Compressed air energy storage device

Abstract

Provided is a compressed air energy storage device for achieving improved efficiency in the generation and storage of compressed air.　The compressed air energy storage device comprises: a low pressure tank 15 and a high pressure tank 17 that store compressed air; a pneumatic apparatus 16 driven by the compressed air of the low pressure tank 15; generators 19A, 19B driven by expanders 18A, 18B driven by the compressed air of the high pressure tank 17; a switching valve 20 that switches the supply destination of the compressed air from compressors 12A, 12B driven by electric motors 11A, 11B between the low pressure tank 15 and the high pressure tank 17; and a control device 30. The control device 30 controls the rotation speeds of the electric motors 11A, 11B so that the pressure of the low-pressure tank 15 becomes a first target value when the supply destination of the compressed air is the low-pressure tank 15, and controls the rotation speeds of the electric motors 11A, 11B so that the pressure of the high-pressure tank 17 becomes a second target value when the supply destination of the compressed air is the high-pressure tank 17.

Description

Compressed Air Energy Storage Device

[0001] The present invention relates to a compressed air energy storage device.

[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. In order to smooth the power generation output against such fluctuations, a compressed air energy storage device has been proposed (see, for example, Patent Document 1). The compressed air energy storage device stores electrical energy as compressed air in a storage tank, and when power is required, the expansion machine is driven by the compressed air to operate the generator, generating electrical energy and smoothing the output.

[0003] Japanese Patent No. 6649141

[0004] When a compressed air energy storage device is adopted in a factory or the like that uses pneumatic equipment driven by compressed air, due to the balance between the use for pneumatic equipment and the use for the expansion machine, it is desirable to improve the efficiency of generating and storing compressed air. One of the problems of the present invention is to improve the efficiency of generating and storing compressed air.

[0005] To solve the above problems, the configuration described in the claims is applied. The present invention includes a plurality of means for solving the above problems, but to give one example, the compressed air energy storage device includes an electric motor, a compressor driven by the electric motor to generate compressed air, a low-pressure tank for storing the compressed air generated by the compressor, a pneumatic device driven by the compressed air stored in the low-pressure tank, a high-pressure tank for storing the compressed air generated by the compressor, an expander driven by the compressed air stored in the high-pressure tank, a generator driven by the expander, a first switching valve for switching the supply destination of compressed air from the compressor between the low-pressure tank and the high-pressure tank, a first pressure sensor for detecting the pressure of the low-pressure tank, and the pressure of the high-pressure tank The system includes a second pressure sensor for detection, an inverter for controlling the rotational speed of the electric motor, and a control device for controlling the first switching valve and the inverter. When the control device controls the first switching valve to direct the supply of compressed air from the compressor to the low-pressure tank, it controls the rotational speed of the electric motor via the inverter so that the pressure detected by the first pressure sensor becomes a preset first target value. When the control device controls the first switching valve to direct the supply of compressed air from the compressor to the high-pressure tank, it controls the rotational speed of the electric motor via the inverter so that the pressure detected by the second pressure sensor becomes a preset second target value higher than the first target value.

[0006] According to the present invention, it is possible to improve the efficiency of generating and storing compressed air.

[0007] Furthermore, other issues, structures, and effects not mentioned above will be clarified in the following explanation.

[0008] This is a schematic diagram showing the configuration of a compressed air energy storage device in one embodiment of the present invention. This is a block diagram showing the control device together with related equipment in one embodiment of the present invention.

[0009] One embodiment of the present invention will be described with reference to the drawings.

[0010] Figure 1 is a schematic diagram showing the configuration of the compressed air energy storage device in this embodiment. Figure 2 is a block diagram showing the control device in this embodiment together with related equipment.

[0011] The compressed air energy storage device of this embodiment comprises, as equipment constituting the compressed air generation unit, electric motors 11A and 11B, a compressor 12A driven by the electric motor 11A to compress air, a heat exchanger 13A (first heat exchanger) that cools the compressed air discharged from the compressor 12A by heat exchange with a heat transfer medium, a cooler 14A that further cools the compressed air cooled by the heat exchanger 13A, a compressor 12B driven by the electric motor 11B to further compress the compressed air cooled by the cooler 14A, a heat exchanger 13B (first heat exchanger) that cools the compressed air discharged from the compressor 12B by heat exchange with a heat transfer medium, and a cooler 14B that further cools the compressed air cooled by the heat exchanger 13B.

