A compressed gas energy storage system with sediment heat storage

Abstract

This application relates to the field of compressed air energy storage and discloses a compressed gas energy storage system using sediment thermal storage. The system includes: an underground cavity for storing compressed gas; a porous sediment mass accumulated at the bottom of the underground cavity; and an injection / production tubing string, with its head connected to a compressed gas source and its tail inserted into the sediment mass within the underground cavity. This application, by adding sediment mass to the underground cavity and combining it with the injection / production tubing string inserted into the sediment mass, allows the underground cavity to store the potential energy of the compressed gas while simultaneously storing its thermal energy through the sediment mass. Furthermore, it utilizes the thermal storage capacity of the surrounding soil and rock mass to reduce heat loss within the underground cavity. This achieves the simultaneous storage of both the potential and thermal energy of the gas within the underground cavity, reducing or eliminating the need for surface thermal storage devices. This solves the problems of large footprint and high construction costs associated with compressed air energy storage systems, thereby increasing energy storage capacity, reducing land occupation, and lowering construction costs.

Description

Technical Field

[0001] This application belongs to the field of compressed air energy storage, specifically relating to a compressed gas energy storage system for sludge thermal storage. Background Technology

[0002] Compressed air energy storage (CAES) is a technology that uses compressed air to store energy. It boasts advantages such as long operating cycles, large storage capacity, and low construction costs. Currently, CAES is considered the second most suitable technology for large-scale power storage at the GW level, after pumped hydro storage. Its working principle is as follows: during off-peak hours, electrical energy is used to compress air to high pressure and store it in a cavity or pressure vessel, converting electrical energy into the internal energy of the air for storage. During peak hours, the high-pressure air is released from the storage chamber and enters the combustion chamber, where it is burned with fuel to heat up and drive a turbine to generate electricity. CAES can help smooth peak and valley loads on the power grid, improving the temporal and spatial unevenness of power generation.

[0003] As described above, a significant portion of the energy in a compressed air energy storage system is converted into heat during air compression, which is not effectively utilized. This is a major reason for the overall low efficiency of the system. To improve the efficiency of a compressed air energy storage system, a heat storage device can be added to store the heat generated during air compression. This heat can then be used to preheat the compressed air during power generation, thus achieving heat recovery. A compressed air energy storage system with an added heat storage device is also called an adiabatic compressed air energy storage system.

[0004] In existing technologies, compressed air energy storage systems typically use ground-based thermal storage devices, employing materials such as water, heat transfer oil, and molten salt. The problem with water as a thermal storage medium is that, limited by its boiling point, its storage temperature remains below 200°C even under pressure, resulting in bulky storage containers. Heat transfer oil generally has a lifespan of 10 years, is subject to aging, and poses risks of leakage and environmental pollution, as well as waste oil disposal issues. Molten salt thermal storage devices have high piping costs and are expensive. In summary, compressed air energy storage systems generally suffer from large footprints and high construction costs. Summary of the Invention

[0005] The purpose of this application is to provide a compressed gas energy storage system for sludge thermal storage, which solves the problems of large footprint and high construction cost of compressed air energy storage system thermal storage devices, thereby achieving the effects of increasing energy storage density, reducing ground land occupation, and reducing construction costs.

[0006] To achieve the above objectives, this application provides a compressed gas energy storage system for sludge thermal storage, comprising:

[0007] An underground cavity used to store compressed gas;

[0008] The sediment, which is porous, accumulates at the bottom of the underground cavity;

[0009] The injection and production tubing has a head end for connecting to a compressed gas source and an end end inserted into the sediment body within the underground cavity.

[0010] In some embodiments, the underground cavity is a salt cavern, and the sediment is salt cavern sediment or solid heat storage particles.

[0011] In some embodiments, the volume of the sediment accumulated in the underground cavity accounts for 60%-80% of the volume of the underground cavity.

[0012] In some embodiments, the injection / production tubing is inserted into the sediment to a depth of 60%-80% of the height to which the sediment accumulates in the underground cavity.

[0013] In some embodiments, the injection-production tubing is provided with a tubing head inserted into the sediment body at its end, and the sidewall of the tubing head is provided with a plurality of pores evenly distributed in a ring.

[0014] In some embodiments, the diameter of the pores is 20-100 mm, and the spacing between the pores is 2-4 times the diameter; or the length of the vertically distributed pores accounts for 20%-60% of the depth of the injection-production tubing inserted into the sediment body.

