the heat release water pump 27 is started. The low-temperature water from the heat release water system 23 enters the heat exchanger 11 of the last heat storage unit 100 through the heat release water pump 27, the heat release control valve 26, the low-temperature water interface 31, and the second pipe interface 29 of the last heat storage unit 100. After heat exchange, it enters the heat exchanger 11 of the previous heat storage unit 100 through the first pipe interface 28 of the last heat storage unit 100 and the second pipe interface 29 of the previous heat storage unit 100. This process continues through several heat storage units 100. Finally, the high-temperature steam generated after heat exchange is delivered to the heat release steam user 24 through the first pipe interface 28 and the high-temperature steam interface 30 of the first heat storage unit 100, and finally through the heat release control valve 26. When supplying steam, the blower 12 operates in reverse, drawing the high-temperature air formed in the high-temperature air zone 14 out of the heat exchanger 11. This allows the heat energy stored in the heat storage tank to enter the heat exchanger 11 through the high-temperature air zone 14 and the high-temperature air channel 13, where it exchanges heat with the low-temperature water in the heat release water supply system 23. The low-temperature air formed after the heat exchange is then driven by the blower 12 in reverse, entering the low-temperature air zone 16 through the low-temperature air channel 15, and then flowing into the heat storage tank 3 through the heat storage tank support ventilation structure 3-4 to form a closed-loop heat release circulation channel. When flowing through the air distribution layer 2 and the heat storage layer 1 of each layer, it absorbs the heat energy stored in the heat storage layer 1, ultimately forming high-temperature air, which again enters the heat exchanger 11 through the high-temperature air zone 14 and the high-temperature air channel 13, exchanging heat with the low-temperature water in the heat release water supply system 23, thus repeating the above working process. Similarly, since several layers of air distribution layers 2 are set inside the heat storage tank 3 to separate the heat storage layer 1, and the adjacent air distribution gaps 2-2 of the air distribution layers 2 are placed horizontally with 90° projections between them, when the low-temperature air flows through the heat storage layer 1 and the several layers of air distribution layers 2, the adjacent air distribution gaps 2-2 of the air distribution layers 2 are placed horizontally with 90° projections between them, which can avoid the low-temperature air flowing in a straight line and forming a short-circuit effect. This can better form an air distribution field, so that the low-temperature air can exchange heat with the heat storage layer 1 more evenly and release heat more efficiently.
[0036] Figure 5The diagram shows a system using a novel series and parallel combination of heat storage units. Due to the different forms of heat sources, the connection forms of the heat storage units 100 for storing thermal energy in rubble are also different. For example, the energy value of storing thermal energy in the high-temperature superheated steam temperature range is basically linearly related to the temperature, so a series combination structure of heat storage units 100 can be used for energy storage. However, when storing thermal energy in the saturated steam range, the temperature value of the steam saturation point is also the phase change condensation point of the steam. At this temperature point, more than 50% of the phase change thermal energy of the superheated steam can be released. In order to fully and effectively absorb this part of the energy, multiple heat storage units 100 need to be set up in parallel at this temperature point to meet the energy storage requirements at this temperature point. Therefore, for equipment that stores superheated steam thermal energy over a wide temperature range, the heat storage units 100 need to be connected in a series and parallel combination to absorb thermal energy more effectively.
Claims
1. A thermal energy storage unit utilizing rubble to store thermal energy, characterized in that: The heat storage unit (100) consists of a heat storage tank (3) and a heat exchanger (11), a fan (12) and pipelines connected to the heat storage tank (3); The heat storage tank (3) is a barrel-shaped structure made of heat-resistant metal or heat-resistant concrete; the top of the heat storage tank (3) is connected to the high-temperature air zone (14), and the bottom of the heat storage tank (3) is connected to the low-temperature air zone (16); a heat exchanger (11) is provided in the pipeline of the high-temperature air zone (14), and the low-temperature air zone (16) is connected to the fan (12) through the pipeline; the heat storage tank (3), the high-temperature air zone (14), the fan (12) and the low-temperature air zone (16) form a closed circulating air channel with bidirectional reversible airflow; The heat storage tank (3) has a heat storage layer (1) inside. The heat storage layer (1) is divided into a bottom heat storage layer, a middle heat storage layer and a top heat storage layer from bottom to top. Each heat storage layer is made of stacked rubble. A uniform air layer (2) is provided between each heat storage layer (1), which is a uniform air channel to balance the heat storage and heat release capacity of each heat storage layer (1). The heat exchanger (11) is provided with a first pipe interface (28) and a second pipe interface (29); The above structure constitutes a heat storage unit (100).
2. The thermal energy storage unit utilizing rubble to store thermal energy according to claim 1, characterized in that: The number of the central heat storage layer (1) is between 1 and 60.
3. The thermal energy storage unit utilizing rubble to store thermal energy according to claim 1, characterized in that: The wind distribution layer (2) is constructed of strip-shaped stones (2-1), which are arranged horizontally, and wind distribution gaps (2-2) are left between each strip-shaped stone (2-1).
4. The thermal energy storage unit utilizing rubble to store thermal energy according to claim 3, characterized in that: The adjacent strips of stone (2-1) are placed horizontally with their projections intersecting at 90°.
5. The thermal energy storage unit utilizing rubble to store thermal energy according to claim 1, characterized in that: The heat storage tank (3) is provided with an insulation layer (4), which is composed of aluminum silicate cotton, perlite, and refractory insulation material castable.
6. The thermal energy storage unit utilizing rubble to store thermal energy according to claim 1, characterized in that: The fan (12) is an axial flow fan that can drive airflow in both forward and reverse directions.
7. The thermal energy storage unit utilizing rubble to store thermal energy according to claim 1, characterized in that: In each heat storage layer (1), the rubble is dry-laid without binder, and shims are set in the places where it is tightly stacked to form air channels.
8. The thermal energy storage unit utilizing rubble to store thermal energy according to claim 1, characterized in that: The heat storage tank (3) is installed in sections, with a combination structure of 1 to 2 heat storage layers (1) and air distribution layers (2) installed in the height of each section.
9. A thermal storage system comprising a thermal storage unit utilizing rubble to store thermal energy as described in claim 1, characterized in that: The system consists of several heat storage units (100) connected in series. The first pipe interface (28) on the first heat storage unit (100) is connected to the high-temperature steam heat source (21) through pipes and valves. The second pipe interface (29) on the first heat storage unit (100) is connected to the first pipe interface (28) on the second heat storage unit (100). The second pipe interface (29) on the second heat storage unit (100) is connected to the first pipe interface (28) on the next heat storage unit (100), and so on. The second pipe interface (29) on the last heat storage unit (100) is connected to the heat release water system (23) through pipes, valves and heat release water pump (27).
10. The system according to claim 9, characterized in that: In a series of heat storage units (100), one heat storage unit (100) operates at the condensation temperature of the exothermic steam and forms a parallel structure. The heat storage units (100) that operate below the condensation temperature of the steam adopt a series structure, that is: the second pipe interface (29) of the previous heat storage unit (100) is connected in parallel with the first pipe interface (28) of 2 to 20 heat storage units (100), the second pipe interface (29) of the 2 to 20 parallel heat storage units (100) is connected in series with the first pipe interface (28) of the next heat storage unit (100), and the second pipe interface (29) of the last heat storage unit (100) is connected to the exothermic water supply system (23) through pipes, valves and exothermic water pump (27).