Energy storage devices and expanders
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- HITACHI IND EQUIP SYST CO LTD
- Filing Date
- 2025-01-24
- Publication Date
- 2026-08-05
Smart Images
Figure 2026126765000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to an energy storage device, particularly an expander used in a compressed air energy storage device, a liquid air energy storage device, and devices thereof.
Background Art
[0002] Power generation using renewable energy such as wind power generation and solar power generation depends on weather conditions, so the power generation amount may fluctuate and may not be stable. For such fluctuations, a compressed air energy storage (CAES) system or a liquid air energy storage (LAES) system is known as a system for leveling the power generation output.
[0003] An energy storage device using this CAES system and LAES system stores electrical energy as compressed air or liquefied air in a tank, and when power is required, the stored air drives an expander to operate a generator to generate electrical energy and level the output.
[0004] For example, in a CAES device, in order to improve the power generation efficiency, a system is known in which compressed heat is recovered by a heat storage medium, stored in a heat storage tank or the like, and the compressed air before expansion is heated using the recovered compressed heat. Thereby, heat radiation during storage in the accumulator tank is reduced, and the recovered power during expansion is increased.
[0005] As a CAES device that performs such heat recovery, Patent Document 1 discloses a compressed air storage power generation device comprising: an electric compressor that compresses air using electricity; a pressure accumulator that stores the compressed air discharged from the electric compressor; an expansion generator that generates electricity by expanding the compressed air supplied from the pressure accumulator; a first water storage section and a second water storage section that store liquid water and are fluidly connected to each other; a first heat exchanger that exchanges heat between the compressed air flowing from the electric compressor to the pressure accumulator and the water flowing from the first water storage section to the second water storage section to cool the compressed air and heat the water; and a second heat exchanger that exchanges heat between the compressed air flowing from the pressure accumulator to the expansion generator and the water flowing from the second water storage section to the first water storage section to heat the compressed air and cool the water. [Prior art documents] [Patent Documents]
[0006] [Patent Document 1] Patent No. 6913044 [Overview of the project] [Problems that the invention aims to solve]
[0007] CAES and LAES systems require a high ratio of output energy generated by driving the expander to input energy during compressed air generation (power recovery efficiency). Therefore, the power generation efficiency of the expander used for power generation is crucial. However, while Patent Document 1 attempts to improve power generation efficiency by heating the compressed air in the accumulator with a second heat exchanger and supplying it to the expansion generator, it does not particularly consider improving the performance of the expander itself, such as its thermal insulation, to enhance power generation efficiency.
[0008] The present invention aims to improve power generation efficiency by enhancing the performance of the expander. [Means for solving the problem]
[0009] The present invention includes several means for solving the above problems, but to give one example, a compressor for compressing air, a supply pump for supplying a liquid medium, a first heat exchanger for exchanging heat between the air compressed by the compressor and the liquid medium supplied by the supply pump, a pressure storage tank for storing the air after heat exchange in the first heat exchanger, a heat storage tank for storing the liquid medium after heat exchange in the first heat exchanger, and the air stored in the pressure storage tank and the liquid medium stored in the heat storage tank. The energy storage device is characterized by comprising: a second heat exchanger that exchanges heat with the air; an expander driven by the air that has undergone heat exchange in the second heat exchanger; an air supply pipe connected to the pressure accumulator and the expander via the second heat exchanger, which supplies air supplied from the pressure accumulator to the expander; and a liquid supply pipe connected to the liquid supply pump and the expander via the first heat exchanger and the heat accumulator, which supplies a liquid medium supplied from the liquid supply pump to the expander. [Effects of the Invention]
[0010] According to the present invention, the performance of the expander can be improved, thereby increasing power generation efficiency. [Brief explanation of the drawing]
[0011] [Figure 1] This is a schematic diagram of a compressed air energy storage device according to Embodiment 1 of the present invention. [Figure 2] This is a cross-sectional view showing an expander according to Embodiment 1 of the present invention. [Figure 3] This is a cross-sectional view showing another expander according to Embodiment 1 of the present invention. [Figure 4] A cross-sectional view showing yet another expander of the present invention, Example 1. [Figure 5] This is a schematic diagram of a compressed air energy storage device according to Embodiment 2 of the present invention. [Figure 6] This is a cross-sectional view showing an expander according to Embodiment 2 of the present invention. [Figure 7] Figure 6 is a cross-sectional view of the expander AA. [Figure 8]This is a schematic configuration diagram of a compressed air energy storage device according to Example 3 of the present invention. [Figure 9] This is a schematic configuration diagram of a compressed air energy storage device according to Example 4 of the present invention. [Figure 10] This is a schematic configuration diagram of a compressed air energy storage device according to Example 5 of the present invention. [Figure 11] This is a schematic configuration diagram of a compressed air energy storage device according to Example 6 of the present invention. [Figure 12] This is a schematic configuration diagram of a liquid air energy storage device according to Example 7 of the present invention. [Figure 13] This is a schematic configuration diagram of a liquid air energy storage device according to Example 8 of the present invention. [Figure 14] This is a schematic configuration diagram of a liquid air energy storage device according to Example 9 of the present invention. [Figure 15] This is a schematic configuration diagram of a liquid air energy storage device according to Example 10 of the present invention [Figure 16] \ This is a schematic configuration diagram of a liquid air energy storage device according to Example 11 of the present invention. [Figure 17] This is a schematic configuration diagram of a liquid air energy storage device according to Example 12 of the present invention.
Mode for Carrying Out the Invention
[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same or similar elements and processes are denoted by the same reference numerals, and redundant description is omitted.
[0013] ≪Example 1≫ FIG. 1 shows a schematic configuration diagram of a compressed air energy storage device 1-1 (hereinafter referred to as CAES device 1-1) according to Example 1 of the present invention. The CAES device 1-1 includes a compressor unit 1A having motors (electric motors) 4 and 5, compressors 6 and 7, and a pressure accumulator tank 8, an expander unit 1B having expanders 10 and 11, and generators 12 and 13, and a heat storage unit 1C having heat storage tanks 21 and 22, heat exchangers 24, 25, 2, and transfer pumps 28 and 29.
