Constant-pressure compressed air energy storage device and energy storage system

Abstract

The invention relates to the technical field of energy storage, and discloses a constant-pressure compressed air energy storage device and an energy storage system.The constant-pressure compressed air energy storage device is characterized in that an energy storage library is divided into a first closed cavity and a second closed cavity by a flexible air bag; first fluid is stored in the second closed cavity; the interior of the flexible air bag is communicated with the second closed cavity; during energy storage, compressed air enters the first closed cavity, the flexible air bag is compressed, the size of the first closed cavity is increased, the first fluid in the second closed cavity is compressed and liquefied, and temperature rise and pressure rise of the compressed air are relieved; during energy release, the first fluid is heated, the first fluid absorbs heat to be gasified and transfers heat to the compressed air, the flexible air bag expands, the size of the first closed cavity becomes small, and air is exhausted. During energy storage, gas storage is approximate to constant pressure, temperature and pressure increase of the first closed cavity is slowed down, more air is stored, and power consumption is reduced; and during energy release, temperature and pressure reduction is relieved, approximate constant pressure is achieved, and output air energy is increased.

Description

Technical Field

[0001] The present invention relates to the field of energy storage technology, and in particular to a constant-pressure compressed air energy storage device and an energy storage system. Background Art

[0002] Power storage technology can achieve the regulation of electric energy in time and space, greatly improve the grid connection rate of renewable energy, and enhance the stability and adjustability of renewable energy power systems. It is a key technology of the energy revolution. Compressed air energy storage, as a power storage technology, is similar to pumped storage and has the characteristics of large scale and low cost.

[0003] For the constant volume compressed air energy storage method, an air storage device is generally used; during the energy storage process, as air continuously enters the air storage device, the pressure and temperature inside the air storage device will gradually increase; the increase in pressure increases the power consumption per unit of stored air mass, increases the back pressure of the compressor, deviates from the design operating conditions, and reduces efficiency; the increase in temperature reduces the amount of stored air; during the energy release process, as air continuously flows out of the air storage device, the pressure and temperature inside the air storage device will gradually decrease. After the pressure drops to the inlet pressure of the expander, it cannot meet the full power generation of the expander. The temperature decreases and accelerates the pressure drop, limiting the total output power of the expander, and seriously reducing the energy storage efficiency and energy storage density of the entire energy storage system. Summary of the invention

[0004] In view of this, the present invention provides a constant-pressure compressed air energy storage device to solve the existing constant-volume compressed air energy storage. During the energy storage process, as air continuously enters the gas storage device, the pressure and temperature inside the gas storage device will gradually increase; the pressure increase increases the power consumption per unit gas storage mass, increases the compressor back pressure, deviates from the design operating conditions, and reduces efficiency; the temperature increase reduces the gas storage volume; during the energy release process, as air continuously flows out of the gas storage device, the pressure and temperature inside the gas storage device will gradually decrease. After the pressure is reduced to the inlet pressure of the expander, it is unable to meet the full power generation of the expander. The temperature decreases and accelerates the pressure decrease, limiting the total output power of the expander, and seriously reducing the energy storage efficiency and energy storage density of the entire energy storage system.

[0005] In a first aspect, the present invention provides a constant pressure compressed air energy storage device, comprising: The energy storage reservoir is internally divided into a first closed cavity and a second closed cavity; the first closed cavity is provided with an air inlet and an air outlet; a first fluid is stored in the second closed cavity; At least one flexible airbag is located in the first closed cavity, and the flexible airbag divides the interior of the energy storage reservoir into a first closed cavity and a second closed cavity; the interior of the flexible airbag is connected to the second closed cavity; A heater, disposed in the second closed cavity; The constant-pressure compressed air energy storage device has a state in which compressed air enters the first closed cavity through the air inlet, compresses the flexible airbag, the volume of the first closed cavity increases, and the first fluid in the second closed cavity is pressurized and liquefied, thereby alleviating the energy storage state of the compressed air heating and pressure increase; and has an energy release state in which the heater heats the first fluid, the first fluid absorbs heat and vaporizes, further transfers heat to the compressed air, heats the compressed air, expands the flexible airbag, the volume of the first closed cavity decreases, and the compressed air is discharged through the air outlet. Beneficial effects: The present application adopts the above technical solution. In the energy storage process, the flexible airbag is compressed by compressed air, so that the first fluid inside the flexible airbag is pressurized and liquefied, and at the same time, the heat of the compressed air inside the first closed cavity is absorbed by heat transfer, the effective gas storage volume of the first closed cavity becomes larger, the gas storage process is approximately a constant pressure process, the increase of the temperature and pressure in the first closed cavity is slowed down, and the first closed cavity can store more compressed air, that is, the gas storage capacity is improved, while the compression power consumption is reduced, and the operating efficiency of the compressor under variable working conditions is avoided; in the energy release process, the heater heats the first fluid, and the first fluid in the second closed cavity absorbs heat and vaporizes. On the one hand, the space occupied by the flexible airbag becomes larger, and on the other hand, the heat of the first fluid is transferred to the compressed air through the flexible airbag, slowing down the decrease in the temperature and pressure in the first closed cavity. Under the dual effects of volume reduction and heat input, the temperature and pressure reduction trend in the first closed cavity is alleviated, and an energy release process approximately at constant pressure can be achieved, increasing the energy of the output compressed air. The compressed air at the bottom of the first closed cavity is reduced, and the compressed air in the first closed cavity is more effectively utilized.

