Compressed Air Energy Storage Device

Abstract

To provide a compressed-air energy storage device which can improve power collection efficiency by efficiently collecting compressed heat.SOLUTION: A compressed-air energy storage device comprises: a compressor driven by an electric motor, and compressing air; a first heat exchanger for heating a heat accumulation medium by exchanging heat with compressed air which is compressed by the compressor; a pressure accumulation tank for storing the compressed air after being heat-exchanged by the first heat exchanger; an expander driven by the compressed air which is stored in the pressure accumulation tank; a power generator driven by the expander; a second heat exchanger for heating the compressed air flowing into the expander by exchanging heat with the heat accumulation medium which is heated by the first heat exchanger; and a heat pump device for absorbing heat from the heat accumulation medium which has been heat-exchanged by the second heat exchanger, and radiating heat to the compressed air for driving the expander.SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] The present invention provides Compressed Air Energy Storage Device Regarding. [Background technology]

[0002] Power generation using renewable energy sources such as wind and solar power depends on weather conditions, and as such, the amount of power generated can fluctuate and be unstable. Compressed Air Energy Storage (CAES) systems are known as systems that can address these fluctuations and level out power generation output. Compressed air energy storage devices (CAES devices) that use this CAES system store electrical energy as compressed air in a pressure storage tank, and when electricity is needed, the compressed air drives an expander to operate a generator, generating electrical energy and leveling out output.

[0003] To improve power generation efficiency, CAES systems are known that recover compression heat in a heat storage medium, store it in a heat storage tank, and use the recovered compression heat to heat compressed air before expansion. This reduces heat loss during storage in the storage tank and increases the power recovered during expansion. CAES systems require a high ratio of the output energy used to drive the expander to the input energy used to generate compressed air (power recovery efficiency). To achieve this, heat recovery of the compression heat, i.e., how much of the stored compression heat can be used to heat the compressed air that drives the expander, is important. Generally, when air at 20°C and atmospheric pressure is compressed to approximately 1.0 MPa, the air temperature is approximately 240°C. This means that the available energy for heat recovery via heat exchange via a heat storage medium is small, and the amount of heat recovered is small.

[0004] An example of a CAES device that performs such heat recovery is a compressed air storage power generation device as described in Patent Document 1. The compressed air storage power generation device described in Patent Document 1 not only heats the compressed air before expansion using a heat storage medium, but also uses external exhaust heat to heat the compressed air, thereby improving the power generation efficiency of the CAES device. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6649141 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the device described in Patent Document 1, the power generation efficiency of the CAES device is improved by utilizing external exhaust heat. Therefore, if there is no suitable external heat source, the power generation efficiency cannot be increased, and the power recovery efficiency, which is the ratio of output power to input power, cannot be improved. [Means for solving the problem]

[0007] A compressed air energy storage device according to one embodiment of the present invention comprises a compressor driven by an electric motor for compressing air, a first heat exchanger for heating a heat storage medium by heat exchange with the compressed air compressed by the compressor, a pressure storage tank for storing the compressed air after heat exchange in the first heat exchanger, an expander driven by the compressed air stored in the pressure storage tank, a generator driven by the expander, a second heat exchanger for heating the compressed air flowing into the expander by heat exchange with the heat storage medium heated in the first heat exchanger, and a heat pump device for absorbing heat from the heat storage medium after heat exchange in the second heat exchanger and releasing the heat to the compressed air that drives the expander. [Effects of the Invention]

[0008] According to the present invention, the compression heat in the CAES device can be efficiently recovered, thereby improving the efficiency of power recovery. [Brief explanation of the drawings]

