Double-temperature-source underground energy storage device

Abstract

The invention provides a double-temperature-source underground energy storage device, which relates to the technical field of energy storage and comprises a low-temperature-source heat storage system, a high-temperature-source heat storage system and a medium transfer assembly. The low-temperature source heat storage system comprises a low-temperature heat storage tank, an organic working medium R245fa circulation loop and an organic Rankine cycle power generation component, and is adaptive to a heat source of 100-150 DEG C; the high-temperature source heat storage system comprises a high-temperature heat storage tank, a pressurized water circulation loop and a steam turbine power generation component and is matched with a heat source with the temperature larger than or equal to 200 DEG C; the two-way circulating pump realizes medium cross-system transfer; and the control and monitoring system regulates and controls the operation mode. Multi-grade heat source partitioned heat storage and graded power generation are achieved, the heat-electricity conversion efficiency is improved, multi-element heat source access is supported, and underground deployment optimizes space utilization and protection.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of energy storage, in particular to a dual-temperature-source underground energy storage device. BACKGROUND

[0002] With the increasing demand for industrial waste heat recovery and the large-scale development of renewable energy such as solar energy and geothermal energy, multi-temperature-grade heat sources have become an important part of energy systems. Among them, the medium and low temperature heat source of 100-150℃ exists widely in industrial flue gas, solar collector and low-grade geothermal heat, and the high temperature heat source above 200℃ is often found in incineration tail gas, chemical reaction heat and high-grade geothermal heat. The large number of multi-temperature-range heat sources has put forward higher requirements for energy comprehensive utilization.

[0003] However, the existing underground energy storage technology generally relies on single temperature grade heat source design, and it is difficult to realize efficient and collaborative recovery of multi-temperature-range waste heat. On the one hand, the traditional system mostly adopts a decentralized processing scheme, which not only leads to fragmented energy utilization, but also causes high equipment redundancy and increased initial investment cost; on the other hand, the heat storage medium is not optimized for different temperature ranges, and the power generation module is mostly single cycle form such as steam turbine or organic Rankine cycle, lacking of dual-temperature-source collaborative mechanism, which makes the temperature matching of heat source and power generation system poor, and the heat-electricity conversion efficiency is always at a low level.

[0004] Although dual-temperature-source energy storage can theoretically achieve precise temperature matching through staged heat storage and power generation, the existing devices are limited by insufficient performance of heat storage medium, unreasonable system coupling design and other factors, and cannot simultaneously consider high efficiency and high flexibility, so it is difficult to adapt to multi-grade mixed heat sources such as industrial waste heat and renewable energy, therefore an innovative device that can realize partitioned heat storage, precise matching of power generation cycle and adapt to underground safe deployment is needed to break through the technical bottleneck of current multi-grade energy utilization. SUMMARY

[0005] In view of the above technical deficiencies, the purpose of the present application is to provide a dual-temperature-source underground energy storage device to realize partitioned heat storage of multi-grade heat sources.

[0006] To achieve the above purpose, the technical scheme adopted by the present application is as follows: A dual-temperature-source underground energy storage device, comprising: A low-temperature-source heat storage system, comprising a low-temperature heat storage tank, a first heat exchanger and a second heat exchanger; the first loop of the first heat exchanger is connected to the low-temperature heat storage tank, and the second loop is connected to the first loop of the second heat exchanger; a first working medium pump is installed on the pipeline between the low-temperature heat storage tank and the first heat exchanger; a turbine and a second working medium pump are installed on the pipeline between the first heat exchanger and the second heat exchanger; The high-temperature source heat storage system comprises a high-temperature heat storage tank, a third heat exchanger and a fourth heat exchanger; a first loop of the third heat exchanger is connected to the high-temperature heat storage tank, and a second loop is connected to a first loop of the fourth heat exchanger; a third working medium pump is installed on a pipeline between the high-temperature heat storage tank and the third heat exchanger; a steam turbine and a fourth working medium pump are installed on a pipeline between the third heat exchanger and the fourth heat exchanger; A cold source is connected to the second heat exchanger and a second loop of the fourth heat exchanger. A bidirectional circulating pump is connected between the low-temperature heat storage tank and the high-temperature heat storage tank.