[0014] The heat storage unit 1C is a system in which water, which is a liquid heat storage medium (liquid medium), circulates. In the CAES device 1-1 of the first embodiment, an air supply pipe 17 is provided which is connected to the accumulator tank 8 and the expander 10 via the heat exchanger 26 and supplies the air supplied from the accumulator tank 8 to the expander 10. Further, in the CAES device 1-1 of the first embodiment, a liquid supply pump 30 for supplying water as the heat storage medium is provided, and a liquid supply pipe 31 (31a, 31b) is provided which is connected to the liquid supply pump 30 and the expanders 10, 11 via the heat exchangers 24, 25 and the heat storage tanks 21, 22 and supplies the water supplied from the liquid supply pump 30 to the expanders 10, 11. Furthermore, in the CAES device 1-1 of the first embodiment, liquid supply branch pipes 32a, 32b are provided which branch from the liquid supply pipe 31 and supply the water supplied from the heat storage tank 21 to the heat exchangers 26, 27. The water supplied to the heat exchangers 26, 27 via the liquid supply branch pipes 32a, 32b flows into the second tank 22.
[0015] The CAES device 1-1 is connected to grid power 20 that utilizes renewable energy such as a solar power generation device 18 and a wind power generation device 19. Specifically, the motors 4, 5 of the compressor unit 1A are connected to the grid power 20 via the inverter device 9, and the generators 12, 13 of the expander unit 1B are connected to the grid power 20 via the power conditioner 14.
[0016] In the compressor unit 1A, the motor 4 is mechanically connected to the screw compressor 6, and the first-stage compression stroke is performed by rotationally driving the compressor 6 by the motor 4. The motor 5 is mechanically connected to the screw compressor 7, and the second-stage compression stroke is performed by rotationally driving the compressor 7 by the motor 5. Two-stage compression of air is performed by these compressors 6, 7.
[0017] Also, the suction port of the first-stage compressor 6 opens to the atmosphere, and the discharge port of the compressor 6 is connected to the suction port of the second-stage compressor 7 via the heat exchanger 24 of the heat storage unit 1C. The discharge port of the compressor 7 is connected to the accumulator tank 8 via the heat exchanger 25 of the heat storage unit 1C.
[0018] The expander unit 1B has an expander 10 that performs the first stage expansion stroke and an expander 11 that performs the second stage expansion stroke, and these expanders 10 and 11 perform a two-stage expansion of compressed air. The inlet pipe 10a, which is the air inlet of the first stage expander 10, is connected to the accumulator tank 8 of the compressor unit 1A by the supply air pipe 17. During the expansion stroke (discharge operation), an on-off valve 15 provided in the supply air pipe 17, which is downstream of the accumulator tank 8 and upstream of the heat exchanger 26, is opened, and the compressed air stored in the accumulator tank 8 is supplied to the expander 10 through the heat exchanger 26.
[0019] Furthermore, the discharge port of the expander 10 is connected to the inlet pipe 11a, which is the air inlet of the second-stage expander 11, via the heat exchanger 27 of the heat storage unit 1C, and the discharge port of the expander 11 opens to the atmosphere.
[0020] Furthermore, generators 12 and 13 are mechanically connected to their respective expanders 10 and 11. In the two-stage expansion stroke described above, generators 12 and 13 are rotated by expanders 10 and 11 to generate electricity (power regeneration), and the regenerated power is returned to grid power 20 via power conditioner 14.
[0021] The heat storage unit 1C has a high-temperature heat storage tank (hereinafter referred to as the first tank) 21 for storing water, which is the heat storage medium, and a low-temperature heat storage tank (hereinafter referred to as the second tank) 22. The water in the second tank 22 is transferred by a transfer pump 29 and flows into the first tank via heat exchangers 24 and 25, which are connected in parallel to each other. The water in the first tank 21 is transferred by a transfer pump 28. The water transferred by the pump 28 is transferred (to the liquid supply pipes 31a and 31b, and) via the liquid supply branch pipes 32a and 32b to heat exchangers 26 and 27, which are connected in parallel to each other, and flows into the second tank 22.
[0022] More specifically, the water in the second tank 22 is heated in heat exchangers 24 and 25 by heat exchange with compressed air discharged from compressors 6 and 7. The heated, high-temperature water is stored in the first tank 21. The water stored in the first tank 21 is transferred to heat exchangers 26 and 27 via the supply branch pipes 32a and 32b. The transferred water is cooled in heat exchangers 26 and 27 by heat exchange with compressed air just before it flows into the expanders 10 and 11. The cooled, low-temperature water is stored in the second tank 22. The water in the heat storage unit 1C is replenished as needed by the supply pump 30. The supply pump 30 also maintains the water pressure in the heat storage unit 1C at a predetermined pressure, i.e., a pressure higher than the air stored in the pressure storage tank 8.
[0023] The supply liquid pump 30 and the expanders 10 and 11 are connected to supply liquid pipes 31 (31a, 31b) via heat exchangers 24 and 25 and heat storage tanks (first tank 21, second tank 22). More specifically, one end of the supply liquid pipes 31, 31a, 31b, is connected to the inlet pipes 10a, 11a of the expanders 10 and 11. The supply liquid pipes 31 allow high-temperature water stored in the first tank 21 to be supplied to the inlet pipes 10a, 11a of the expanders 10 and 11, respectively. In addition, flow control valves 33a, 33b are provided on the supply liquid pipes 31a, 31b to adjust the flow rate of water passing through the supply liquid pipes 31a, 31b.
[0024] Figure 2 shows a cross-sectional view of the expander 10. The expander 10 is a screw expander, and its expansion mechanism 101 comprises a main casing 102 having a cylindrical casing bore 104, and a male rotor 106 and a female rotor (not shown) arranged inside the main casing 102. The rotation shaft 115 of the male rotor 106 is rotatably supported by bearings 115a and 115b, and the female rotor, which is arranged to mesh with the male rotor 106, is also rotatably supported by bearings. A generator 12 is connected to one end of the rotation shaft 115 of the male rotor 106 in the axial direction.