[0009] [Figure 1]FIG. 1 is a diagram showing a schematic configuration of a compressed air energy storage device according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing a comparative example to the compressed air energy storage device according to the first embodiment. [Figure 3] FIG. 3 is a diagram showing a schematic configuration of a compressed air energy storage device according to a second embodiment of the present invention. [Figure 4] FIG. 4 is a diagram showing a schematic configuration of a compressed air energy storage device according to a third embodiment of the present invention. [Figure 5] FIG. 5 is a diagram showing a schematic configuration of a compressed air energy storage device according to a fourth embodiment of the present invention. [Figure 6] FIG. 6 is a diagram showing a schematic configuration of a compressed air energy storage device according to a fifth embodiment of the present invention. [Figure 7] FIG. 7 is a diagram showing a schematic configuration of a compressed air energy storage device according to a sixth embodiment of the present invention. [Figure 8] FIG. 8 is a diagram showing a schematic configuration of a compressed air energy storage device according to a seventh embodiment of the present invention. [Figure 9] FIG. 9 is a diagram showing a schematic configuration of a compressed air energy storage device according to an eighth embodiment of the present invention. [Figure 10] FIG. 10 is a diagram showing a schematic configuration of a compressed air energy storage device according to a ninth embodiment of the present invention. [Figure 11] FIG. 11 is a diagram showing an example of the schematic configuration of a compressed air energy storage device having a single stage configuration. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The following description and drawings are examples for explaining the present invention, and appropriate omissions and simplifications have been made for clarity of explanation. Furthermore, in the following description, identical or similar elements and processes are given the same reference numerals, and duplicate explanations may be omitted. Note that the content described below merely shows an example of an embodiment of the present invention, and the present invention is not limited to the following embodiment, and can be implemented in various other forms.

[0011] (First embodiment) 1 is a diagram showing a schematic configuration of a compressed air energy storage system (CAES system) according to a first embodiment of the present invention. The CAES system 1 is composed of a compressor unit 2A, an expander unit 2B, a heat storage unit 20, a heat pump unit 30, and a control device 40. The operations of the compressor unit 2A, the expander unit 2B, the heat storage unit 20, and the heat pump unit 30 are controlled by the control device 40.

[0012] The control device 40 is composed of a computer equipped with processing devices such as a CPU (Central Processing Unit), MPU (Micro Processing Unit), and DSP (Digital Signal Processor), non-volatile memory such as ROM (Read Only Memory), flash memory, and hard disk drive, volatile memory known as RAM (Random Access Memory), an input / output interface, and other peripheral circuits. These hardware components work together to run software and realize multiple functions. The controller may be composed of one computer or multiple computers. The processing device may be an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or the like.

[0013] The nonvolatile memory stores programs capable of executing various calculations. In other words, the nonvolatile memory is a storage medium (storage device) from which the programs that realize the functions of this embodiment can be read. The volatile memory is a storage medium (storage device) that temporarily stores the results of calculations performed by the processing device and signals input from the input interface. The processing device is a device that loads the programs stored in the nonvolatile memory into the volatile memory and executes calculations, and performs predetermined calculations on data taken from the input / output interface, the nonvolatile memory, and the volatile memory in accordance with the programs.

[0014] The compressor unit 2A includes motors (electric motors) 4 and 5, compressors 6 and 7, an accumulator tank 8, and an inverter device 9. The expander unit 2B includes expanders 10 and 11, generators 12 and 13, and a power conditioner 14. The compressors 6 and 7 and the expanders 10 and 11 may be of any type, such as a screw type, scroll type, turbo type, or reciprocating type. The heat storage unit 20 is a system in which a heat storage medium such as water circulates, and includes heat storage tanks 21 and 22, heat exchangers 24 to 27, and transfer pumps 28 and 29. The heat pump unit 30 is a heat pump device that employs a vapor compression cycle using a refrigerant, and includes a refrigerant compressor 31, an expansion valve 32, a radiator 34, and an evaporator 35.

[0015] The CAES device 1 is connected to a grid power 3 that includes a solar power generation device 18, a wind power generation device 19, etc. An inverter device 9 of the compressor unit 2A drives motors 4, 5, etc. with power supplied from the grid power 3. In addition, power generated by generators 12, 13 is supplied to the grid power 3 via a power conditioner 14.

[0016] Compressor 6, which performs the first-stage compression stroke, is rotationally driven by motor 4. Compressor 7, which performs the second-stage compression stroke, is rotationally driven by motor 5. These compressors 6, 7 perform two-stage compression of air. The suction port of compressor 6 is open to the atmosphere, and the discharge port of compressor 6 is connected to the suction port of second-stage compressor 7 via heat exchanger 24 of heat storage unit 20. The discharge port of compressor 7 is connected to accumulator tank 8 via heat exchanger 25 of heat storage unit 20.