[0012] The compressed air energy storage device of this embodiment includes a low-pressure tank 15 for storing compressed air generated by the compressed air generation unit (i.e., compressors 12A, 12B) described above, a pneumatic device 16 driven by the compressed air stored in the low-pressure tank 15, a high-pressure tank 17 for storing compressed air generated by the compressed air generation unit, expanders 18A, 18B mainly driven by the compressed air stored in the high-pressure tank 17, generators 19A, 19B driven by the expanders 18A, 18B, and a switching valve 20 (first switching valve) for switching the supply destination of compressed air from the compressed air generation unit between the low-pressure tank 15 and the high-pressure tank 17.

[0013] The switching valve 20 is, for example, a three-way valve that switches between a state in which the inlet side (i.e., the compressed air generation unit) is connected to one outlet side (i.e., the low-pressure tank 15) and a state in which the inlet side (i.e., the compressed air generation unit) is connected to the other outlet side (i.e., the high-pressure tank 17).

[0014] The compressed air energy storage device of this embodiment includes a switching valve 21 (second switching valve) that switches the supply of compressed air from the high-pressure tank 17 to the expanders 18A and 18B on and off, and a switching valve 22 (third switching valve) that switches the destination of the compressed air supplied from the low-pressure tank 15 between the pneumatic equipment 16 and the expanders 18A and 18B.

[0015] The switching valve 21 is, for example, a three-way valve that switches between a state in which one inlet side (i.e., the high-pressure tank 17) is connected to the outlet side (i.e., the expanders 18A and 18B) and a state in which the other inlet side is connected to the outlet side (i.e., the expanders 18A and 18B). The switching valve 22 is, for example, a three-way valve that switches between a state in which the inlet side (i.e., the low-pressure tank 15) is connected to one outlet side (i.e., the pneumatic equipment 16) and a state in which the inlet side (i.e., the low-pressure tank 15) is connected to the other outlet side. The other inlet side of the switching valve 21 and the other outlet side of the switching valve 22 are connected to each other. Depending on the state of the switching valves 21 and 22, compressed air is supplied from the high-pressure tank 17 or the low-pressure tank 15 to the expanders 18A and 18B, or the supply of compressed air to the expanders 18A and 18B is stopped.

[0016] The compressed air energy storage device of this embodiment includes a heat transfer tank 23A for storing a low-temperature heat transfer medium, a pump 24A for supplying the heat transfer medium stored in the heat transfer tank 23A to heat exchangers 13A and 13B, a heat transfer tank 23B for storing a high-temperature heat transfer medium heated by the heat exchangers 13A and 13B, and heat exchangers 25A and 25B (second) for heating the compressed air supplied to the expanders 18A and 18B through heat exchange with the heat transfer medium stored in the heat transfer tank 23B. The system includes a third heat exchanger (a heat exchanger) that generates hot water by heating water through heat exchange with a heat transfer medium stored in a heat transfer medium tank 23B, a fourth switching valve (a switching valve) that switches the supply destination of the heat transfer medium stored in the heat transfer medium tank 23B between the heat exchangers 25A, 25B and the heat exchanger 26, and a pump 24B that supplies the heat transfer medium stored in the heat transfer medium tank 23B to the heat exchangers 25A, 25B or the heat exchanger 26 via the switching valve 27. The heat transfer medium cooled in the heat exchangers 25A, 25B or the heat exchanger 26 is returned to the heat transfer medium tank 23A.

[0017] The compressed air energy storage device of this embodiment includes a pressure sensor 28 (first pressure sensor) for detecting the pressure in a low-pressure tank 15, a pressure sensor 29 (second pressure sensor) for detecting the pressure in a high-pressure tank 17, inverters 30A and 30B for controlling the rotational speeds of electric motors 11A and 11B respectively, and a control device 31 for controlling the switching valves 20-22, 27 and inverters 30A and 30B. The control device 31 includes a processor that executes control according to a program, and a memory for storing programs and data.

[0018] The control device 31 controls the switching valve 20 and inverters 30A and 30B based on the detection results of the pressure sensors 28 and 29. More specifically, the control device 31 stores a first target value (e.g., 0.7 MPa) set in advance for the pressure of the low-pressure tank 15, an upper limit value (e.g., 0.8 MPa) set in advance higher than the first target value, a lower limit value (e.g., 0.6 MPa) set in advance lower than the first target value, and a second target value (e.g., 1.2 MPa) set in advance higher than the first target value for the pressure of the high-pressure tank 17.

[0019] The control device 31 initially controls the switching valve 20 to direct the supply of compressed air from the compressed air generation unit to the low-pressure tank 15. The control device 31 also controls the rotational speed of the electric motors 11A and 11B via inverters 30A and 30B so that the pressure detected by the pressure sensor 28 reaches a first target value. As a result, compressed air is supplied from the compressed air generation unit to the low-pressure tank 15 for storage.