[0015] In some embodiments, multiple injection and production tubing strings are arranged in parallel at intervals, the heads of the multiple injection and production tubing strings are merged and connected to the compressed gas source, and the ends of the multiple injection and production tubing strings are respectively inserted into the sediment body in different areas of the underground cavity.

[0016] In some embodiments, the compressed gas is one of air, carbon dioxide, nitrogen, oxygen, hydrogen, and ammonia.

[0017] In some embodiments, the compressed gas energy storage system further includes a heating resistance wire disposed within the underground cavity, the heating resistance wire being used to heat the compressed gas within the underground cavity.

[0018] In some embodiments, the compressed gas energy storage system further includes a heat extraction component, the heat extraction component comprising:

[0019] Gas heat exchange tubes are used to connect the underground cavity;

[0020] Liquid heat exchange tubes are used to connect to external heating pipes.

[0021] A heat exchanger is used for heat exchange between the gas heat exchange tube and the liquid heat exchange tube.

[0022] Compared with the prior art, the beneficial effects of this application are as follows:

[0023] This application, by adding sediment to an underground cavity and inserting injection and production tubing into the sediment, enables the underground cavity to store the potential energy of compressed gas while simultaneously storing the thermal energy of the compressed gas through the sediment. Furthermore, it utilizes the thermal storage capacity of the surrounding soil and rock to reduce heat loss within the underground cavity. This allows for the simultaneous storage of both the potential and thermal energy of the gas within the underground cavity, reducing or eliminating the need for surface thermal storage devices. This addresses the issues of large land area and high construction costs associated with compressed air energy storage systems, achieving the goals of increasing energy storage capacity, reducing land occupation, and lowering construction costs.

[0024] Other features and advantages of the embodiments of this application will be described in detail in the following detailed description section. Attached Figure Description

[0025] The accompanying drawings are provided to further illustrate the embodiments of this application and form part of the specification. They are used together with the following detailed description to explain the embodiments of this application, but do not constitute a limitation on the embodiments of this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without any inventive effort. In the drawings:

[0026] Figure 1 This is a structural diagram of a compressed gas energy storage system according to a specific embodiment of this application.

[0027] Figure 2 This is a schematic diagram of the airflow during the energy storage stage of the compressed gas energy storage system according to a specific embodiment of this application.

[0028] Figure 3 This is a schematic diagram of the airflow during the energy release phase of the compressed gas energy storage system according to a specific embodiment of this application.

[0029] Figure 4 This is a schematic diagram of the airflow in the energy storage stage of the tube head, which is a specific embodiment of this application.

[0030] Explanation of reference numerals in the attached drawings: 1. Underground cavity; 2. Sediment body; 3. Injection and production tubing; 31. Tubing head; 32. Vent; 4. Heating resistance wire; 51. Heat extraction assembly; 52. Gas heat exchanger tube; 53. Liquid heat exchanger tube. Detailed Implementation

[0031] The specific embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this application.

[0032] like Figures 1 to 4 As shown, a compressed gas energy storage system for sludge thermal storage specifically includes:

[0033] Underground cavity 1, used for storing compressed gas;

[0034] Sediment 2, which is porous, accumulates at the bottom of underground cavity 1;

[0035] The injection and production tubing 3 has a head end for connecting to a compressed gas source and an end end inserted into the sediment 2 in the underground cavity 1.

[0036] In this application, the underground cavity 1 serves as a container for storing compressed gas and can withstand a certain pressure from the compressed gas. The sediment 2 has a certain accumulation height and is used to store heat. The injection-production tubing 3 is used to input and output compressed gas into the underground cavity 1. During the energy storage stage, the high-temperature and high-pressure gas output from the compressed gas source enters the underground cavity 1 through the end of the injection-production tubing 3. The gas flows upward through the sediment 2, and at the same time, it gradually heats the sediment 2 from bottom to top. The cooled gas accumulates in the upper cavity of the underground cavity 1. After the gas pressure in the underground cavity 1 reaches the preset range, the compressed gas source stops outputting, and the potential energy and thermal energy of the gas are stored in the underground cavity 1. During the energy release stage, the gas in the upper part of the underground cavity 1 flows downward through the sediment 2, and at the same time, it is gradually heated by the sediment 2 from top to bottom. The heated gas enters the end of the injection-production tubing 3, and the high-temperature and high-pressure gas is output downstream through the head end of the injection-production tubing 3.