[0017] Meanwhile, in the expansion machine unit 2B, the intake port of the expander 10 that performs the first-stage expansion stroke is connected to the pressure accumulator tank 8 via a heat exchanger 26 of the heat storage unit 20. The discharge port of the expander 10 is connected to the intake port of the expander 11 that performs the second-stage expansion stroke via a heat exchanger 27 of the heat storage unit 20. These expanders 10 and 11 perform two-stage expansion of the compressed air. The generator 12 is driven by the expander 10, and the generator 13 is driven by the expander 11, thereby generating power (power regeneration). The generators 12 and 13 are connected to the grid power 3 via a power conditioner 14, and the regenerated power is returned to the grid power 3.

[0018] The heat storage unit 20 includes a heat storage medium path that circulates the heat storage medium in the heat storage tank 22 through heat exchangers 24 and 25 connected in parallel and then flows into the heat storage tank 21, and a heat storage medium path that circulates the heat storage medium in the heat storage tank 21 through heat exchangers 26 and 27 connected in parallel and then flows into the heat storage tank 22. The heat storage medium in the heat storage tanks 21 and 22 is transferred by transfer pumps 28 and 29. A radiator 34 of the heat pump unit 30 is provided in the heat storage medium path between the heat storage tank 21 and the heat exchangers 26 and 27. Furthermore, an evaporator 35 of the heat pump unit 30 is provided in the heat storage medium path between the heat exchangers 26 and 27 and the heat storage tank 22.

[0019] The heat pump unit 30 configures a refrigeration cycle in which the refrigerant is compressed by the refrigerant compressor 31 and radiates heat in the radiator 34, and the refrigerant is then decompressed by the expansion valve 32, absorbs heat in the evaporator 35, and returns to the refrigerant compressor 31. The refrigerant compressor 31, which has a built-in motor, is driven by input power from the grid power 3. As described above, the radiator 34 is provided in the heat storage medium path between the heat storage tank 21 and the heat exchangers 26 and 27, and heat is radiated from the refrigerant to the heat storage medium in the radiator 34. The evaporator 35 is provided in the heat storage medium path returning from the heat exchangers 26 and 27 to the heat storage tank 22, and heat is absorbed from the heat storage medium to the refrigerant in the evaporator 35.

[0020] Next, we will explain the operation of the CAES apparatus 1. Note that, although the heat storage medium can be water, pressurized water, mineral oil-based or glycol-based heat storage medium, the following will explain an example in which water is used as the heat storage medium. (Charging operation) First, the charging operation for generating and storing compressed air will be described. During charging, the control device 40 operates the motors 4 and 5 and the transfer pump 29. When the transfer pump 29 is operated, the heat storage medium stored in the low-temperature heat storage tank 22 is supplied to the heat exchangers 24 and 25. As described above, by driving the compressor 6 with the motor 4 and the compressor 7 with the motor 5, the air drawn in through the intake port of the compressor 6 is compressed in two stages and discharged from the discharge port of the compressor 7. The high-temperature compressed air adiabatically compressed by the compressor 6 flows into the heat exchanger 24 and exchanges heat with the heat storage medium supplied from the low-temperature heat storage tank 22. As a result of this heat exchange, the low-temperature heat storage medium is heated to a high temperature of approximately 100°C and stored in the high-temperature heat storage tank 21.

[0021] The compressed air that has exchanged heat in heat exchanger 24 becomes low in temperature, approximately at room temperature, and is drawn into compressor 7, which is provided downstream of heat exchanger 24. The room-temperature compressed air drawn into compressor 7 undergoes second-stage adiabatic compression by compressor 7, becoming high-temperature, higher-pressure compressed air. The compressed air discharged from compressor 7 is introduced into heat exchanger 25, where it exchanges heat with the heat storage medium supplied from low-temperature heat storage tank 22. This heat exchange raises the low-temperature heat storage medium to a high temperature of approximately 100°C, and is stored in high-temperature heat storage tank 21. The compressed air that has exchanged heat in heat exchanger 25 becomes low in temperature, approximately at room temperature, and is stored in pressure storage tank 8. Through the above operations, compressed air energy is stored during charging.

