A multi-stage heat storage adsorption-compressed carbon dioxide energy storage system and its operation method

Abstract

This invention proposes a multi-stage heat storage adsorption-compressed carbon dioxide energy storage system and its operation method, belonging to the field of compressed carbon dioxide energy storage. The aim is to solve the problems of low gas density and high energy consumption in existing compressed carbon dioxide energy storage technologies. This invention comprises a low-pressure gas storage unit, a compression unit, an expansion unit, and a waste heat utilization unit. In the low-pressure gas storage unit, a first hot tank and a first cold tank are connected to a low-pressure adsorption tank via heat exchangers. The compression unit includes three compressors and three coolers to compress CO2 to a high-pressure state. The expansion unit includes three expanders and three heaters to convert the high-pressure CO2 energy into other forms of energy. The waste heat utilization unit includes a second hot tank, a second cold tank, and a third hot tank, along with a waste heat utilization device, which can rationally utilize the heat from the final stage of compression. This invention employs a combination of temperature-switching adsorption and heat storage, achieving high-density storage of low-pressure CO2 without introducing external heat, resulting in both high efficiency and energy saving.

Description

Technical Field

[0001] This invention relates to the field of compressed carbon dioxide energy storage, and more particularly to a multi-stage heat storage adsorption compressed carbon dioxide energy storage system and its operation method. Background Technology

[0002] In recent years, the global energy structure has been undergoing profound changes, with renewable energy achieving rapid development due to its clean and sustainable advantages. Energy storage technology, as a key support for ensuring the stable access and efficient utilization of renewable energy, has become a crucial part of national energy strategies.

[0003] Among numerous energy storage technologies, compressed gas energy storage technology has demonstrated strong development potential and rapid growth due to its significant advantages such as large capacity, long cycle life, and fast response speed. Compressed air energy storage technology, as a relatively mature branch, has successfully entered the commercial application stage, providing a feasible solution for large-scale energy storage.

[0004] Meanwhile, compressed carbon dioxide (CO2) energy storage technology is gradually emerging and becoming a research hotspot in the energy storage field. This is because CO2's critical point (7.39 MPa, 31.4℃) is easier to reach than air's (3.77 MPa, -140.5℃), making its operation in energy storage systems more convenient. Furthermore, supercritical CO2 possesses excellent thermodynamic properties, such as low viscosity, high density, and good thermal conductivity, while also being non-toxic and non-flammable, making it a highly promising energy storage medium. Using CO2 as an energy storage medium can significantly improve the energy storage density and operating efficiency of energy storage systems, opening up new paths for the development of energy storage technology.

[0005] Compressed carbon dioxide (CCCO) energy storage systems typically employ a closed-loop system. In this system, gas storage operations are required on both the high-pressure and low-pressure sides, and the choice of storage method directly affects the feasibility and economy of the entire system. Currently, commonly used storage methods include atmospheric pressure gaseous storage, liquid storage, and solid adsorption. However, these methods all have certain limitations: atmospheric pressure gaseous storage, while simple to operate, has low storage density and requires a large amount of space; liquid storage, despite its higher storage density, consumes more energy, increasing operating costs; and adsorption storage, while achieving high storage density, requires a high-temperature heat source, which limits its application scenarios to some extent.

[0006] Furthermore, in some compressed carbon dioxide energy storage systems, the waste heat generated at the final stage of the compressor is not fully and effectively utilized, resulting in energy waste and further reducing the overall efficiency of the system.

[0007] In summary, existing compressed carbon dioxide energy storage technologies still have many problems to be solved in terms of gas storage methods and waste heat utilization, and further improvements and innovations are urgently needed to promote their development towards a more efficient, economical and practical direction. Summary of the Invention

[0008] A brief overview of the invention is given below to provide a basic understanding of certain aspects of it. It should be understood that this overview is not an exhaustive summary of the invention. It is not intended to identify key or essential parts of the invention, nor is it intended to limit the scope of the invention. Its purpose is merely to present certain concepts in a simplified form as a prelude to the more detailed description that follows.