[0025] Furthermore, within the main casing 102, multiple spaces (operating chambers) are formed, surrounded by the casing bore 104, the male rotor 106, and the female rotor. The expansion of air flowing into the operating chamber from the intake port 111 of the casing bore 104 rotates the male rotor 106 and the female rotor 107, and consequently, the generator 12 connected to the rotation shaft 115 of the male rotor 106 also rotates to generate electricity.
[0026] Furthermore, the inlet pipe 10a of the expander 10 is connected to the main casing 102, and the main casing 102 has a suction passage 113 that connects the inlet pipe 10a to a suction port 111 that opens into the casing bore 104. Compressed air supplied from the accumulator tank 8 to the inlet pipe 10a during the expansion stroke flows into the casing bore 104 through this suction passage 113.
[0027] Furthermore, a liquid supply pipe 31a is connected to the upper part of the inlet pipe 10a of the expander 10 so as to communicate with the inlet pipe 10a, and this liquid supply pipe 31a is configured to supply high-temperature water stored in the first tank 21 of the heat storage unit 1C to the inlet pipe 10a.
[0028] The expander 11 is a screw expander having the same configuration as the expander 10, and the liquid supply piping 31b is connected to the inlet piping 11a of the expander 11 so that high-temperature water from the first tank 21 can be supplied.
[0029] Next, the charging and discharging operations of CAES device 1-1 will be described.
[0030] (during charging operation) First, the charging operation of the CAES device 1-1, which generates and stores compressed air in the compressor unit 1A, will be explained. When power from grid power 20, which utilizes renewable energy, etc., is input to motors 4 and 5 via the inverter device 9, this input power rotates motors 4 and 5, and at the same time drives compressors 6 and 7 connected to motors 4 and 5, performing two-stage compression of air. Specifically, in terms of airflow, compressor 6 draws in atmospheric air from its intake and performs adiabatic compression (first stage), and the compressed air discharged from the outlet of compressor 6 flows into compressor 7 via the heat exchanger 24, where it is further adiabatic compressed (second stage). The air compressed in this two-stage process is stored in the accumulator tank 8 via the heat exchanger 25.
[0031] During this charging operation, the transfer pump 29 of the heat storage unit 1C is activated, supplying water stored in the second tank 22 on the low-temperature side to the heat exchangers 24 and 25. The water supplied to the heat exchanger 24 is heated to a high temperature by heat exchange with the high-temperature compressed air adiabatically compressed (first stage) by the compressor 6, and flows from the heat exchanger 24 to the first tank 21 on the high-temperature side for storage.
[0032] Furthermore, through heat exchange in the heat exchanger 24, the compressed air is cooled to approximately room temperature before flowing into the compressor 7. There, it undergoes adiabatic compression (second stage) in the compressor 7, becoming even more high-pressure and hotter before flowing into the heat exchanger 25. The water supplied from the second tank 22 to the heat exchanger 25 is heated to a high temperature through heat exchange with the high-pressure, high-temperature compressed air, and is stored in the high-temperature first tank 21 from the heat exchanger 25. Meanwhile, the compressed air is cooled again to approximately room temperature before flowing into the pressure accumulator 8 for storage. In this manner, compressed air energy is stored during charging operations, and high-temperature water is stored in the first tank 21 of the heat storage unit 1C.
[0033] Furthermore, the air compressed and discharged by compressors 6 and 7 reaches a high temperature of approximately 160-170°C when compressed to, for example, 1 MPa. Therefore, it is preferable that the water that exchanges heat with this air is pressurized so that its saturation temperature is raised to a level higher than the discharge air temperature of compressors 6 and 7. In other words, when supplying liquid to the circuit of the heat storage unit 1C, it is preferable to pressurize the water with the supply pump 30 and maintain a higher pressure than the air stored in the pressure storage tank 8. For example, if the water is pressurized to the same 1 MPa as the discharge air of the compressor, its saturation temperature will rise to approximately 180°C, thereby enabling the water to exchange heat with the discharge air and store heat without boiling.
[0034] (During discharge operation) Next, we will explain the discharge operation of the CAES device 1-1, which generates electricity by driving generators 12 and 13 with compressed air using the expander unit 1B.
[0035] The expanders 10 and 11 are driven by opening the on / off valve 15 and supplying compressed air stored in the accumulator tank 8 to the expanders 10 and 11. Specifically, the compressed air from the accumulator tank 8 flows through the air supply pipe 17 into the inlet pipe 10a of the expander 10, and is driven by adiabatic expansion (first stage) in the expander 10. Furthermore, the compressed air discharged from the outlet of the expander 10 flows through the heat exchanger 27 into the inlet pipe 11a of the expander 11, and is driven by further adiabatic expansion (second stage) in the expander 11. The air expanded in the expander 11 becomes low temperature and low pressure and is released into the atmosphere from the outlet of the expander 11.
[0036] In this manner, when the expanders 10 and 11 are driven, the generators 12 and 13 connected to the expanders 10 and 11 are rotated to generate electricity, and the generated electricity is supplied to the grid power 20 via the power conditioner 14. In this way, the stored compressed air energy is regenerated.
[0037] During this discharge operation, the transfer pump 28 of the heat storage unit 1C is activated, causing the high-temperature water stored in the first tank 21 to be transferred to the heat exchangers 26 and 27 via the liquid supply branch pipes 32a and 32b, and also to the expanders 10 and 11 via the liquid supply pipes 31a and 31b. Here, the water in the heat storage unit 1C is maintained at the same pressure as, or higher than, the compressed air in the accumulator tank 8 by the liquid supply pump 30. Therefore, as the high-temperature water from the first tank 21 flows into the heat exchangers 26 and 27, a portion of the high-temperature water can be injected into the inlet pipes 10a and 11a of the expanders 10 and 11 via the liquid supply pipes 31a and 31b. At this time, by adjusting the flow rate of water passing through the liquid supply pipes 31a and 31b using the flow control valves 33a and 33b, it is possible to inject a desired amount of high-temperature water from the liquid supply pipes 31a and 31b into the inlet pipes 10a and 11a.