[0022] (Discharge operation) Next, the discharge operation in which compressed air is used to drive the generator to generate electricity will be described. During the discharge operation, the control device 40 operates the transfer pump 28 and the heat pump unit 30 and supplies low-temperature, high-pressure compressed air stored in the pressure storage tank 8 to the heat exchanger 26. When the transfer pump 28 is operated, the heat storage medium stored in the high-temperature side heat storage tank 21 is supplied to the heat exchangers 26 and 27 via the radiator 34 of the heat pump unit 30. The temperature of the heat storage medium flowing from the heat storage tank 21 to the radiator 34 is approximately 70 to 90°C, depending on the storage time in the heat storage tank 21. The temperature of the refrigerant flowing into the radiator 34 is, for example, approximately 120°C. When the heat storage medium passes through the radiator 34, the temperature of the heat storage medium increases to approximately 100°C due to heat exchange with the refrigerant.

[0023] The compressed air that flows into heat exchanger 26 is heated to a high temperature of approximately 90°C by heat exchange with the high-temperature heat storage medium. The compressed air heated to approximately 90°C in heat exchanger 26 is supplied to expander 10, which is driven to perform the first stage of adiabatic expansion. The air adiabatically expanded by expander 10 flows into heat exchanger 27, which is provided between the discharge port of expander 10 and the suction port of expander 11. Meanwhile, the heat storage medium at approximately 100°C that flows into heat exchanger 26 is cooled to a low temperature of approximately 40°C by heat exchange with the compressed air, and flows into evaporator 35 of heat pump unit 30.

[0024] The heat storage medium heated to approximately 100°C by the radiator 34 of the heat pump unit 30 is also supplied to the heat exchanger 27 provided on the inlet side of the expander 11. The air adiabatically expanded by the expander 10 flows into the heat exchanger 27 and exchanges heat with the high-temperature heat storage medium, thereby becoming approximately 90°C. The air heated to approximately 90°C by the heat exchanger 27 is drawn into the expander 11 and undergoes a second stage of adiabatic expansion. The air adiabatically expanded by the expander 11 becomes low-temperature and low-pressure and is released into the atmosphere from the outlet of the expander 11. In this way, the low-temperature, high-pressure compressed air stored in the accumulator tank 8 is heated by the heat storage medium stored in the heat storage tank 21, and the heated compressed air drives the expanders 10 and 11, thereby generating electricity from the generators 12 and 13. The generated electricity is then supplied to the grid power 3 via the power conditioner 14.

[0025] The heat storage medium at approximately 100°C that flows into heat exchanger 27 is cooled to a low temperature of approximately 40°C through heat exchange and flows out of heat exchanger 27. The low-temperature heat storage medium that flows out of heat exchanger 27 joins with the heat storage medium that flows out of heat exchanger 26, and then flows into evaporator 35 of heat pump unit 30. In evaporator 35, heat exchange occurs between the low-temperature (approximately 40°C) heat storage medium that flows in from heat exchangers 26 and 27 and the refrigerant (approximately 20°C) whose temperature has been reduced by being decompressed by expansion valve 32. The heat storage medium whose temperature has been reduced to approximately 20°C through heat exchange in evaporator 35 flows into heat storage tank 22 and is stored therein. Meanwhile, the refrigerant absorbs heat from the heat storage medium in evaporator 35, evaporates, and returns to refrigerant compressor 31.

[0026] Next, an improvement in power recovery efficiency in this embodiment will be described. Fig. 2 is a diagram showing a comparative example of the CAES apparatus 1 of this embodiment. The CAES apparatus 100 shown in the comparative example in Fig. 2 does not include a heat pump unit 30, and other configurations are the same as those in Fig. 1.