[0006] Optionally, the boiling point of the first fluid ranges from 30°C to 70°C.

[0007] Optionally, the first fluid is carbon dioxide.

[0008] Optionally, a first valve is provided at the air inlet of the first closed cavity; and a regulating valve is provided at the air outlet of the first closed cavity. Beneficial effects: The present application adopts the above technical solution, and the first valve is used to conveniently switch on and off the input of compressed air; and the regulating valve is used to conveniently adjust the air inlet pressure of the subsequent expander.

[0009] Optionally, when electricity consumption is low, the constant-pressure compressed air energy storage device is in an energy storage state; when electricity consumption is peak, the constant-pressure compressed air energy storage device is in an energy release state.

[0010] In a second aspect, the present invention further provides an energy storage system, comprising: the above-mentioned constant-pressure compressed air energy storage device.

[0011] Optionally, it also includes: At least two compressors connected in sequence are connected to the air inlet of the first closed cavity; the compressors are suitable for compressing air; At least two expansion machines are connected in sequence and are connected to the gas outlet of the first closed cavity.

[0012] Optionally, the heater is a heat exchange coil.

[0013] Optionally, it also includes: at least one cooler, in which a second fluid flows; the cooler is suitable for recovering compression heat of the compressor to heat the second fluid; a heat storage structure connected to the cooler, wherein the heat storage structure is suitable for storing the heated second fluid; At least one reheater connected to the heat storage structure; the reheater is suitable for heating the intake air of the expander through the second fluid transported by the heat storage structure; the output end of the reheater is connected to the input end of the heat exchange coil; The cold storage structure is connected to the output end of the heat exchange coil, and the cold storage structure is connected to the cooler; the cold storage structure is suitable for storing the cooled second fluid and delivering the cooled second fluid to the cooler. Beneficial effect: The present application adopts the above technical solution, and on the basis of realizing constant pressure energy storage and energy release, realizes the effective recovery and utilization of the low-temperature waste heat of the second fluid output by the reheater, reduces energy loss, breaks through the limitations of the energy storage efficiency and energy storage density of the existing constant volume compressed air energy storage, and further increases the energy storage efficiency and energy storage density of the entire energy storage system.

[0014] Optionally, a first power pump and a second valve connected in sequence are provided on the pipeline connecting the heat storage structure and the reheater; a second power pump and a third valve connected in sequence are provided on the pipeline connecting the cold storage structure and the cooler. Beneficial effect: The present application adopts the above technical solution, and improves the delivery power through the first power pump and the second power pump; and conveniently controls the on-off of the circulation of the second fluid through the second valve and the third valve. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 A connection diagram of an energy storage system provided in an embodiment of the present invention.

[0017] Description of reference numerals: 1. Energy storage tank; 2. First fluid; 3. Flexible airbag; 4. First valve; 5. Control valve; 6. Compressor; 7. Expander; 8. Heat exchange coil; 9. Cooler; 10. Heat storage structure; 11. Reheater; 12. Cold storage structure; 13. First power pump; 14. Second valve; 15. Second power pump; 16. Third valve. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0019] For the constant volume compressed air energy storage method using fluid heat storage, the temperature of the hot fluid after heating the compressed air in the reheater is generally ≥30°C, that is, the hot fluid after use still contains a lot of heat that is not effectively utilized, resulting in low-temperature energy loss. In addition, the constant volume compressed air energy storage method using fluid heat storage usually uses cold fluid storage devices and hot fluid storage devices, which significantly increases the energy storage cost. It is also due to the above reasons that the present application proposes a constant pressure compressed air energy storage device and energy storage system.

[0020] like Figure 1 A specific implementation of the constant pressure compressed air energy storage device shown includes: an energy storage reservoir 1, at least one flexible air bag 3 and a heater.