[0007] Preferably, the low-temperature heat storage tank is connected to a low-temperature waste heat source, and the high-temperature heat storage tank is connected to a high-temperature waste heat source.

[0008] Preferably, the low-temperature source heat storage system uses organic working medium R245fa as a heat transfer medium.

[0009] Preferably, the high-temperature source heat storage system uses pressurized hot water as a heat transfer medium.

[0010] Preferably, the low-temperature heat storage tank and the high-temperature heat storage tank are both filled with energy storage medium; the energy storage medium is a boronic acid-succinic acid eutectic material with a molar ratio of 6:4.

[0011] Preferably, a plurality of first liquid level sensors are arranged in the low-temperature heat storage tank; the plurality of first liquid level sensors are arranged in an equidistant array along the height direction of the low-temperature heat storage tank; and the first liquid level sensors are used to monitor the height of the liquid energy storage medium in the low-temperature heat storage tank.

[0012] Preferably, a plurality of second liquid level sensors are arranged in the high-temperature heat storage tank; and the second liquid level sensors are used to monitor the height of the liquid energy storage medium in the high-temperature heat storage tank.

[0013] Preferably, the second liquid level sensors are high-temperature resistant liquid level sensors.

[0014] Compared with the prior art, the present application has the following advantages: The present application realizes precise correspondence of "different temperature heat sources-special heat storage medium-adapted power generation cycles" through the partition design of the low-temperature source heat storage system and the high-temperature source heat storage system, which are respectively adapted to low-temperature and high-temperature heat sources; the low-temperature system adopts organic working medium R245fa circulation and matches organic Rankine cycle power generation, and the high-temperature system adopts pressurized water circulation and matches steam turbine power generation, thereby solving the problem of poor temperature matching of traditional single systems and maximizing the utilization of multi-grade heat sources.

[0015] The system adopts a boronic acid-succinic acid eutectic material with a molar ratio of 6:4 as an energy storage medium, which can realize latent heat storage through solid-liquid phase change in a low temperature range, and can also combine sensible heat and thermochemical heat storage to form a three-mode heat storage in a high temperature range, compared with traditional phase change materials, the energy storage density is greatly improved, which provides support for efficient heat storage and stable heat release.

[0016] The reversible transfer of the heat storage medium between the low temperature tank and the high temperature tank is realized through a bidirectional circulating pump, the medium in the low temperature tank can be dispatched according to the power generation demand of the high temperature source in the heat storage stage, the high temperature source heat storage system can be preferentially called to meet the peak power generation demand in the heat release stage, the low temperature source heat storage system can supplement the basic load or standby power, and meanwhile, various heat sources such as industrial waste heat, solar energy and geothermal energy can be supported to access, so that the problem of insufficient adaptability of the traditional system is solved.

[0017] The low temperature heat storage tank and the high temperature heat storage tank are both designed to be buried underground at a depth of 5-10m, are externally coated with an aerogel insulation layer and a polyurethane moisture-proof layer, and the pipelines are made of seamless stainless steel, so that the ground space occupation is reduced, the heat loss is controlled, the underground humid environment is adapted, and the facility protection and concealment are improved. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 It is a structural schematic view of the present application.

[0019] Among them: 1, low temperature waste heat source; 2, low temperature heat storage tank; 3, first liquid level sensor; 4, first working medium pump; 5, first heat exchanger; 6, second working medium pump; 7, turbine; 8, second heat exchanger; 9, cold source; 10, bidirectional circulating pump; 11, high temperature waste heat source; 12, second liquid level sensor; 13, high temperature heat storage tank; 14, third working medium pump; 15, third heat exchanger; 16, fourth working medium pump; 17, steam turbine; 18, fourth heat exchanger. DETAILED DESCRIPTION

[0020] The present application will be further described below with reference to the accompanying drawings.