[0020] As compressed air is supplied from the compressed air generation unit to the low-pressure tank 15, if the pressure detected by the pressure sensor 28 rises to the upper limit, the control device 31 controls the switching valve 20 to switch the destination of the compressed air supply from the compressed air generation unit to the high-pressure tank 17. The control device 31 also controls the rotational speed of the electric motors 11A and 11B via inverters 30A and 30B so that the pressure detected by the pressure sensor 29 reaches a second target value. As a result, compressed air is supplied from the compressed air generation unit to the high-pressure tank 17 and stored there.

[0021] As compressed air is supplied from the compressed air generation unit to the high-pressure tank 17, if the pressure detected by the pressure sensor 28 drops to a lower limit, the control device 31 controls the switching valve 20 to switch the destination of the compressed air supply from the compressed air generation unit to the low-pressure tank 15. The control device 31 also controls the rotational speed of the electric motors 11A and 11B via inverters 30A and 30B so that the pressure detected by the pressure sensor 28 reaches a first target value. As a result, compressed air is supplied from the compressed air generation unit to the low-pressure tank 15 for storage.

[0022] The control device 31 controls the switching valves 21, 22, and 27 in response to the operation of the mode switch 32 or an external command. More specifically, for example, if the first mode, which uses compressed air only for the pneumatic equipment 16, is selected by the mode switch 32, the control device 31 controls the switching valve 22 to supply compressed air from the low-pressure tank 15 to the pneumatic equipment 16, and controls the switching valve 21 to stop the supply of compressed air from the high-pressure tank 17 to the expanders 18A and 18B. The control device 31 also controls the switching valve 27 to supply the heat transfer medium stored in the heat transfer medium tank 23B to the heat exchanger 26. The temperature and volume of the heat transfer medium stored in the heat transfer medium tank 23B are detected by a sensor (not shown), and the control device 31 may control the pump 24B so that the supply and cessation of the heat transfer medium to the heat exchanger 26 are switched based on these values.

[0023] For example, when the second mode, which uses compressed air for the pneumatic equipment 16 and expanders 18A and 18B, is selected by the mode switch 32, the control device 31 controls the switching valve 22 to supply compressed air from the low-pressure tank 15 to the pneumatic equipment 16 and controls the switching valve 21 to supply compressed air from the high-pressure tank 17 to the expanders 18A and 18B. The control device 31 also controls the switching valve 27 to supply the heat transfer medium stored in the heat transfer medium tank 23B to the heat exchangers 25A and 25B.

[0024] For example, if a third mode is selected by the mode switch 32, in which compressed air is used only for expanders 18A and 18B, the control device 31 controls the switching valve 27 to supply the heat transfer medium stored in the heat transfer medium tank 23B to the heat exchangers 25A and 25B. The control device 31 also controls the switching valves 21 and 22 based on the detection results of the pressure sensors 28 and 29. More specifically, if the pressure detected by the pressure sensor 29 exceeds a threshold value (for example, 0.1 MPa) that has been set lower than a second target value, the control device 31 controls the switching valves 21 and 22 to set the source of compressed air to expanders 18A and 18B as the high-pressure tank 17. If the pressure detected by the pressure sensor 29 is below the threshold value and the pressure detected by the pressure sensor 28 exceeds the lower limit value, the control device 31 controls the switching valves 21 and 22 to set the source of compressed air to expanders 18A and 18B as the low-pressure tank 15.

[0025] As described above, the compressed air energy storage device of this embodiment includes a low-pressure tank 15 for storing compressed air mainly used in the pneumatic equipment 16, and a high-pressure tank 17 for storing compressed air used in the expanders 18A and 18B at a higher pressure than the low-pressure tank 15, thereby improving the efficiency of compressed air storage. In other words, the size of the tanks for storing compressed air can be reduced. Furthermore, by switching the supply destination of compressed air from the compressed air generation unit between the low-pressure tank 15 and the high-pressure tank 17, and by varying the rotational speed of the electric motors 11A and 11B via inverters 30A and 30B, the efficiency of compressed air generation can be improved.

[0026] In addition, although not specifically described in the above embodiment, the control device 31 may be controlled not to supply compressed air to the high-pressure tank 17 in response to an external command. More specifically, if compressed air is supplied from the compressed air generation unit to the low-pressure tank 15 and the pressure detected by the pressure sensor 28 rises to the upper limit, the control device 31 may stop the electric motors 11A and 11B. Subsequently, if the pressure detected by the pressure sensor 28 falls to the lower limit, the control device 31 may drive the electric motors 11A and 11B.