[0021] The interior of the energy storage reservoir 1 is divided into a first closed cavity and a second closed cavity; the first closed cavity is provided with an air inlet and an air outlet; the first closed cavity is suitable for storing high-pressure compressed air. Further, a first valve 4 is provided at the air inlet of the first closed cavity, specifically, the first valve 4 is a switch valve; a regulating valve 5 is provided at the air outlet of the first closed cavity, and the regulating valve 5 is used to adjust the air intake of the subsequent expansion machine 7. A first fluid 2 is stored in the second closed cavity; specifically, the first fluid 2 is a low-boiling point fluid, and the boiling point range of the first fluid 2 is 30°C to 70°C; the first fluid 2 can be a low-boiling point working fluid such as carbon dioxide. Six flexible airbags 3 are located in the first closed cavity, and the flexible airbags 3 divide the interior of the energy storage reservoir 1 into a first closed cavity and a second closed cavity; the interior of the flexible airbags 3 is connected to the second closed cavity. The heater is arranged in the second closed cavity; specifically, the heater can be a heat exchange coil 8. The constant-pressure compressed air energy storage device has a state in which compressed air enters the first closed cavity through the air inlet, compresses the flexible airbag 3, the volume of the first closed cavity increases, and the first fluid 2 in the second closed cavity is pressurized and liquefied, thereby alleviating the energy storage state of the compressed air heating and pressure increase; and has an energy release state in which the heater heats the first fluid 2, the first fluid 2 absorbs heat and vaporizes, further transfers heat to the compressed air, heats the compressed air, the flexible airbag 3 expands, the volume of the first closed cavity decreases, and the compressed air is discharged through the air outlet. Specifically, during low electricity consumption, the constant-pressure compressed air energy storage device is in an energy storage state; during peak electricity consumption, the constant-pressure compressed air energy storage device is in an energy release state.

[0022] like Figure 1 A specific embodiment of the energy storage system shown includes: the constant pressure compressed air energy storage device, at least two-stage compressors 6 connected in sequence, at least two-stage expanders 7 connected in sequence, at least one cooler 9, a heat storage structure 10, at least one reheater 11 and a cold storage structure 12.

[0023] The second-stage compressor 6 connected in sequence is connected to the air inlet of the first closed cavity; the compressor 6 is suitable for compressing air, Figure 1 The arrow on the upper left of the left compressor 6 indicates the air intake, and the subsequent arrows indicate the flow direction of the air intake or compressed air. The second-stage expander 7 connected in sequence is connected to the air outlet of the first closed cavity, Figure 1The arrow at the lower left of the left expander 7 indicates exhaust. After the compressed air output from the air outlet of the first closed cavity passes through the nozzle, the air flow rate increases, driving the impeller of the expander 7 to rotate, and converting the pressure of the compressed air into the kinetic energy of the expander 7. A second fluid flows inside the two coolers 9; the cooler 9 is suitable for recovering the compression heat of the compressor 6 to heat the second fluid; specifically, the cooler 9 exchanges heat with the outlet pipeline of the compressor 6. The heat storage structure 10 is connected to the cooler 9, and the heat storage structure 10 is suitable for storing the heated second fluid. Two reheaters 11 are connected to the heat storage structure 10; the reheater 11 is suitable for heating the intake air of the expander 7 through the second fluid transported by the heat storage structure 10; specifically, the reheater 11 exchanges heat with the intake pipeline of the expander 7. The output end of the reheater 11 is connected to the input end of the heat exchange coil 8. The cold storage structure 12 is connected to the output end of the heat exchange coil 8 , and the cold storage structure 12 is connected to the cooler 9 ; the cold storage structure 12 is suitable for storing the cooled second fluid and conveying the cooled second fluid to the cooler 9 .

[0024] Furthermore, a first power pump 13 and a second valve 14 are provided in sequence on the pipeline connecting the heat storage structure 10 and the reheater 11; a second power pump 15 and a third valve 16 are provided in sequence on the pipeline connecting the cold storage structure 12 and the cooler 9. Specifically, the second valve 14 and the third valve 16 are both switch valves; the first power pump 13 and the second power pump 15 are both circulation pumps.