[0038] The high-temperature water flowing from the first tank 21 through the supply branch pipes 32a and 32b into the heat exchangers 26 and 27 exchanges heat with the compressed air just before it flows into the inlet pipes 10a and 11a of the expander 10, heating the compressed air. The heated compressed air then flows into the expanders 10 and 11 and expands, improving expansion and power generation efficiency.
[0039] Furthermore, the high-temperature water injected from the liquid supply pipe 31a into the inlet pipe 10a of the expander 10 mixes with the compressed air flowing from the heat exchanger 26 into the inlet pipe 10a, as shown in Figure 2, raising the temperature of the inlet air of the expander 10. It then flows through the suction passage 113 into the casing bore 104 from the intake port 111 while still mixed with the compressed air, and is subsequently discharged from the discharge port 112 along with the air.
[0040] Similarly, the high-temperature water injected from the liquid supply pipe 31b into the inlet pipe 11a of the expander 11 flows into the expander 11 mixed with the compressed air flowing from the heat exchanger 27 into this inlet pipe 11a, and is then discharged from the outlet of the expander 11 together with the air.
[0041] Next, we will explain how to improve the power generation efficiency of the expanders 10 and 11.
[0042] Since the high-temperature water injected from the supply pipes 31a and 31b into the inlet pipes 10a and 11a of the expanders 10 and 11 is a liquid, when this water flows into the working chambers of the expanders 10 and 11 while mixed with compressed air, it adheres to the surfaces of each component forming the working chambers (casing bore, male rotor and female rotor, etc.). This not only improves the sealing performance between the working chambers and reduces air leakage, but also improves the lubrication of the rotors, which are rotationally driven by the expansion of compressed air. Consequently, the flow rate of compressed air, which is the working fluid of the expanders, increases, and the overall adiabatic efficiency of the expanders improves, thereby improving the expansion efficiency and increasing the amount of power generated. In other words, the performance (sealing performance and lubrication) of the expanders 10 and 11 can be improved, thereby improving power generation efficiency.
[0043] Furthermore, the compressed air in the accumulator tank 8 is not only heated by the heat exchangers 26 and 27, but is also further heated by the injection of high-temperature water from the feed pipes 31a and 31b before flowing into the working chambers of the expanders 10 and 11. As a result, the expansion stroke of the air within the expanders 10 and 11 can be brought closer to isothermal expansion than isentropic expansion, which makes it possible to feed the increase in the internal energy of the expanded air into the generators 12 and 13 as output from the expanders 10 and 11. Consequently, it is possible to further increase the amount of power generated.
[0044] Furthermore, by directly injecting high-temperature water from the liquid supply pipes 31a and 31b into the inlet pipes 10a and 11a of the expanders 10 and 11 to heat the compressed air, the expanders 10 and 11 and the compressed air can be heated in a short time, thereby improving the start-up characteristics when the expanders are started. As a result, the low-temperature operating time of the expanders 10 and 11 immediately after the discharge operation is shortened, and they can quickly transition to higher temperature conditions for greater efficiency, thus improving the system efficiency (power recovery efficiency) of the CAES device 1-1. In addition, as mentioned above, the time required to reach a temperature suitable for power generation is shortened, which also improves responsiveness to fluctuations in power demand.
[0045] In addition, in the CAES apparatus 1-1 of the above-described embodiment 1, as shown in Figure 3, a jet-type nozzle 50 may be provided at the joint between the liquid supply pipe 31a and the inlet pipe 10a, and the high-temperature water in the liquid supply pipe 31a may be sprayed into the compressed air of the inlet pipe 10a using this nozzle 50.
[0046] By spraying with this nozzle 50, high-temperature water is uniformly mixed into the compressed air, making it less likely for uneven heating to occur due to water distribution, and the compressed air can be heated efficiently in a short time. This further improves the start-up characteristics and power generation efficiency when the expander is started. In addition, since the high-temperature water is uniformly mixed into the compressed air before it flows into the expander 10, this water diffuses into the expander 10 together with the compressed air, further improving the sealing and lubrication of the expander. Similarly, a nozzle 50 can also be provided at the joint between the supply pipe 31b and the inlet pipe 11a.
[0047] Furthermore, as the expanders 10 and 11 of Example 1, an expander having a structure in which the expansion mechanism 101 of expander 10 in Figure 2 is inverted can also be used. In this expander, as shown in Figure 4, high-temperature water is injected from the liquid supply pipe 31a connected to the upper part of the inlet pipe 10a and mixed with the compressed air flowing through the inlet pipe 10a. This water, together with the compressed air, flows into the casing bore 104 through the suction passage 113 at the top of the main casing 102 and is discharged from the discharge port 112. In this expander, since the discharge port 112 is located at the bottom of the main casing 102, the effect of easily discharging water to the outside can be obtained.
[0048] In the case of this expansion machine as well, it is preferable to provide a nozzle 50 at the joint between the liquid supply pipe 31a and the inlet pipe 10a, and to supply high-temperature water by spraying it.
[0049] Example 2 Figure 5 shows a schematic configuration diagram of CAES apparatus 1-2 according to Embodiment 2 of the present invention. Hereafter, the same reference numerals are used for components similar to those in Embodiment 1, and redundant explanations are omitted. In this CAES apparatus 1-2, instead of connecting the liquid supply pipes 31a and 31b of CAES apparatus 1-1 of Embodiment 1 to the inlet pipes 10a and 11a, which are the air inlets of the expanders 10 and 11, the liquid supply passages 60 formed in the main casing of the expanders 10 and 11 and for directly injecting high-temperature water from the first tank 21 into the working chambers of the expanders 10 and 11, are connected. Here, we will describe the case in which the expanders 10 and 11 shown in Figure 4 (with a structure in which compressed air flows in from the top of the casing and is discharged downwards) are used as the expanders 10 and 11.