[0027] In the CAES system 100, the heat storage medium stored in the heat storage tank 21 is supplied directly to the heat exchangers 26 and 27 without being heated, as in the configuration of FIG. 1. As described above, even if the temperature of the heat storage medium flowing into the heat storage tank 21 is approximately 100°C, the temperature of the heat storage medium supplied from the heat storage tank 21 to the heat exchangers 26 and 27 becomes approximately 70 to 90°C due to heat dissipation while stored in the heat storage tank 21. Therefore, the temperature of the compressed air that has exchanged heat with the heat storage medium and flows out of the heat exchangers 26 and 27 becomes approximately 70°C. Here, the power input to the inverter device 9 in FIG. 2 during charging operation is defined as E1, and the regenerated power generated by the compressed air produced by that power E1 is defined as E2. The power recovery efficiency in this case is E2 / E1, which is a value smaller than 1.

[0028] 1, the heat pump unit 30 absorbs thermal energy from the low-temperature heat storage medium returning from the heat exchangers 26, 27 to the heat storage tank 22, and releases the thermal energy to the high-temperature heat storage medium supplied from the heat storage tank 21 to the heat exchangers 26, 27, so that the temperature of the heat storage medium supplied to the heat exchangers 26, 27 is approximately 100°C. Therefore, the temperature of the compressed air flowing into the expanders 10, 11 rises to approximately 90°C, and the regenerative power generated by the generators 12, 13 becomes larger than in the configuration of FIG.

[0029] In the configuration shown in Fig. 1, in addition to the power E1 for generating compressed air, power ΔE1 for driving the refrigerant compressor 31 of the heat pump unit 30 is required, so the power input to the inverter device 9 is "E1 + ΔE1." Furthermore, in the case of Fig. 1, the temperature of the compressed air driving the expanders 10, 11 is approximately 90°C, which is higher than the approximately 70°C in the case of Fig. 2, so the regenerated power generated by the generators 12, 13 is "E2 + ΔE2," a value greater than E2. Therefore, the power recovery efficiency in this case is expressed as (E2 + ΔE2) / (E1 + ΔE1).

[0030] In order for the power recovery efficiency (E2 + ΔE2) / (E1 + ΔE1) to be greater than the power recovery rate (E2 / E1) in the case of FIG. 2, i.e., to satisfy [(E2 + ΔE2) / (E1 + ΔE1)] > (E2 / E1), the condition "(ΔE2 / ΔE1) > (E2 / E1) ... (1)" must be satisfied. The COP (coefficient of performance) of the refrigeration cycle formed by the heat pump unit 30 is approximately 3.0, and approximately three times the energy required to drive the refrigerant compressor 31 can be input to the thermal storage medium. This increases the available energy of the thermal storage medium, thereby satisfying the above-mentioned condition (1).

[0031] As described above, in the first embodiment, by providing the heat pump unit 30 as shown in Fig. 1 to absorb heat from the low-temperature heat storage medium and release it to the high-temperature heat storage medium, the heat of compression stored in the heat storage medium can be more efficiently recovered and transferred to the compressed air before expansion. As a result, the compressed air supplied to the expanders 10 and 11 can be heated to a higher temperature (approximately 90°C), thereby improving the efficiency of power recovery.

[0032] As in the comparative example of FIG. 2 , when the CAES apparatus 100 is not provided with the heat pump unit 30, the compressed air supplied to the expanders 10 and 11 is heated to approximately 70°C by heat exchange with a heat storage medium at 70 to 90°C. In contrast, in this embodiment, the compressed air is heated to approximately 90°C by heat exchange with a heat storage medium at approximately 100°C. In this case, the rate at which the temperature of the compressed air flowing out of the heat exchangers 26 and 27 rises is faster when the temperature of the heat storage medium is higher. Therefore, when the supply of the heat storage medium is started at the start of the discharge operation, the heat exchangers 26 and 27 are heated, and the temperature of the compressed air supplied to the expanders 10 and 11 reaches approximately 70°C in the case of FIG. 2 , in other words, the timing at which the amount of power generation reaches the same value as the amount of power generation in the case of FIG. 2 , is earlier than in the case of FIG. 2 . In other words, the responsiveness to fluctuations in power demand is improved.

[0033] (Second embodiment) 3 is a diagram showing a schematic configuration of a compressed air energy storage system (CAES system) according to a second embodiment of the present invention. In the following, the same components as those in the first embodiment are denoted by the same reference numerals, and redundant explanations will be omitted.