[0025] The principle of the energy storage system described in this application is briefly described as follows: When the power consumption is low, the low-valley electricity drives the compressor 6 through the electric motor, and the air is compressed to a high-pressure state by multi-stage compression and inter-stage cooling. After the high-pressure air is cooled, it is stored in the first closed cavity. At the same time, the second fluid in the cold storage structure 12 enters the two coolers 9, recovers the compression heat of the secondary compressor 6, and stores the compression heat in the heat storage structure 10. The flexible airbag 3 is compressed, and the gaseous low-boiling point first fluid 2 is liquefied, while releasing the gas storage space of the first closed cavity, the temperature of the compressed air in the first closed cavity is reduced. At the peak of power consumption, the second fluid stored in the heat storage structure 10 enters the reheater 11 for heating the compressed air. The high-pressure air in the first closed cavity enters the reheater 11 through the regulating valve 5 to heat up, and the high-temperature and high-pressure air after heating enters the expander 7, and the expander 7 converts the pressure energy in the air into mechanical energy, and the mechanical energy of the expander 7 generates electricity through the generator. The low-temperature heat-storing second fluid output from the reheater 11 enters the heat exchange coil 8, and transfers the heat to the low-boiling-point first fluid 2. The low-boiling-point first fluid 2 is vaporized by the heat, the flexible airbag 3 is expanded, the air storage space in the first closed cavity is occupied, and the low-temperature waste heat of the first fluid 2 is further transferred to the internal air of the first closed cavity.

[0026] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A constant pressure compressed air energy storage device, characterized in that: include: An energy storage reservoir (1) is internally divided into a first closed cavity and a second closed cavity; the first closed cavity is provided with an air inlet and an air outlet; a first fluid (2) is stored in the second closed cavity; At least one flexible airbag (3) is located in the first closed cavity, and the flexible airbag (3) divides the interior of the energy storage reservoir (1) into a first closed cavity and a second closed cavity; the interior of the flexible airbag (3) is in communication with the second closed cavity; A heater, disposed in the second closed cavity; The constant-pressure compressed air energy storage device has an energy storage state in which compressed air enters the first closed cavity through the air inlet, compresses the flexible airbag (3), the volume of the first closed cavity increases, and the first fluid (2) in the second closed cavity is pressurized and liquefied, thereby alleviating the compressed air from heating and pressure increase; and an energy release state in which the heater heats the first fluid (2), the first fluid (2) absorbs heat and vaporizes, further transfers heat to the compressed air, heats the compressed air, the flexible airbag (3) expands, the volume of the first closed cavity decreases, and the compressed air is discharged through the air outlet.

2. The constant pressure compressed air energy storage device according to claim 1, characterized in that: The boiling point of the first fluid (2) is in the range of 30°C to 70°C.

3. The constant pressure compressed air energy storage device according to claim 2, characterized in that: The first fluid (2) is carbon dioxide.

4. The constant pressure compressed air energy storage device according to claim 1, characterized in that: A first valve (4) is provided at the air inlet of the first closed cavity; and a regulating valve (5) is provided at the air outlet of the first closed cavity.

5. The constant pressure compressed air energy storage device according to any one of claims 1 to 4, characterized in that: When electricity consumption is low, the constant-pressure compressed air energy storage device is in an energy storage state; when electricity consumption is peak, the constant-pressure compressed air energy storage device is in an energy release state.

6. An energy storage system, characterized in that: include: The constant pressure compressed air energy storage device according to any one of claims 1 to 5.

7. The energy storage system according to claim 6, characterized in that: Also includes: At least two compressors (6) connected in sequence are connected to the air inlet of the first closed cavity; the compressor (6) is suitable for compressing air; At least two expansion machines (7) are connected in sequence and are connected to the gas outlet of the first closed cavity.

8. The energy storage system according to claim 7, characterized in that: The heater is a heat exchange coil (8).

9. The energy storage system according to claim 8, characterized in that: Also includes: at least one cooler (9) having a second fluid flowing therein; the cooler (9) is suitable for recovering compression heat of the compressor (6) to heat the second fluid; A heat storage structure (10) connected to the cooler (9), wherein the heat storage structure (10) is suitable for storing the heated second fluid; at least one reheater (11) connected to the heat storage structure (10); the reheater (11) is suitable for heating the intake air of the expander (7) through the second fluid transported by the heat storage structure (10); the output end of the reheater (11) is connected to the input end of the heat exchange coil (8); A cold storage structure (12) is connected to the output end of the heat exchange coil (8), and the cold storage structure (12) is connected to the cooler (9); the cold storage structure (12) is suitable for storing the cooled second fluid and delivering the cooled second fluid to the cooler (9).

10. The energy storage system according to claim 9, characterized in that: A first power pump (13) and a second valve (14) connected in sequence are provided on a pipeline connecting the heat storage structure (10) and the reheater (11); and a second power pump (15) and a third valve (16) connected in sequence are provided on a pipeline connecting the cold storage structure (12) and the cooler (9).

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