[0037] In this application, the porous nature of the sediment body 2 and the design of the injection / production tubing 3 inserted into the sediment body 2 allow for sufficient heat exchange between the compressed gas and the sediment body 2 as the gas passes through, achieving cooling or heating of the compressed gas, i.e., heat energy transfer. Furthermore, because the compressed gas is cooled before being stored in the upper cavity of the underground cavity 1, a larger volume of compressed gas can be stored under the same gas pressure. Moreover, compared to surface-mounted heat storage devices, the surrounding soil and rock of the underground cavity 1 have poor heat transfer capacity. After energy storage and heating, the underground cavity 1 forms a stable temperature field with a small gradient with the soil and rock, resulting in slow heat loss within the underground cavity 1 and high heat storage efficiency, thereby improving the overall energy efficiency of the system. Finally, since the potential energy and thermal energy of compressed gas are stored simultaneously in the underground cavity 1, the need for a separate thermal storage device can be eliminated, thereby reducing the process and complexity of the compressed gas energy storage system. This can further improve the overall energy efficiency of the system and enable the compressed gas energy storage system to adapt to high-cycle cyclic loads, thus improving economic benefits.

[0038] This application adds a sediment body 2 inside the underground cavity 1, so that the underground cavity 1 can store the potential energy of compressed gas and the thermal energy of compressed gas through the sediment body 2. By utilizing the heat storage capacity of the surrounding rock and soil, the heat loss of the underground cavity 1 is reduced. This allows for the simultaneous storage of the potential energy and thermal energy of the gas inside the underground cavity 1, which can reduce or eliminate the need for surface heat storage devices. This solves the problems of large footprint and high construction cost of heat storage devices in compressed air energy storage systems, thereby increasing energy storage capacity, reducing surface land occupation, and lowering construction costs.

[0039] Specifically, underground cavity 1 is a salt cavern, and sediment body 2 is salt cavern sediment or solid heat storage particles.

[0040] Due to my country's unique lacustrine sedimentary history, its salt resources are primarily layered salt rock structures, characterized by the interweaving of rock and salt layers. Consequently, Chinese salt caverns typically contain large amounts of sediment, which is the debris deposit formed after the collapse and breakage of rock layers following brine extraction. Traditional research suggests that this sediment occupies the gas storage space of the salt cavern, reducing its gas storage capacity and making it unsuitable as the underground cavity 1 for compressed gas energy storage systems. However, what is often overlooked is that salt cavern sediment, as a geotechnical material, is a naturally excellent sensible heat storage material. The main components of salt cavern sediment are mudstone and gypsum, with melting points above 1200℃, possessing a considerable heat capacity. This application utilizes idle large salt caverns as the underground cavity 1 and a large amount of salt cavern sediment as the sediment body 2, achieving simultaneous storage of gas potential and thermal energy within the underground cavity 1. This approach offers advantages such as small construction workload, large gas storage capacity, and large heat storage capacity, further reducing the construction cost of compressed gas energy storage systems.

[0041] In some embodiments, if the amount of salt sludge accumulated in the selected salt cavern is insufficient, solid heat storage particles can be added to the salt cavern to increase the amount of sludge 2. The solid heat storage particles are particulate matter made of sensible heat storage material.

[0042] Those skilled in the art will understand that the underground cavity 1 in this application is not limited to the aforementioned salt cavern, but can also be a coal seam cavern or an artificial chamber, etc. Any underground cavity 1 capable of storing high-temperature and high-pressure gas should fall within the protection scope of this application. Correspondingly, the sediment 2 is solid heat storage particles.

[0043] Specifically, the volume of sediment 2 accumulated in the underground cavity 1 accounts for 60%-80% of the volume of the underground cavity 1. If the sediment 2 accounts for too small a proportion, its cooling effect on the compressed gas will be poor, resulting in excessively high temperatures of the compressed gas stored in the underground cavity 1. Under constant gas pressure, the volume of stored compressed gas will decrease. If the sediment 2 accounts for too large a proportion, it will directly reduce the space in the underground cavity 1 used for storing compressed gas, thus reducing the volume of stored compressed gas. Only within a suitable range of sediment 2 proportions can the underground cavity 1 meet the requirements of simultaneously storing the potential energy and thermal energy of the compressed gas, thereby obtaining a better combination of gas storage capacity and heat storage capacity.