[0009] In view of this, in order to solve the problems of low gas density and high energy consumption in the existing compressed carbon dioxide energy storage technology, the present invention provides a multi-stage heat storage adsorption compressed carbon dioxide energy storage system and its operation method.

[0010] Option 1: A multi-stage heat storage adsorption-compression carbon dioxide energy storage system, comprising a low-pressure gas storage unit, a compression unit, an expansion unit, a waste heat utilization unit, and a high-pressure storage tank.

[0011] The low-pressure gas storage unit includes a first hot tank, a first cold tank, a heat exchanger, and a low-pressure adsorption tank. The first hot tank and the first cold tank are connected to the low-pressure adsorption tank through the heat exchanger.

[0012] The compression unit includes a first compressor, a second compressor, a third compressor, a first cooler, a second cooler, and a third cooler; the first compressor, the first cooler, the second compressor, the second cooler, the third compressor, and the third cooler are connected in sequence; the inlet end of the first compressor is connected to a low-pressure adsorption storage tank, and the outlet end of the third cooler is connected to a high-pressure storage tank.

[0013] The expansion unit includes a first heater, a second heater, a third heater, a first expander, a second expander, and a third expander; the first heater, the first expander, the second heater, the second expander, the third heater, and the third expander are connected in sequence; the outlet end of the high-pressure storage tank is connected to the first heater, and the outlet end of the third expander is connected to the low-pressure adsorption storage tank;

[0014] The waste heat utilization unit includes a second hot tank, a second cold tank, a third hot tank, and a waste heat utilization device; the inlet end of the second hot tank is connected to the first cooler and the second cooler, and the outlet end of the second hot tank is connected to the first heater, the second heater, and the third heater; the inlet end of the second cold tank is connected to the first heater, the second heater, the third heater, and the waste heat utilization device, and the outlet end of the second cold tank is connected to the first cooler, the second cooler, and the third cooler; the inlet end of the third hot tank is connected to the third cooler, and the outlet end is connected to the waste heat utilization device.

[0015] Furthermore, the first compressor, the second compressor, the second expander, and the third expander operate at constant pressure, and the outlet temperatures of the first compressor and the second compressor are equal.

[0016] Furthermore, the third compressor and the first expander operate under sliding pressure, and the outlet pressure of the third compressor and the inlet pressure of the first expander change with the pressure of the high-pressure storage tank.

[0017] Option 2: An operation method for a multi-stage heat storage adsorption-compressed carbon dioxide energy storage system, specifically including the following steps:

[0018] S1. At the start of the energy storage stage, the desorption process takes place in the low-pressure adsorption tank. The heat storage medium flows from the first hot tank to the first cold tank through the heat exchanger. After the adsorbent in the low-pressure adsorption tank absorbs the heat from the first hot tank, the CO2 gas is desorbed from the adsorbent, and the low-pressure CO2 working medium is released from the low-pressure adsorption tank and flows to the compression unit.

[0019] S2. Low-pressure CO2 working fluid enters the compression unit. The CO2 passes through the first compressor, the first cooler, the second compressor, the second cooler, the third compressor, and the third cooler in sequence before entering the high-pressure storage tank. The compression heat of the first compressor and the second compressor is stored in the second heat tank, and the compression heat of the third compressor is stored in the third heat tank.

[0020] S3. As CO2 gas is introduced, the pressure inside the high-pressure storage tank gradually increases, and the energy storage process ends when the target pressure is reached;

[0021] S4. At the beginning of the energy release phase, the high-pressure storage tank slowly releases CO2 working fluid into the expansion unit, and the pressure inside the high-pressure storage tank gradually decreases.

[0022] S5. The CO2 working medium passes through the first heater, the first expander, the second heater, the second expander, the third heater, and the third expander in sequence to expand and do work. After passing through the third expander, the CO2 working medium enters the low-pressure adsorption storage tank. The heat of compression stored in the second heat tank provides heat to the first heater, the second heater, and the third heater, thereby increasing the temperature of the CO2 working medium at the inlet of the first expander, the second expander, and the third expander.