[0034] In the CAES apparatus 1A of the second embodiment shown in Fig. 3, a heat pump unit 30 includes a refrigerant compressor 31, an expansion valve 32, two radiators 34a and 34b, and an evaporator 35. The radiator 34a is provided in the compressed air path between the heat exchanger 26 and the expander 10. The radiator 34b is provided in the compressed air path between the heat exchanger 27 and the expander 11. The evaporator 35 is provided in the low-temperature side heat storage medium path between the heat exchangers 26 and 27 and the heat storage tank 22, as in the case of Fig. 1.

[0035] The heat pump unit 30 configures a refrigeration cycle in which refrigerant compressed in a refrigerant compressor 31 is split into two radiators 34a and 34b, each of which radiates heat, then merges again, is decompressed by an expansion valve 32, flows into an evaporator 35, absorbs heat in the evaporator 35, and returns to the refrigerant compressor 31. In the second embodiment, the temperature of the refrigerant flowing into the radiators 34a and 34b is set to approximately 130°C. The rest of the configuration is the same as that of the CAES apparatus 1 in FIG. 1.

[0036] Next, the operation of the CAES apparatus 1A will be described. Note that, although the heat storage medium can be water, pressurized water, mineral oil-based, glycol-based, or other heat storage media, the following description will be made taking the case where water is used as the heat storage medium as an example. Of the charging and discharging operations in the CAES apparatus 1A, the charging operation is the same as in the CAES apparatus 1 of Figure 1, so the discharging operation will be described below.

[0037] (Discharge operation) During discharge operation, the control device 40 operates the transfer pump 28 and the heat pump unit 30 and supplies low-temperature, high-pressure compressed air stored in the pressure accumulator tank 8 to the heat exchanger 26. When the transfer pump 28 is operated, the heat storage medium stored in the high-temperature side heat storage tank 21 is supplied to each of the heat exchangers 26, 27. The temperature of the heat storage medium supplied from the heat storage tank 21 to each of the heat exchangers 26, 27 is approximately 70 to 90°C. The low-temperature, high-pressure compressed air supplied from the pressure accumulator tank 8 to the heat exchanger 26 exchanges heat with the heat storage medium in the heat exchanger 26, and its temperature rises to approximately 70°C. Meanwhile, the temperature of the heat storage medium after heat exchange in the heat exchanger 26 becomes approximately 40°C, and flows into the evaporator 35 of the heat pump unit 30.

[0038] The compressed air that has passed through the heat exchanger 26 flows into the radiator 34a, where it exchanges heat with the high-temperature refrigerant, thereby further increasing its temperature. As described above, the temperature of the refrigerant that flows into the radiator 34a is set to approximately 130°C, so the temperature of the compressed air that exchanges heat with the refrigerant and flows into the expander 10 increases to approximately 120°C. The temperature of the refrigerant that flows out of the radiator 34a decreases to approximately 80°C due to heat exchange with the compressed air. The refrigerant at approximately 80°C that flows out of the radiator 34a returns to the expansion valve 32.

[0039] Compressed air at approximately 120°C that flows into the first-stage expander 10 undergoes first-stage adiabatic expansion in the expander 10, thereby driving the expander 10. The compressed air, whose pressure and temperature have been reduced by this adiabatic expansion, flows into the heat exchanger 27, where its temperature rises to approximately 70°C through heat exchange with the heat storage medium. Meanwhile, the temperature of the heat storage medium after heat exchange in the heat exchanger 27 becomes approximately 40°C, and after merging with the heat storage medium from the heat exchanger 26, flows into the evaporator 35 of the heat pump unit 30.

[0040] The compressed air that has passed through the heat exchanger 27 flows into the radiator 34b, where it exchanges heat with the high-temperature heat storage medium, thereby further increasing its temperature. As described above, the temperature of the refrigerant flowing into the radiator 34b is set to approximately 130°C, so the temperature of the compressed air that exchanges heat with the refrigerant and flows into the expander 10 rises to approximately 120°C. The compressed air at approximately 120°C that flows into the second-stage expander 11 drives the expander 11 by performing second-stage adiabatic expansion in the expander 11. The air adiabatically expanded by the expander 11 becomes low-temperature and low-pressure and is released to the atmosphere from the discharge port of the expander 11. In this way, the compressed air heated by the radiators 34a and 34b drives the expanders 10 and 11, generating electricity in the generators 12 and 13, which is then supplied to the grid power 3 via the power conditioner 14.