[0050] As shown in Figure 6, the above-described liquid supply passage 60 is formed in the upper part of the main casing 102 of the expander, connecting the outside of the main casing 102 to the internal casing bore 104 in a vertical direction. One end of the liquid supply passage 60 opens to a position facing the working chamber formed inside the main casing 102 during the expansion stroke, and a nozzle 50 is provided at this opening. A liquid supply pipe 31a is connected to the other end of the liquid supply passage 60 that opens to the outside of the main casing 102, and the system is configured to supply high-temperature water from the accumulator tank 8 from the liquid supply pipe 31a to the liquid supply passage 60.
[0051] Figure 7 shows a cross-sectional view AA of the expander in Figure 6. The main casing 102 has a male rotor 106 and a female rotor 107 arranged to mesh with each other. The rotation shaft 115 of the male rotor 106 is rotatably supported by bearings 115a and 115b, and the rotation shaft 116 of the female rotor 107 is rotatably supported by bearings 116a and 116b.
[0052] Furthermore, the liquid supply passages 60 are formed in two locations corresponding to the male rotor 106 and female rotor 107, and the liquid supply piping 31a is branched into two at the end that connects to the liquid supply passages 60 and connected to each liquid supply passage 60.
[0053] In this expander, during discharge operation, compressed air from the accumulator tank 8 is drawn into the main casing 102 through the inlet pipe 10a and suction passage 113, and into the space (operating chamber) formed inside the main casing 102, which is surrounded by the casing bore 104, male rotor 106, and female rotor 107. This compressed air expands in the operating chamber, which gradually increases in volume as it rotates, causing the male rotor 106 and female rotor 107 to rotate, and the generator 12 connected to the rotation shaft 115 of the male rotor 106 to rotate and generate electricity. The air after the expansion stroke is discharged through the discharge port 112.
[0054] In this embodiment 2, as in embodiment 1, the water is pressurized by the liquid supply pump 30 and maintained at a higher pressure than the air stored in the pressure storage tank 8. During the discharge operation described above, the transfer pump 28 of the heat storage unit 1C is activated, and the high-temperature water from the first tank 21 is supplied from the liquid supply pipe 31a to the liquid supply passage 60.
[0055] Here, the liquid supply passage 60 is positioned to open directly into the working chamber, which is in the expansion stroke after the compressed air has finished flowing in, thus communicating with the working chamber. At this time, the working chamber is already in the expansion stroke and its pressure is slightly lower than the inlet air pressure, so the pressure difference allows high-temperature water to flow into the working chamber from the liquid supply passage 60. As a result, high-temperature water is sprayed into the working chamber via the nozzle 50. This sprayed high-temperature water mixes with the air in the expansion stroke, heats the air, and is discharged from the discharge port 112 along with the air after the expansion stroke.
[0056] Next, we will explain the effect of spraying high-temperature water into the working chamber. After the compressed air that flows into the working chamber of the expander is fully drawn in, it increases in volume due to adiabatic expansion, depressurizes, and cools down. This change during the expansion process is basically an adiabatic change in which there is no heat exchange with the air. However, by spraying high-temperature water into the working chamber from the nozzle of the liquid supply passage 60, heat is transferred from the high-temperature water to the air, and the temperature drop of the air can be kept to a minimum.
[0057] Therefore, the expansion stroke approaches an isothermal change with a larger volume change, rather than an adiabatic change, allowing for greater expansion work to be obtained. This air heating effect improves the overall adiabatic efficiency of the expander, increasing the shaft output that powers the generator. As a result, the amount of electricity generated increases.
[0058] Furthermore, when high-temperature water is sprayed into the working chamber, this water adheres to the surfaces of the casing bore 104, male rotor 106, and female rotor 107, sealing the gaps between them. As a result, air leakage between the working chambers is reduced, increasing volumetric efficiency, which in turn increases the shaft output of the expander and further improves the overall adiabatic efficiency.
[0059] As described above, in this embodiment 2, by directly spraying high-temperature water into the working chambers of the expanders 10 and 11 to heat the air inside the working chambers, the expansion stroke of the compressed air in the expander can be brought closer to an isothermal change, thereby improving the overall adiabatic efficiency of the expander. Therefore, it is possible to realize an expander with increased output and increased power generation.
[0060] Furthermore, in addition to the method of raising the temperature of the air flowing into the expanders 10 and 11 using heat exchangers 26 and 27, the air temperature is also raised by directly spraying high-temperature water. This allows for a rapid temperature rise, enabling a quick transition to high-efficiency operating conditions even during non-steady-state operation such as startup. As a result, it is possible to provide a CAES device with improved power generation and power generation efficiency, and an overall improved system efficiency (power recovery efficiency).
[0061] In this embodiment 2, the axial direction of the liquid supply passage 60 is provided so as to be approximately perpendicular to the surface in contact with the casing bore 104. However, the axial direction of the liquid supply passage 60 does not necessarily have to be perpendicular to the surface in contact with the casing bore 104, and the axial direction of the liquid supply passage 60 may be inclined at an angle to the surface in contact with the casing bore 104. Furthermore, the nozzle 50 may be an integral structure with the main casing 102 or it may be made from a separate component.
[0062] Furthermore, in this embodiment 2, the liquid supply passage 60 is positioned at an opening that directly communicates with the working chamber during the expansion stroke. However, this opening can also be positioned near the suction port 111. In this case, although the pressure difference for spraying cannot be increased, the air can be heated before the expansion stroke begins. Also, although two liquid supply passages 60 are provided to spray high-temperature water onto the male rotor 106 and female rotor 107, one may be provided at the position where the male and female rotors 106 and 107 mesh. In this case, only one liquid supply passage 60 and one nozzle 50 need to be installed, thus reducing the necessary manufacturing work.