[0023] After the S6.CO2 working medium enters the low-pressure adsorption storage tank, the adsorption process begins. After the heat storage medium enters the first hot tank from the first cold tank through the heat exchanger, the energy release stage ends.

[0024] S7. The compressed heat stored in the third hot tank can be used for local supplemental heating within the system or for supplying living areas via a waste heat utilization device.

[0025] Furthermore, the outlet temperature range of the first and second compressors is 150-250℃, corresponding to a temperature of 130-230℃ for the second hot tank; the outlet temperature range of the third compressor is 70-150℃, corresponding to a temperature of 60-100℃ for the third hot tank; and the temperature of the second cold tank is 40-50℃.

[0026] Furthermore, the working pressure range of the high-pressure storage tank is 6.5-15 MPa.

[0027] The present invention has the following advantages over the prior art:

[0028] 1. This invention adopts a combination of temperature-switching adsorption and heat storage to achieve heat self-sufficiency in the adsorption and desorption process of the adsorbent. It can achieve high-density storage of low-pressure CO2 without the introduction of external heat, which is both efficient and energy-saving.

[0029] 2. In this invention, heat storage is carried out in stages according to the operating temperature, which reduces heat transfer loss and improves system flexibility. It effectively utilizes the heat of compression in the final stage and improves the overall thermal efficiency of the energy storage system.

[0030] 3. This invention has a wide range of applications, requires no special geographical conditions, and can be used for energy storage in conjunction with new energy sources such as wind and solar power, as well as for independent energy storage scenarios;

[0031] 4. This invention can realize combined heat and power, and not only has energy storage function, but can also provide hot water or heating water needed for domestic life in the plant area where the system is located. Attached Figure Description

[0032] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0033] Figure 1 This is a schematic diagram of a multi-stage heat storage adsorption-compressed carbon dioxide energy storage system.

[0034] In the diagram: 1-First hot tank, 2-First cold tank, 3-Heat exchanger, 4-Low-pressure adsorption tank, 5-First compressor, 6-Second compressor, 7-Third compressor, 8-First cooler, 9-Second cooler, 10-Third cooler, 11-High-pressure tank, 12-Second hot tank, 13-Second cold tank, 14-Third hot tank, 15-Waste heat utilization device, 16-First heater, 17-Second heater, 18-Third heater, 19-First expander, 20-Second expander, 21-Third expander. Detailed Implementation

[0035] To make the technical solutions and advantages of the embodiments of the present invention clearer, the exemplary embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not an exhaustive list of all embodiments. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0036] Example 1, Reference Figure 1 This embodiment describes a multi-stage heat storage adsorption-compressed carbon dioxide energy storage system, which includes a low-pressure gas storage unit, a compression unit, an expansion unit, a waste heat utilization unit, and a high-pressure storage tank 11.

[0037] The low-pressure gas storage unit includes a first hot tank 1, a first cold tank 2, a heat exchanger 3, and a low-pressure adsorption storage tank 4. The first hot tank 1 and the first cold tank 2 are connected to the low-pressure adsorption storage tank 4 through the heat exchanger 3.

[0038] The compression unit includes a first compressor 5, a second compressor 6, a third compressor 7, a first cooler 8, a second cooler 9, and a third cooler 10; the first compressor 5, the first cooler 8, the second compressor 6, the second cooler 9, the third compressor 7, and the third cooler 10 are connected in sequence; the inlet end of the first compressor 5 is connected to the low-pressure adsorption storage tank 4, and the outlet end of the third cooler 10 is connected to the high-pressure storage tank 11.