[0041] In the heat pump unit 30, the refrigerant flowing out of the radiator 34b exchanges heat with the compressed air to reduce its temperature to approximately 80°C, merges with the refrigerant flowing out of the radiator 34a, and returns to the expansion valve 32. The refrigerant flowing out of the radiators 34a and 34b at approximately 80°C expands in the expansion valve 32, reducing its temperature to approximately 20°C, and flows into the evaporator 35. In the evaporator 35, the refrigerant at approximately 20°C evaporates through heat exchange with the heat storage medium flowing in from the heat exchangers 26 and 27 at approximately 40°C. The evaporated refrigerant absorbs heat from the heat storage medium and is compressed by the refrigerant compressor 31 to a high temperature, which then dissipates heat to the compressed air in the radiators 34a and 34b. As a result, the temperature of the compressed air is heated from approximately 70°C to approximately 120°C, as described above.

[0042] In the first embodiment described above, the heat of the low-temperature heat storage medium is transferred to the high-temperature heat storage medium, and the compressed air is heated by the high-temperature heat storage medium. When water is used as the heat storage medium, the temperature can only be raised to about 100°C, so the compressed air can only be heated to about 90°C.

[0043] In contrast, in the second embodiment, heat absorbed from the low-temperature heat storage medium is directly radiated to the compressed air by the radiators 34a and 34b through which the refrigerant flows. Therefore, the compressed air flowing into the expanders 10 and 11 is heated by the radiators 34a and 34b to approximately 120°C, a higher temperature than in the first embodiment. This improves thermal efficiency compared to the configuration shown in FIG. 1, in which thermal energy recovered by the heat pump unit 30 is radiated to the compressed air via the heat storage medium. This allows the compressed air flowing into the expanders 10 and 11 to be heated to a higher temperature, thereby improving power recovery efficiency through increased power generation. Furthermore, in the second embodiment, the radiators 34a and 34b can heat the compressed air to a higher temperature, thereby quickly raising the temperature of the compressed air before expansion and improving responsiveness to fluctuations in power demand.

[0044] (Third embodiment) Fig. 4 is a diagram showing a schematic configuration of a compressed air energy storage system (CAES system) according to a third embodiment of the present invention. The CAES system 1B shown in Fig. 4 is configured such that the heat exchangers 26 and 27 in the configuration shown in Fig. 3 are replaced with three-fluid heat exchangers 26a and 27a. The refrigerant flowing out of the radiator 34a flows into the three-fluid heat exchanger 26a, and the refrigerant flowing out of the radiator 34b flows into the three-fluid heat exchanger 27a. In the following, the same components as those in the second embodiment are designated by the same reference numerals, and redundant explanations will be omitted.

[0045] The three-fluid heat exchangers 26a, 27a have a heat-dissipating fluid path, which includes a flow path through which a heat storage medium flows and a flow path through which a refrigerant flows, and a heat-absorbing fluid path, which includes a flow path through which compressed air flows. That is, in the three-fluid heat exchangers 26a, 27a, heat is transferred from the heat storage medium and the refrigerant to the compressed air, thereby heating the compressed air. Therefore, the three-fluid heat exchangers 26a, 27a can be considered both an element of the heat storage unit 20 and an element of the heat pump unit 30. The other configurations are similar to those shown in FIG. 3. While water, pressurized water, mineral oil, glycol, or other heat storage media can be used as the heat storage medium, the following description will be given using water as the heat storage medium.