[0027] Furthermore, in the above embodiment, the compressed air energy storage device was described as being configured to switch the source of compressed air supply to the expanders 18A and 18B between the high-pressure tank 17 and the low-pressure tank 15. However, the device is not limited to this configuration, and may be configured to supply compressed air to the expanders 18A and 18B solely from the high-pressure tank 17.

[0028] Furthermore, although the above embodiment described an example in which the compressed air energy storage device is equipped with two compressors 12A and 12B, it is not limited to this and may be equipped with only one compressor. Also, although the above embodiment described an example in which the compressed air energy storage device is equipped with two expanders 18A and 18B, it is not limited to this and may be equipped with only one expander.

[0029] 11A, 11B... Electric motor, 12A, 12B... Compressor, 13A, 13B... Heat exchanger (first heat exchanger), 15... Low-pressure tank, 16... Pneumatic equipment, 17... High-pressure tank, 18A, 18B... Expander, 19A, 19B... Generator, 20... Switching valve (first switching valve), 21... Switching valve (second switching valve), 22... Switching valve (third switching valve), 25A, 25B... Heat exchanger (second heat exchanger), 26... Heat exchanger (third heat exchanger), 27... Switching valve (fourth switching valve), 28... Pressure sensor (first pressure sensor), 29... Pressure sensor (second pressure sensor), 30A, 30B... Inverter, 31... Control device

Claims

1. The system comprises an electric motor, a compressor driven by the electric motor to generate compressed air, a low-pressure tank for storing the compressed air generated by the compressor, pneumatic equipment driven by the compressed air stored in the low-pressure tank, a high-pressure tank for storing the compressed air generated by the compressor, an expander driven by the compressed air stored in the high-pressure tank, a generator driven by the expander, a first switching valve for switching the supply destination of compressed air from the compressor between the low-pressure tank and the high-pressure tank, a first pressure sensor for detecting the pressure in the low-pressure tank, a second pressure sensor for detecting the pressure in the high-pressure tank, an inverter for controlling the rotational speed of the electric motor, and a control device for controlling the first switching valve and the inverter, wherein when the control device controls the first switching valve to supply compressed air from the compressor to the low-pressure tank, it controls the rotational speed of the electric motor via the inverter so that the pressure detected by the first pressure sensor becomes a preset first target value. A compressed air energy storage device characterized in that, when the first switching valve is controlled to direct the supply of compressed air from the compressor to the high-pressure tank, the rotational speed of the electric motor is controlled via the inverter so that the pressure detected by the second pressure sensor becomes a second target value which is set to be higher than the first target value in advance.

2. The compressed air energy storage device according to claim 1, wherein the control device controls the first switching valve to switch the destination of the compressed air supply from the compressor to the high-pressure tank when compressed air is supplied from the compressor to the low-pressure tank and the pressure detected by the first pressure sensor rises to an upper limit value set in advance higher than the first target value, and controls the first switching valve to switch the destination of the compressed air supply from the compressor to the low-pressure tank when compressed air is supplied from the compressor to the high-pressure tank and the pressure detected by the first pressure sensor falls to a lower limit value set in advance lower than the first target value.

3. A compressed air energy storage device according to claim 2, comprising: a second switching valve for switching the supply and cessation of compressed air from the high-pressure tank to the expander; and a third switching valve for switching the destination of compressed air supplied from the low-pressure tank between the pneumatic equipment and the expander, wherein the control device controls the second and third switching valves to make the high-pressure tank the source of compressed air supplied to the expander when the pressure detected by the second pressure sensor exceeds a threshold value set in advance to be lower than the second target value; and controls the second and third switching valves to make the low-pressure tank the source of compressed air supplied to the expander when the pressure detected by the second pressure sensor is less than or equal to the threshold value and the pressure detected by the first pressure sensor exceeds the lower limit value.

4. A compressed air energy storage device according to claim 1, characterized in that it comprises a first heat exchanger that heats a heat transfer medium by heat exchange with the compressed air generated by the compressor, and a second heat exchanger that heats the compressed air supplied to the expander by heat exchange with the heat transfer medium heated by the first heat exchanger.

5. A compressed air energy storage device according to claim 4, characterized in that it comprises a third heat exchanger that heats water by heat exchange with a heat transfer medium heated in the first heat exchanger, and a fourth switching valve controlled by the control device that switches the supply destination of the heat transfer medium between the second heat exchanger and the third heat exchanger.

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