[0021] As Figure 1 shown, a dual-temperature-source underground energy storage device includes a low-temperature-source heat storage system and a high-temperature-source heat storage system; heat transfer medium is used in the low-temperature-source heat storage system and the high-temperature-source heat storage system to conduct heat transfer; The low-temperature-source heat storage system (100-150 oC) comprising a low-temperature heat storage tank 2, a first working medium pump 4, a first heat exchanger 5, a turbine 7, a second heat exchanger 8, a second working medium pump 6; the low-temperature heat storage tank 2 is connected to the low-temperature waste heat source 1; the first heat exchanger 5 is connected to the low-temperature heat storage tank 2 in the first loop and connected to the first loop of the second heat exchanger 8 in the second loop; the first working medium pump 4 is connected to the pipeline between the low-temperature heat storage tank 2 and the first heat exchanger 5; the first working medium pump 4 is used to pump the heat transfer medium between the low-temperature heat storage tank 2 and the first heat exchanger 5, so that the heat in the low-temperature heat storage tank 2 is transferred to the first heat exchanger 5; the turbine 7 and the second working medium pump 6 are connected to the pipeline between the first heat exchanger 5 and the second heat exchanger 8; the second working medium pump 6 is used to pump the heat transfer medium between the first heat exchanger 5 and the second heat exchanger 8, so that the heat in the first heat exchanger 5 is transferred to the turbine 7; High-temperature source heat storage system (200 o C) comprising a low-temperature heat storage tank 2, a first working medium pump 4, a first heat exchanger 5, a turbine 7, a second heat exchanger 8, a second working medium pump 6; the low-temperature heat storage tank 2 is connected to the low-temperature waste heat source 1; the first heat exchanger 5 is connected to the low-temperature heat storage tank 2 in the first loop and connected to the first loop of the second heat exchanger 8 in the second loop; the first working medium pump 4 is connected to the pipeline between the low-temperature heat storage tank 2 and the first heat exchanger 5; the first working medium pump 4 is used to pump the heat transfer medium between the low-temperature heat storage tank 2 and the first heat exchanger 5, so that the heat in the low-temperature heat storage tank 2 is transferred to the first heat exchanger 5; the turbine 7 and the second working medium pump 6 are connected to the pipeline between the first heat exchanger 5 and the second heat exchanger 8; the second working medium pump 6 is used to pump the heat transfer medium between the first heat exchanger 5 and the second heat exchanger 8, so that the heat in the first heat exchanger 5 is transferred to the turbine 7; The low-temperature heat storage tank 2 and the high-temperature heat storage tank 13 are both filled with energy storage medium; the second loop of the second heat exchanger 8 and the fourth heat exchanger 18 are both connected to the cold source 9; the cold source 9 is used to cool the heat transfer medium in the second heat exchanger 8 and the fourth heat exchanger 18; the low-temperature heat storage tank 2 and the high-temperature heat storage tank 13 are connected to the bidirectional circulating pump 10.

[0022] Further, the low-temperature source heat storage system uses organic working medium R245fa as the heat transfer medium.

[0023] Further, the high-temperature source heat storage system uses pressurized hot water as the heat transfer medium.

[0024] Further, the energy storage medium is a boronic acid-succinic acid eutectic material with a molar ratio of 6:4; it has a latent heat storage capacity of 100-150 o C solid-liquid phase change (latent heat storage); 200 oC Based on its three-mode characteristics of sensible heat, latent heat and thermo-chemical heat storage, the total heat storage density is as high as 394 J / g by adjusting the molecular structure to realize sensible heat, latent heat and thermo-chemical heat storage.

[0025] The bidirectional circulating pump 10 is used to transport the liquid boric acid-succinic acid eutectic material in the low-temperature heat storage tank 2 to the high-temperature heat storage tank 13, so as to realize the reversible transfer of the heat storage medium to the high-temperature source heat storage system.

[0026] Further, a plurality of first liquid level sensors 3 are arranged in the low-temperature heat storage tank 2, and the plurality of first liquid level sensors 3 are arranged in an equidistant array along the height direction of the low-temperature heat storage tank 2; the first liquid level sensor 3 is used to monitor the height of the liquid energy storage medium in the low-temperature heat storage tank 2.