[0063] Furthermore, while a jet-type nozzle 50 was used in the above-described examples 1 and 2, a collision-type nozzle with multiple nozzle holes can also be used instead to obtain a spray stream with smaller particle sizes. As the particle size of the spray stream decreases, the surface area for heat exchange increases, thus promoting heat exchange and enhancing the temperature rise effect.
[0064] Example 3 Figure 8 shows a schematic configuration diagram of CAES apparatus 1-3 according to Embodiment 3 of the present invention. CAES apparatus 1-3 of Embodiment 3 uses a single-stage compression and single-stage expansion system instead of the multi-stage compression and multi-stage expansion system of CAES apparatus 1-1 of Embodiment 1. That is, the compressor unit 3A of this CAES apparatus 1-3 has one motor 4, a compressor 6 and a pressure accumulator tank 8, and the expander unit 3B has one expander 10 and a generator 12.
[0065] Furthermore, the heat storage unit 3A includes a high-temperature first tank 21 and a low-temperature second tank 22 for storing water, which is a liquid heat storage medium; a heat exchanger 24 for exchanging heat between the air discharged from the compressor 6 and the water in the second tank 22; and a heat exchanger 26 for exchanging heat between the compressed air just before it flows into the expander 10 and the water in the first tank 21.
[0066] Furthermore, this CAES device 1-3, like the CAES device 1-1 of Example 1, is equipped with a liquid supply pipe 31a for supplying high-temperature water stored in the first tank to the inlet pipe 10a of the expander 10, and a flow control valve 33a for adjusting the flow rate of this liquid supply pipe 31a. Therefore, the performance (sealing and lubricity) of the expander 10 can be improved, thereby increasing power generation efficiency.
[0067] In this CAES apparatus 1-3, although the temperature of the heat-exchanging air is higher compared to a two-stage compression and two-stage expansion system, the system configuration is simplified, making it easier to construct a CAES apparatus.
[0068] As described above, the CAES devices 1-3 of this embodiment 3 allow for the manufacture of a CAES device with improved system efficiency (power recovery efficiency) in a simpler configuration and at a lower cost.
[0069] Furthermore, in this embodiment 3, the CAES devices 1-3 can be configured using existing compressors already in use in factories, etc., thereby improving the efficiency of the expander and the system efficiency of the CAES device.
[0070] Example 4 Figure 9 shows a schematic configuration diagram of CAES apparatus 1-4 according to Embodiment 4 of the present invention. CAES apparatus 1-4 of Embodiment 4 is a CAES apparatus 1-3 of Embodiment 3, which has a single-stage compression and single-stage expansion system, with the addition of a gas-liquid separator 70 connected to the discharge port of the expander 10. The gas-liquid separator 70 releases the air, which is the gas discharged from the discharge port of the expander 10, into the atmosphere. On the other hand, the water, which is the liquid, is returned to the liquid supply pump 30 via the recovery pipe 71 and supplied again to the second tank 22 on the low-temperature side by the liquid supply pump 30.
[0071] By using the gas-liquid separator 70 in this way, water, which is a liquid heat storage medium, can be circulated and reused within the system without being released outside the system. Therefore, there is no need to separately replenish the water supplied to the expander inlet air in order to improve expansion power generation.
[0072] As described above, in this embodiment 4, the cost of supplying the heat storage medium during system operation does not increase, and system operating costs can be kept lower, while the efficiency of the expander and the system efficiency (power recovery efficiency) of the CAES device can be improved.
[0073] Furthermore, even in the CAES devices 1-1 and 1-2 of Embodiments 1 and 2, which have multi-stage compression and multi-stage expansion systems, it is useful to provide the gas-liquid separator 70 of Embodiment 4.
[0074] Example 5 Figure 10 shows a schematic configuration diagram of CAES apparatus 1-5 according to Embodiment 5 of the present invention. CAES apparatus 1-5 of Embodiment 5 is a CAES apparatus 1-3 of Embodiment 3, which has a single-stage compression and single-stage expansion system, with the addition of a pressure supply pipe 80 for pressurizing the water in the circuit of the heat storage unit 5C with high-pressure compressed air from the pressure storage tank 8.
[0075] Since the air flowing into the inlet pipe 10a of the expander 10 is high-pressure compressed air flowing in from the accumulator tank 8, the high-temperature water supplied to the inlet pipe 10a of the expander 10 by the liquid supply pipe 31a must be at a pressure equal to or greater than the high-pressure compressed air from the accumulator tank 8 in order to be supplied to the expander inlet air. Therefore, in the CAES device 1-5 of this embodiment 5, a pressure supply pipe 80 is provided, which branches off the air supply pipe 17 for supplying compressed air from the accumulator tank 8 to the expander 10 and connects to the second tank 22 of the heat storage unit 5C. This pressure supply pipe 80 introduces the high-pressure compressed air from the accumulator tank 8 into the low-temperature second tank 22, and this compressed air is used to pressurize the water circulating within the circuit of the heat storage unit 5C.
[0076] In this embodiment 5, the water, which is the liquid heat storage medium, is always pressurized to the same pressure as the inlet air of the expander 10. Therefore, high-temperature water from the first tank 21 can be supplied to the expander inlet from the liquid supply pipe 31a without being obstructed by the high-pressure compressed air at the expander inlet. Alternatively, the pressure supply pipe 80 may be connected to the first tank 21 of the heat storage unit 5C, and the high-pressure compressed air from the pressure storage tank 8 may be introduced into the high-temperature side of the first tank 21.
[0077] As described above, in this embodiment 5, the water pressure in the heat storage unit 5C during system operation can be easily made equal to the pressure in the storage tank 8. Therefore, there is no need to adjust the pressure by the liquid supply pump 30, and the efficiency of the expander and the system efficiency (power recovery efficiency) of the CAES device can be improved with a simple configuration.
[0078] Furthermore, in the CAES devices of Examples 3 to 5 described above (single-stage compression / single-stage expansion systems), instead of connecting the liquid supply pipe 31a to the inlet pipe 10a, as in CAES device 1-2 of Example 2, the liquid supply pipe 31a can be connected to the liquid supply passage 60 formed in the main casing of the expander 10, thereby directly supplying the high-temperature water from the first tank 21 to the working chamber of the expander 10.