[0044] Specifically, the injection-production tubing 3 is inserted into the sediment body 2 to a depth of 60%-80% of the height of the sediment body 2 accumulated in the underground cavity 1. If the insertion depth of the injection-production tubing 3 is too deep, the flow resistance of the compressed gas in the sediment body 2 will be greater, thereby reducing the working flow rate of the compressed gas; if the insertion depth of the injection-production tubing 3 is too shallow, the heat exchange between the compressed gas and the sediment body 2 will be insufficient, resulting in poor cooling effect of the compressed gas during the energy storage stage and poor heating effect during the energy release stage. Only an insertion depth within the appropriate range can enable the compressed gas to conduct rapid and sufficient heat exchange with the sediment body 2, thereby improving the energy storage capacity and energy storage speed of the compressed gas energy storage system.

[0045] In some embodiments, the injection-production tubing 3 extends vertically from the ground into the underground cavity 1. During the energy storage phase, a compressor on the ground inputs high-temperature, high-pressure gas from the head end of the injection-production tubing 3, storing it within the underground cavity 1. During the energy release phase, the high-temperature, high-pressure gas from the underground cavity 1 is output from the head end of the injection-production tubing 3, driving a turbine unit to generate electricity. The operating temperature of the underground cavity 1 is 100-400℃. The compressed gas charging and discharging cycle is one day, allowing the heat stored in the sediment 2 within the underground cavity 1 to be released and utilized in a short time, thereby reducing heat loss from the sediment 2 and improving the overall energy efficiency of the compressed gas energy storage system.

[0046] like Figure 4 As shown, specifically, the injection / production tubing 3 has a tubing head 31 inserted into the sediment body 2 at its end. Multiple vents 32 are evenly distributed in a ring on the side wall of the tubing head 31. The vents 32 increase the flow channels for compressed gas, increasing the gas flow capacity within the sediment body 2. This allows compressed gas to flow in and out simultaneously from both the end face and side face of the tubing head 31, increasing the contact area between the compressed gas and the sediment body 2, and improving the heat exchange rate between them. This, in turn, increases the heat storage rate and capacity of the sediment body 2.

[0047] In some embodiments, the injection / production tubing 3 is composed of multiple tubing segments connected vertically in sequence, with the tubing head 31 connected to the last tubing segment. The tubing head 31 and its vent holes 32 are all inserted into the sediment body 2.

[0048] Furthermore, the pore diameter of the pores 32 is 20-100mm, and the spacing between the pores 32 is 2-4 times the pore diameter. If the diameter of the tube head 31 is large, then a correspondingly larger pore diameter for the pores 32 should be selected. The pore diameter of the pores 32 is related to the diameter of the tube head 31; a suitable pore diameter range ensures that most of the compressed gas flows in and out from the bottom end face of the tube head 31, while a small amount of compressed gas flows in and out from the side of the tube head 31. This allows the compressed gas to form a three-dimensional heat exchange with the sediment 2, further improving the heat storage rate and heat storage capacity of the sediment 2.

[0049] Furthermore, the vertically distributed length of the vents 32 accounts for 20%-60% of the depth to which the injection / production tubing 3 is inserted into the sediment body 2. The vents 32 are distributed from bottom to top on the bottom side wall of the tubing head 31. Limiting the length of the vent distribution ensures that the compressed gas flowing out and in from the side of the tubing head 31 can still have sufficient heat exchange with the sediment body 2 above it, guaranteeing the cooling effect of the compressed gas during the energy storage stage and the heating effect during the energy release stage, further improving the heat storage capacity of the sediment body 2.

[0050] Optionally, multiple injection and production tubing strings 3 are arranged in parallel at intervals. The heads of the multiple injection and production tubing strings 3 merge and are connected to a compressed gas source. The ends of the multiple injection and production tubing strings 3 are respectively inserted into the sediment bodies 2 in different areas of the underground cavity 1. Compressed gas flows out and in from the ends of the multiple injection and production tubing strings 3, and at the same time exchanges heat with the sediment bodies 2 in different areas. This avoids local heat accumulation or loss in the sediment bodies 2, reduces the heat conduction process between the sediment bodies 2, and allows the compressed gas to cool down or heat up more quickly, thereby improving the energy storage capacity and energy storage speed of the compressed gas energy storage system.

[0051] Specifically, the compressed gas is one of the following: air, carbon dioxide, nitrogen, oxygen, hydrogen, and ammonia.

[0052] Optionally, the compressed gas energy storage system also includes a heating resistance wire 4 installed in the underground cavity 1. The heating resistance wire 4 is used to heat the compressed gas in the underground cavity 1. After the heat in the underground cavity 1 is lost for a long time, the compressed gas cannot be heated to the preset working temperature by the sediment body 2. At this time, the heating resistance wire 4 works to provide additional heating to the compressed gas in the underground cavity 1 so as to output the required high temperature and high pressure gas downstream.