[0027] Further, a plurality of second liquid level sensors 12 are arranged in the high-temperature heat storage tank 13; the second liquid level sensor 12 is used to monitor the height of the liquid energy storage medium in the high-temperature heat storage tank 13.

[0028] Further, the second liquid level sensor 12 is a high-temperature resistant liquid level sensor.

[0029] Operation method: (1) Low-temperature heat storage The low-temperature waste heat source 1 (such as 100-150℃ industrial waste gas, waste water, etc.) exchanges heat with the organic working medium R245fa through a conventional heat exchanger, so that the R245fa is heated and partially vaporized.

[0030] The vaporized R245fa transfers heat to the boric acid-succinic acid eutectic phase change material in the low-temperature heat storage tank 2. The material changes from solid to liquid during the heat absorption process, effectively absorbing waste heat through the latent heat of solid-liquid phase change, and realizing long-time storage of low-grade heat energy.

[0031] The first liquid level sensor 3 of different heights is arranged in the low-temperature heat storage tank 2, which is used to monitor the phase change process in real time. When the liquid level height no longer rises, it indicates that the eutectic material has completed the solid-liquid transition, and the heat storage process is completed. By reasonably controlling the circulation flow and the heat exchange area, the phase change material can be fully heated and smoothly complete the melting heat storage.

[0032] (2) Low-temperature power generation (organic Rankine cycle) When the energy needs to be released, the first working medium pump 4 drives the R245fa in the first circuit of the first heat exchanger 5 to circulate between the low-temperature heat storage tank 2 and the first heat exchanger 5. At this time, the boric acid-succinic acid eutectic material in the low-temperature heat storage tank 2 gradually solidifies, releases latent heat and transfers heat to the first heat exchanger 5. Then, the second circuit of the first heat exchanger 5 uses the heat to heat the R245fa organic working medium, so that it evaporates into high-pressure steam and enters the turbine 7 to expand and do work, driving the generator to generate electricity.

[0033] The expanded R245fa working fluid is cooled and condensed by the second heat exchanger 8 and returned to the first heat exchanger 5 by the second working fluid pump 6, forming a closed cycle, thereby realizing energy release of the low-temperature heat storage system and low-temperature waste heat power generation.

[0034] (3) High-temperature heat storage A bidirectional circulation pump 10 transports the melted liquid energy storage medium (boric acid-succinic acid eutectic phase change material) in the low-temperature heat storage tank 2 to the high-temperature heat storage tank 13. High-temperature waste heat source 11 (such as 300-500°C flue gas or kiln exhaust) heats pressurized water through a heat exchanger, raising its temperature to above 200°C and forming saturated or superheated steam. The pressurized steam then acts as a heat transfer medium, transferring heat to the high-temperature heat storage tank 13.

[0035] Inside the high-temperature heat storage tank 13, the boric acid-succinic acid eutectic phase change material not only stores heat through sensible and latent heat but also undergoes a reversible thermochemical reaction within the temperature range of 160-200°C. This involves the endothermic decomposition of boric acid into metaboric acid and water. During the exothermic reaction, this reaction reverses, with the metaboric acid and water reacting to regenerate boric acid, releasing chemical reaction heat. This enables the boric acid-succinic acid eutectic phase change material to achieve the synergistic storage of sensible, latent, and thermochemical energy, making it a "trimodal" energy storage material.

[0036] Therefore, by utilizing the "trimodal" characteristics of this material, the boric acid-succinic acid eutectic material in the high-temperature heat storage tank 13 can be further heated to ≥200°C, effectively achieving high-density storage of high-grade thermal energy and providing a stable heat source for subsequent high-temperature power generation.

[0037] (4) High-temperature power generation (steam-turbine power generation) When power is needed, the third working fluid pump 14 starts, driving the pressurized water in the first circuit of the third heat exchanger 15 to circulate between the high-temperature heat storage tank 13 and the third heat exchanger 15. During the circulation process, the pressurized water absorbs the heat released by the boric acid-succinic acid eutectic material in the high-temperature heat storage tank 13 and transfers it to the second circuit of the third heat exchanger 15.