[0079] Furthermore, even in the CAES devices 1-1 and 1-2 of Embodiments 1 and 2, which have multi-stage compression and multi-stage expansion systems, it is useful to provide the pressure supply piping 80 of Embodiment 5.
[0080] ≪Example 6≫ Figure 11 shows a schematic configuration diagram of CAES apparatus 1-6 according to Embodiment 6 of the present invention. CAES apparatus 1-6 of Embodiment 6 is configured in the same way as CAES apparatus 1-1 of Embodiment 1, in which water from the second tank 22 on the low-temperature side is supplied to the compressors 6 and 7 during the compression stroke to increase the compression efficiency of the compressors 6 and 7.
[0081] In addition, the CAES apparatuses of the above-described embodiments 1 to 5 may also be configured to supply water from the second tank 22 on the low-temperature side to the compressors 6 and 7 during the compression stroke to improve compression efficiency.
[0082] Example 7 Figure 12 shows a schematic configuration diagram of LAES apparatus 2-1 according to Embodiment 7 of the present invention. Similar to CAES apparatus 1-1 of Embodiment 1, LAES apparatus 2-1 of Embodiment 7 is an LAES apparatus in which the liquid supply pipes 31a and 31b are connected to the inlet pipes 10a and 11a, which are the air inlets of the expanders 10 and 11. The following will only describe the differences in configuration from Example 1.
[0083] In the compressor unit 7A, the discharge port of the compressor 7 is connected to the accumulator tank 48 via a heat exchanger 40 and a pressure reducing valve 41, in addition to the heat exchanger 25. The air compressed by the compressor 7 undergoes heat exchange through the heat exchanger 25 of the heat storage unit 7C and then flows into the heat exchanger 40. The air that flows into the heat exchanger 40 exchanges heat with cold and is liquefied, then further expands and cools in the pressure reducing valve 41, and is then stored in the accumulator tank 48.
[0084] The inlet pipe 10a, which is the air inlet for the first stage expander 10 of the expander unit 7B, is connected to the heat exchanger 40 of the compressor unit 7A via the heat exchanger 26 and on-off valve 15 of the heat storage unit 7C, and further connected to the pressure storage tank 48. During the expansion stroke (discharge operation), the on-off valve 15 and the pressure reducing valve 43 are opened, and the liquid air stored in the pressure storage tank 48 exchanges heat with the heat storage medium in the heat exchanger 40. The heat-exchanged liquid air is configured to rise in temperature to about room temperature and vaporize, and then be supplied to the expander 10 through the heat exchanger 26.
[0085] Next, the charging and discharging operations of the LAES device 2-1 will be described. The following describes only the differences in operation compared to Example 1.
[0086] (during charging operation) Air compressed in two stages by compressors 6 and 7 flows into heat exchanger 40 via heat exchanger 25. In heat exchanger 40, the incoming compressed air is cooled to approximately -160°C and liquefied by heat exchange with the already cooled heat storage medium inside heat exchanger 40. The liquefied air passes through pressure reducing valve 41, is further reduced in pressure and cooled, and then stored in pressure accumulator 48. In pressure accumulator 48, the reduced-pressure air separates into gas and liquid by pressure reducing valve 41. The gaseous air passes through pressure reducing valve 45, returns to heat exchanger 40, exchanges heat with the incoming compressed air to cool it, and then returns to the inlet of compressor 7, where it is compressed again. The liquid air is stored in pressure accumulator 48 at a pressure of approximately 1.5 to 2 MPa.
[0087] (During discharge operation) The stored liquid air is transferred by the transfer pump 42 from the pressure accumulator tank 48 through the pressure reducing valve 43 into the heat exchanger 40. In the heat exchanger 40, the liquid air exchanges heat with the heat storage medium inside the heat exchanger 40, and after its temperature rises to approximately room temperature and it vaporizes, it flows through the on-off valve 15 and the heat exchanger 26 into the inlet pipe 10a of the expander 10, where it undergoes adiabatic expansion (first stage) to drive the expander 10.
[0088] The subsequent operation is the same as that of CAES device 1-1 in Example 1. Similar to CAES device 1-1 in Example 1, it is possible to construct an LAES device that has improved power generation efficiency and improved responsiveness to fluctuations in power demand. Furthermore, with an LAES device, the tank capacity for air storage and the installation space can be significantly reduced compared to a CAES device, allowing for the construction of a device with fewer installation constraints and further cost reduction.
[0089] In the above-described Examples 2 to 6, the LAES apparatus (2-2 to 2-6) can also be configured by storing compressed air as liquid air using the heat exchanger 40 (Examples 8 to 12 shown in Figures 13 to 17).
[0090] Furthermore, in each of the embodiments described above, the renewable energy sources used for power generation can include all forms of energy that are replenished steadily (or repeatedly) by natural forces and fluctuate irregularly, such as wind power, solar power, solar thermal energy, wave power or tidal power, flowing water or tides, and geothermal energy. The power may also fluctuate due to other high-power-consuming equipment within the factory. Moreover, the grid power supplying this electricity may not be grid power, but rather regional or factory-specific microgrid power.
[0091] Furthermore, in each of the embodiments described above, the compressors 6 and 7 and the expanders 10 and 11 are screw type, but their type is not limited, and compressors and expanders of the scroll type, turbo type, and reciprocating type can be used.
[0092] Furthermore, while the CAES or LAES devices in Examples 1, 2, 6, 7, 8, and 12 described above use a two-stage compression and two-stage expansion type with compressors 6 and 7 and expanders 10 and 11, it is also applicable to three or more stages, and even combinations of different numbers of stages for compression and expansion. In addition, while the CAES or LAES devices in Examples 3-5 and 9-11 described above use one compressor and one expander, the number is not particularly limited, and there may be two or more units. Also, the number of motors and compressors, and the number of generators and expanders may be different combinations.