[0053] In some embodiments, the heating resistance wire 4 is disposed above the sediment body 2, and the heating resistance wire 4 can be powered by a ground-based wind turbine or photovoltaic generator.

[0054] Optionally, the compressed gas energy storage system also includes a heat extraction component, specifically including:

[0055] Gas heat exchange tube 51, used to connect to underground cavity 1;

[0056] Liquid heat exchange tube 52 is used to connect to external heating pipes;

[0057] Heat exchanger 53 is used for heat exchange between gas heat exchange tube 51 and liquid heat exchange tube 52.

[0058] In this application, under certain operating conditions, the underground cavity 1 stores energy but releases it only after a long period of time; the heat inside the underground cavity 1 is gradually and naturally lost over time; the addition of heat extraction components can maximize the utilization of the heat stored in the underground cavity 1. The liquid heat exchange pipe 52 of the heat extraction components is connected to the external heating pipe, and the compressed gas energy storage system can function as a heat storage tank.

[0059] In some embodiments, the gas heat exchange tube 51 is connected to the upper cavity of the underground cavity 1. High-pressure compressed gas flows through the gas heat exchange tube 51 to the heat exchanger 53 for gas-liquid heat exchange, heating the liquid in the liquid heat exchange tube 52 to achieve external heat supply.

[0060] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0061] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between components; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0062] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0063] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A compressed gas energy storage system for sludge thermal storage, characterized in that, The compressed gas energy storage system includes: An underground cavity (1) is used to store compressed gas; The sediment (2) has porous characteristics and accumulates at the bottom of the underground cavity (1); The injection and extraction tubing (3) has a head end for connecting to a compressed gas source and an end end inserted into the sediment body (2) in the underground cavity (1).

2. The compressed gas energy storage system for sludge thermal storage according to claim 1, characterized in that, The underground cavity (1) is a salt cavern, and the sediment (2) is salt cavern sediment or solid heat storage particles.

3. The compressed gas energy storage system for sludge thermal storage according to claim 2, characterized in that, The volume of the sediment (2) accumulated in the underground cavity (1) accounts for 60%-80% of the volume of the underground cavity (1).

4. The compressed gas energy storage system for sludge thermal storage according to claim 2, characterized in that, The injection-production tubing (3) is inserted into the sediment (2) to a depth of 60%-80% of the height of the sediment (2) accumulated in the underground cavity (1).

5. The compressed gas energy storage system for sludge thermal storage according to claim 1, characterized in that, The injection and production tubing (3) has a tubing head (31) at its end that is inserted into the sediment body (2), and a plurality of pores (32) are evenly distributed in a ring on the side wall of the tubing head (31).

6. The compressed gas energy storage system for sludge thermal storage according to claim 5, characterized in that, The diameter of the pores (32) is 20-100 mm, and the spacing of the pores (32) is 2-4 times the diameter; or the length of the vertically distributed pores (32) accounts for 20%-60% of the depth of the injection-production string (3) inserted into the sediment body (2).

7. The compressed gas energy storage system for sludge thermal storage according to claim 1, characterized in that, Multiple injection and production tubing strings (3) are arranged in parallel at intervals. The heads of the multiple injection and production tubing strings (3) are connected to the compressed gas source after merging. The ends of the multiple injection and production tubing strings (3) are respectively inserted into the sediment body (2) in different areas of the underground cavity (1).

8. The compressed gas energy storage system for sludge thermal storage according to claim 1, characterized in that, The compressed gas is one of air, carbon dioxide, nitrogen, oxygen, hydrogen, and ammonia.

9. The compressed gas energy storage system for sludge thermal storage according to any one of claims 1 to 8, characterized in that, The compressed gas energy storage system also includes a heating resistance wire (4) installed in the underground cavity (1), which is used to heat the compressed gas in the underground cavity (1).

10. The compressed gas energy storage system for sludge thermal storage according to any one of claims 1 to 8, characterized in that, The compressed gas energy storage system further includes a heat extraction component, which includes: Gas heat exchange tube (51) is used to connect the underground cavity (1); Liquid heat exchange tube (52) is used to connect to external heating pipes; A heat exchanger (53) is used for heat exchange between the gas heat exchange tube (51) and the liquid heat exchange tube (52).

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