[0038] During this process, the heat storage medium gradually solidifies from a liquid state, releasing latent heat. Simultaneously, the metaboric acid reacts with water to regenerate boric acid, further releasing heat from the chemical reaction. This heat is transferred to the second circuit of the third heat exchanger 15, heating the pressurized water there and evaporating it into high-temperature, high-pressure steam.

[0039] The high-pressure pressurized water vapor is delivered to the steam turbine 17 through the fourth working medium pump 16 to expand and do work, driving the steam turbine to drive the generator to output electric energy. The expanded steam enters the fourth heat exchanger 18 and is cooled into pressurized water, and then returns to the third heat exchanger 15, forming a closed water-steam circulation system. Through the circulation process, the high-temperature heat storage unit can stably release stored energy and efficiently realize the conversion of energy to power generation.

[0040] (5) Cooperative operation When the system operates in the grid peak-valley regulation mode, the high-temperature source heat storage system is preferentially used to provide peak power output to meet the demand of the grid load peak. The low-temperature source heat storage system is used to provide basic load power to ensure the continuity and stability of power output; when the load fluctuates, the low-temperature system can also be used as backup power to supplement the high-temperature system to avoid interruption of grid power supply. By controlling the system to coordinate the operation of the double systems, the low-temperature waste heat can be fully utilized, and the efficient utilization of high-temperature waste heat can be ensured, realizing stable output and flexible scheduling of power.

[0041] Implementation method: Low-temperature heat storage-power generation process: S1, the heat of the low-temperature waste heat source 1 (industrial low-temperature waste heat, solar heat collection) is transferred to the low-temperature heat storage tank 2 through the organic working medium R245fa; S2, the boric acid-succinic acid eutectic material in the low-temperature heat storage tank 2 absorbs heat and undergoes solid-liquid phase change, completing the heat storage in the temperature range of 100~150 o C; S3, the liquid level sensor monitors the liquid medium height in the low-temperature heat storage tank 2 in real time to determine the heat storage progress.

[0042] S4, the first working medium pump 4 drives the organic working medium R245fa to circulate between the low-temperature heat storage tank 2 and the first heat exchanger 5, transferring heat to the first heat exchanger 5; S5, the low-boiling-point working medium absorbs heat in the first heat exchanger 5 and then enters the turbine 7 to do work and generate power; S6, the working medium after doing work is cooled by the cold source 9 through the second heat exchanger 8, and then is sent back to the first heat exchanger 5 through the second working medium pump 6, completing the organic Rankine cycle.

[0043] High-temperature heat storage-power generation process: S1, the bidirectional circulation pump 10 delivers the liquefied boric acid-succinic acid eutectic material in the low-temperature heat storage tank 2 to the high-temperature heat storage tank 13; S2, the heat of the high-temperature waste heat source 11 (industrial medium-high temperature waste heat, geothermal heat) is transferred to the high-temperature heat storage tank 13 through pressurized water; S3, the eutectic material in the high-temperature heat storage tank 13 further absorbs heat using the three-mode heat storage characteristics, and the temperature rises to above 200 o C, completing high-temperature heat storage; S4, the third working medium pump 14 drives the pressurized water to circulate between the high-temperature heat storage tank 13 and the third heat exchanger 15 to transfer high-temperature heat; S5, the pressurized water enters the steam turbine 17 to do work and generate electricity after absorbing heat in the third heat exchanger 15; S6, the water after doing work is cooled by the fourth heat exchanger 18 and is sent back to the third heat exchanger 15 by the fourth working medium pump 16, completing the steam turbine 17 cycle.

[0044] Key equipment parameters: Low-temperature heat storage tank 2: diameter 2 m, height 4 m, pressure resistance ≥0.6 MPa, 1 set of first liquid level sensor 3 is arranged every 0.8 m along the height in the tank to monitor the height of liquid medium; High-temperature heat storage tank 13: diameter 2.5 m, height 5 m, pressure resistance ≥2.5 MPa, second liquid level sensor 12 is used in the tank to monitor the medium state; Organic Rankine turbine 7: adapted to R245fa working medium, rated power 500 kW, inlet temperature 150 o C; Steam turbine 17: adapted to pressurized water, rated power 1500 kW, inlet temperature 250 o C; Bidirectional circulating pump 10: adjustable flow (5~10 m 3 / h), high temperature resistance ≥180 o C, realizing bidirectional delivery of medium.