[0039] The expansion unit includes a first heater 16, a second heater 17, a third heater 18, a first expander 19, a second expander 20, and a third expander 21; the first heater 16, the first expander 19, the second heater 17, the second expander 20, the third heater 18, and the third expander 21 are connected in sequence; the outlet end of the high-pressure storage tank 11 is connected to the first heater 16, and the outlet end of the third expander 21 is connected to the low-pressure adsorption storage tank 4;

[0040] The waste heat utilization unit includes a second hot tank 12, a second cold tank 13, a third hot tank 14, and a waste heat utilization device 15; the inlet end of the second hot tank 12 is connected to the first cooler 8 and the second cooler 9, and the outlet end of the second hot tank 12 is connected to the first heater 16, the second heater 17, and the third heater 18; the inlet end of the second cold tank 13 is connected to the first heater 16, the second heater 17, the third heater 18, and the waste heat utilization device 15, and the outlet end of the second cold tank 13 is connected to the first cooler 8, the second cooler 9, and the third cooler 10; the inlet end of the third hot tank 14 is connected to the third cooler 10, and the outlet end is connected to the waste heat utilization device 15.

[0041] Furthermore, the first compressor 5, the second compressor 6, the second expander 20, and the third expander 21 operate at constant pressure, and the outlet temperatures of the first compressor 5 and the second compressor 6 are equal.

[0042] Furthermore, the third compressor 7 and the first expander 19 operate under sliding pressure, and the outlet pressure of the third compressor 7 and the inlet pressure of the first expander 19 change with the pressure of the high-pressure storage tank 11.

[0043] Example 2: An operation method for a multi-stage heat storage adsorption-compressed carbon dioxide energy storage system, specifically including the following steps:

[0044] S1. At the beginning of the energy storage stage, the desorption process takes place in the low-pressure adsorption tank 4. The heat storage medium flows from the first hot tank 1 to the first cold tank 2 through the heat exchanger 3. After the adsorbent in the low-pressure adsorption tank 4 absorbs the heat from the first hot tank 1, the CO2 gas is desorbed from the adsorbent, and the low-pressure CO2 working medium is released from the low-pressure adsorption tank 4 and flows to the compression unit.

[0045] S2. Low-pressure CO2 working fluid enters the compression unit. CO2 passes through the first compressor 5, the first cooler 8, the second compressor 6, the second cooler 9, the third compressor 7 and the third cooler 10 in sequence before entering the high-pressure storage tank 11. The compression heat of the first compressor 5 and the second compressor 6 is stored in the second heat tank 12, and the compression heat of the third compressor 7 is stored in the third heat tank 14.

[0046] S3. As CO2 gas is introduced, the pressure inside the high-pressure storage tank 11 gradually increases, and the energy storage process ends when the target pressure is reached.

[0047] S4. At the beginning of the energy release phase, the high-pressure storage tank 11 slowly releases CO2 working fluid into the expansion unit, and the pressure inside the high-pressure storage tank 11 gradually decreases.

[0048] S5. The CO2 working medium sequentially passes through the first heater 16, the first expander 19, the second heater 17, the second expander 20, the third heater 18, and the third expander 21 to expand and do work. After passing through the third expander 21, the CO2 working medium enters the low-pressure adsorption storage tank 4. The compression heat stored in the second heat tank 12 provides heat to the first heater 16, the second heater 17, and the third heater 18, increasing the CO2 working medium temperature at the inlet of the first expander 19, the second expander 20, and the third expander 21.

[0049] After the S6.CO2 working medium enters the low-pressure adsorption storage tank 4, the adsorption process begins. After the heat storage medium enters the first hot tank 1 from the first cold tank 2 through the heat exchanger 3, the energy release stage ends.

[0050] S7. The compressed heat stored in the third hot tank 14 can be used for local supplemental heating within the system or for supplying living areas via the waste heat utilization device 15.

[0051] Furthermore, the outlet temperature range of the first compressor 5 and the second compressor 6 is 150-250℃, corresponding to a temperature of 130-230℃ for the second hot tank 12; the outlet temperature range of the third compressor 7 is 70-150℃, corresponding to a temperature of 60-100℃ for the third hot tank 14; and the temperature of the second cold tank 13 is 40-50℃.