[0093] Furthermore, although the compressors 6 and 7 and the expanders 10 and 11 are separate devices in each of the embodiments described above, the compressor and expander (motor and generator) may be combined into one unit.
[0094] Furthermore, in each of the above embodiments, water (pressurized water) is used as the liquid heat storage medium. Compared to other heat storage mediums such as silicone oil and synthetic oil, water has a large specific heat (heat capacity), making it a suitable material for heat storage, and it also has high thermal conductivity, making it easy to transfer heat. In addition, in each of the above embodiments, liquid heat storage mediums other than water, such as oil, can also be used, but oil-based heat storage mediums have high viscosity at low temperatures, which increases the pump power required for transfer, whereas water has low viscosity even at low temperatures and excellent transport characteristics, making it preferable.
[0095] However, since water vaporizes at 100°C at normal pressure (atmospheric pressure), it is preferable to use it under pressure to store heat at temperatures above 100°C. For example, pressurizing it to 1 MPa will keep it in the liquid phase up to approximately 180°C.
[0096] In addition, in the present invention, instead of using the liquid supply piping and pump shown in each of the above embodiments, a configuration may be used in which a portion of the high-temperature water (liquid heat storage medium) stored in the first tank 21 is taken out, and this water is pressurized to a pressure higher than the pressure of the compressed air flowing into the expander and injected directly into the expander. [Explanation of symbols]
[0097] 1-1~1-6 CAES device 2-1~2-6 LAES device 1A~12A Compressor Unit 1B~12B Expansion Unit 1C~12C Heat Storage Unit 4.5 Motor 6,7 Compressor 8,48 Pressure tank 10,11 Inflator 10a, 11a Inlet piping 12,13 Generators 14 Power Conditioner 17. Air supply piping 20 Grid Power 21 Tank No. 1 22 Tank No. 2 24~27,40 Heat exchanger 28, 29, 42 Transfer pumps 30 Liquid supply pump 31, 31a, 31b Liquid supply piping 32a, 32b Liquid supply branch piping 33a,33b Flow rate adjustment valve 41, 43, 45 Pressure Reducing Valve 50 nozzles 60 Liquid supply passage 70 Gas-liquid separator 80 Pressure supply piping 101 Expansion mechanism 102 Casing 104 Casing Bore 106 Male rotor 107 Female Rotor 111 Inlet 112 Discharge port 113 Intake passage 115a, 115b bearings 116a, 116b bearings
Claims
1. A compressor that compresses air, A liquid supply pump for supplying a liquid medium, A first heat exchanger that exchanges heat between air compressed by the compressor and a liquid medium supplied by the supply pump, A pressure storage tank for storing the air after heat exchange in the first heat exchanger, A heat storage tank for storing the liquid medium after heat exchange in the first heat exchanger, A second heat exchanger that exchanges heat between the air stored in the pressure storage tank and the liquid medium stored in the heat storage tank, An expander driven by the air whose heat has been exchanged in the second heat exchanger, A supply piping is connected to the pressure accumulator and the expander via the second heat exchanger, and supplies air supplied from the pressure accumulator to the expander. A liquid supply piping is connected to the liquid supply pump and the expansion machine via the first heat exchanger and the heat storage tank, and supplies the liquid medium supplied from the liquid supply pump to the expansion machine. An energy storage device characterized by comprising the following features.
2. In the energy storage device according to claim 1, A liquid supply branch pipe that branches off from the aforementioned liquid supply pipe and supplies the liquid medium supplied from the heat storage tank to the second heat exchanger, An energy storage device characterized by comprising the following features.
3. In the energy storage device according to claim 1, The liquid supply pump pressurizes the liquid medium supplied from the heat storage tank to the liquid supply piping so that it has a pressure greater than or equal to the pressure of the air stored in the pressure storage tank. An energy storage device characterized by the following features.
4. In the energy storage device according to claim 1, The aforementioned liquid supply piping is connected to the air inlet of the expander. An energy storage device characterized by the following features.
5. In the energy storage device according to claim 1, The expansion unit has a liquid supply passage formed to connect the inside and outside of its casing, and the liquid supply piping is connected to the liquid supply passage of the expansion unit. An energy storage device characterized by the following features.
6. In the energy storage device according to claim 1, The liquid supply piping has a nozzle for spraying the liquid medium onto the expander. An energy storage device characterized by the following features.
7. In the energy storage device according to claim 1, The system includes a gas-liquid separator connected to the discharge port of the aforementioned expander, which recovers the air and liquid medium discharged from the expander and separates them into gas and liquid components. The liquid medium separated by the gas-liquid separator is supplied again to the first heat exchanger. An energy storage device characterized by the following features.
8. In the energy storage device according to claim 1, The system includes a pressure supply pipe that branches off from the aforementioned air supply pipe and connects the pressure accumulator and the heat storage tank. An energy storage device characterized by the following features.
9. In the energy storage device according to claim 1, Water is used as the liquid medium. An energy storage device characterized by the following features.
10. In the energy storage device according to claim 1, The compressor is composed of a single-stage compressor and a two-stage compressor. The first heat exchanger is provided on the discharge side of the first-stage compressor and the second-stage compressor, respectively. The aforementioned expansion machine is composed of a single-stage expansion machine and a double-stage expansion machine. The second heat exchanger is provided on the inlet side of the first-stage expander and the second-stage expander, respectively. An energy storage device characterized by the following features.
11. In the energy storage device according to claim 1, The system includes a third heat exchanger that cools the air after heat exchange in the first heat exchanger and heats the air stored in the pressure accumulator. An energy storage device characterized by the following features.
12. Screw rotor and, The casing has a cylindrical casing bore in which the screw rotor is rotatably housed, and a fluid supply passage is formed in the casing bore so as to communicate the working chamber formed therein with the outside, When working fluid flows into the working chamber of the casing bore and the screw rotor is rotated by the expansion of the working fluid, a liquid medium having a temperature higher than the temperature of the working fluid is injected into the working chamber of the casing bore from the fluid supply passage of the casing. A screw-type inflator characterized by the following features.