[0045] Control logic: Heat storage stage: when high-temperature waste heat needs to be generated and the proportion of liquid medium in the low-temperature heat storage tank 2 reaches 95%, the bidirectional circulating pump 10 is started to deliver the medium to the high-temperature heat storage tank 13; Heat release stage: according to the power generation demand, the low-temperature system and the high-temperature system can be independently operated or cooperatively operated (preferably, the high-temperature system is called to meet the high-power demand, and the low-temperature system supplements the base load); Underground deployment of steam The low-temperature heat storage tank 2 and the high-temperature heat storage tank 13 are buried underground (depth 5~10 m), externally coated with 5 cm thick aerogel insulation layer + 8 cm thick polyurethane moisture-proof layer, and the heat loss is controlled at ≤3% per month; The system pipeline is made of seamless stainless steel material, the low-temperature pipeline can resist 150 o C / 0.6 MPa, the high-temperature pipeline can resist 300 o C / 3 MPa, and is suitable for underground humid environment.

Claims

1. A dual-temperature source underground energy storage device, characterized in that: include: The low-temperature source heat storage system includes a low-temperature heat storage tank, a first heat exchanger, and a second heat exchanger; the first circuit of the first heat exchanger is connected to the low-temperature heat storage tank, and the second circuit is connected to the first circuit of the second heat exchanger; a first working fluid pump is installed on the pipeline between the low-temperature heat storage tank and the first heat exchanger; a turbine and a second working fluid pump are installed on the pipeline between the first heat exchanger and the second heat exchanger; The high-temperature source heat storage system includes a high-temperature heat storage tank, a third heat exchanger, and a fourth heat exchanger; the first circuit of the third heat exchanger is connected to the high-temperature heat storage tank, and the second circuit is connected to the first circuit of the fourth heat exchanger; a third working fluid pump is installed on the pipeline between the high-temperature heat storage tank and the third heat exchanger; a steam turbine and a fourth working fluid pump are installed on the pipeline between the third heat exchanger and the fourth heat exchanger; a cold source connected to the second circuit of the second heat exchanger and the fourth heat exchanger; A bidirectional circulation pump is connected between the low-temperature heat storage tank and the high-temperature heat storage tank.

2. A dual-temperature source underground energy storage device according to claim 1, characterized in that: The low-temperature heat storage tank is connected to the low-temperature waste heat source; the high-temperature heat storage tank is connected to the high-temperature waste heat source.

3. The dual-temperature source underground energy storage device according to claim 1, characterized in that: The low-temperature source heat storage system uses the organic working fluid R245fa as the heat transfer medium.

4. A dual-temperature source underground energy storage device according to claim 1, characterized in that: The high-temperature source heat storage system uses pressurized hot water as a heat transfer medium.

5. A dual-temperature source underground energy storage device according to any one of claims 1 to 4, characterized in that: The low-temperature heat storage tank and the high-temperature heat storage tank are both filled with energy storage medium; the energy storage medium is boric acid-succinic acid eutectic material with a molar ratio of 6:

4.

6. A dual-temperature source underground energy storage device according to claim 5, characterized in that: A plurality of first liquid level sensors are provided in the low-temperature heat storage tank, and the plurality of first liquid level sensors are arranged in an array at equal intervals along the height direction of the low-temperature heat storage tank; the first liquid level sensors are used to monitor the height of the liquid energy storage medium in the low-temperature heat storage tank.

7. The dual-temperature source underground energy storage device according to claim 5, characterized in that: A plurality of second liquid level sensors are provided in the high-temperature heat storage tank; the second liquid level sensors are used to monitor the height of the liquid energy storage medium in the high-temperature heat storage tank.

8. A dual-temperature source underground energy storage device according to claim 7, characterized in that: The second liquid level sensor is a high temperature resistant liquid level sensor.

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