[0052] Furthermore, the high-pressure storage tank 11 has a working pressure range of 6.5-15 MPa.

[0053] By combining temperature-switching adsorption and heat storage in this invention, the heat of the adsorbent adsorption-desorption process is self-sustaining, and high-density storage of low-pressure CO2 can be achieved without the introduction of external heat, which is both efficient and energy-saving. The staged heat storage according to the operating temperature reduces heat transfer loss and improves system flexibility, effectively utilizes the heat of compression of the last stage, and improves the overall thermal efficiency of the energy storage system.

[0054] This invention enables combined heat and power (CHP) production, which not only has energy storage capabilities but also provides hot water or heating water for the living needs of the plant area where the system is located. This invention has a wide range of applications, does not require special geographical conditions, and can be used for energy storage in conjunction with new energy sources such as wind and solar power, or for independent energy storage scenarios.

[0055] Although the invention has been described with reference to a limited number of embodiments, those skilled in the art will understand from the foregoing description that other embodiments are conceivable within the scope of the invention described herein. Furthermore, it should be noted that the language used in this specification has been chosen primarily for readability and instructional purposes, and not for the purpose of interpreting or limiting the subject matter of the invention. Therefore, many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the appended claims. The disclosure of the invention is illustrative and not restrictive, and the scope of the invention is defined by the appended claims.

Claims

1. A multi-stage heat storage adsorption-compressed carbon dioxide energy storage system, characterized in that, It includes a low-pressure gas storage unit, a compression unit, an expansion unit, a waste heat utilization unit, and a high-pressure storage tank (11); The low-pressure gas storage unit includes a first hot tank (1), a first cold tank (2), a heat exchanger (3), and a low-pressure adsorption tank (4). The first hot tank (1) and the first cold tank (2) are connected to the low-pressure adsorption tank (4) through the heat exchanger (3). The compression unit includes a first compressor (5), a second compressor (6), a third compressor (7), a first cooler (8), a second cooler (9), and a third cooler (10); the first compressor (5), the first cooler (8), the second compressor (6), the second cooler (9), the third compressor (7), and the third cooler (10) are connected in sequence; the inlet end of the first compressor (5) is connected to the low-pressure adsorption tank (4), and the outlet end of the third cooler (10) is connected to the high-pressure tank (11); The expansion unit includes a first heater (16), a second heater (17), a third heater (18), a first expander (19), a second expander (20), and a third expander (21); the first heater (16), the first expander (19), the second heater (17), the second expander (20), the third heater (18), and the third expander (21) are connected in sequence; the outlet end of the high-pressure storage tank (11) is connected to the first heater (16), and the outlet end of the third expander (21) is connected to the low-pressure adsorption storage tank (4); The waste heat utilization unit includes a second hot tank (12), a second cold tank (13), a third hot tank (14), and a waste heat utilization device (15); the inlet end of the second hot tank (12) is connected to the first cooler (8) and the second cooler (9), and the outlet end of the second hot tank (12) is connected to the first heater (16), the second heater (17), and the third heater (18); the inlet end of the second cold tank (13) is connected to the first heater (16), the second heater (17), the third heater (18), and the waste heat utilization device (15), and the outlet end of the second cold tank (13) is connected to the first cooler (8), the second cooler (9), and the third cooler (10); the inlet end of the third hot tank (14) is connected to the third cooler (10), and the outlet end is connected to the waste heat utilization device (15).

2. The multi-stage heat storage adsorption-compressed carbon dioxide energy storage system according to claim 1, characterized in that, The first compressor (5), the second compressor (6), the second expander (20) and the third expander (21) operate at constant pressure, and the outlet temperatures of the first compressor (5) and the second compressor (6) are equal.

3. The multi-stage heat storage adsorption-compressed carbon dioxide energy storage system according to claim 1, characterized in that, The third compressor (7) and the first expander (19) operate under sliding pressure. The outlet pressure of the third compressor (7) and the inlet pressure of the first expander (19) change with the pressure of the high-pressure storage tank (11).

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