[0046] The high-temperature refrigerant compressed by the refrigerant compressor 31 is divided and guided to radiators 34a and 34b, respectively. The refrigerant that exchanges heat with compressed air in radiator 34a flows into three-fluid heat exchanger 26a, and the refrigerant that exchanges heat with compressed air in radiator 34b flows into three-fluid heat exchanger 27a. The refrigerant that passed through three-fluid heat exchanger 26a and the refrigerant that passed through three-fluid heat exchanger 27a are combined and then adiabatically expanded in expansion valve 32, thereby decreasing their temperature. After adiabatically expanding, the refrigerant absorbs heat from the low-temperature heat storage medium in evaporator 35 and evaporates.

[0047] The temperature of the refrigerant compressed by the refrigerant compressor 31 is approximately 130°C. By exchanging heat with compressed air in the radiator 34a, the refrigerant temperature drops to approximately 80°C. Furthermore, by exchanging heat with compressed air in the three-fluid heat exchanger 26a, the refrigerant temperature drops to approximately 40°C. The same applies to the temperatures of the refrigerant that has passed through the radiator 34b and the three-fluid heat exchanger 27a; it is approximately 80°C at the outlet of the radiator 34b and approximately 40°C at the outlet of the three-fluid heat exchanger 27a. The temperatures of the heat storage medium at the inlet and outlet of the three-fluid heat exchangers 26a, 27a are approximately 80°C (inlet) and approximately 40°C (outlet). The refrigerant at approximately 40°C that flows out of the three-fluid heat exchangers 26a, 27a is adiabatically expanded in the expansion valve 32, thereby dropping in temperature.

[0048] In the configuration shown in FIG. 3 of the second embodiment, the temperature of the refrigerant flowing into the expansion valve 32 is approximately 80°C. However, in the configuration shown in FIG. 4, the temperature is lower, at approximately 40°C. This allows the refrigerant temperature after adiabatic expansion to be lowered, thereby increasing the amount of heat absorbed (heat recovered) from the heat storage medium to the refrigerant in the evaporator 35. That is, the input power ΔE1 (see conditional formula (1)) to the refrigerant compressor 31 when the compressed air is heated to approximately 120°C in the radiators 34a and 34b can be reduced. As a result, the power recovery efficiency can be further improved. Furthermore, by further heating the compressed air in the radiators 34a and 34b, the temperature of the compressed air flowing into the expanders 10 and 11 can be increased, thereby accelerating the rate at which the compressed air is heated and improving responsiveness to fluctuations in power demand.

[0049] (Fourth embodiment) FIG. 5 is a diagram showing the schematic configuration of a compressed air energy storage system (CAES system) according to a fourth embodiment of the present invention. The CAES system 1C shown in FIG. 5 differs from the CAES system 1 shown in FIG. 1 in the arrangement of the heat pump unit 30. Furthermore, in the CAES system 1C, the heat storage medium may reach a high temperature of 100°C or more, so a mineral oil-based or glycol-based heat storage medium, or pressurized water, is used. The other configuration is the same as that of the CAES system 1 shown in FIG. 1, and similar components are designated by the same reference numerals, and redundant explanations will be omitted.

[0050] In the CAES apparatus 1C, the evaporator 35 of the heat pump unit 30 is arranged in the low-temperature side heat storage medium path between the heat storage tank 22 and the heat exchangers 24, 25, and the radiator 34 is arranged in the high-temperature side heat storage medium path between the heat exchangers 24, 25 and the heat storage tank 21. The low-temperature heat storage medium stored in the heat storage tank 22 passes through the evaporator 35 of the heat pump unit 30 and is then supplied to the heat exchangers 24, 25 connected in parallel. The heat storage medium flowing out of the heat exchangers 24, 25 passes through the radiator 34 of the heat pump unit 30 and is then stored in the heat storage tank 21.

[0051] Next, the charging and discharging operations in the CAES apparatus 1C will be described. (Charging operation) During charging operation, control device 40 operates motors 4 and 5, heat pump unit 30, and transfer pump 29. Operation of motors 4 and 5 causes two-stage compression of the air by compressors 6 and 7. Operation of transfer pump 29 also causes the heat storage medium at approximately 40°C stored in low-temperature heat storage tank 22 to flow into evaporator 35 of heat pump unit 30. Heat is absorbed by the refrigerant in evaporator 35 of heat pump unit 30 from the heat storage medium flowing out of heat storage tank 22, and the temperature of the heat storage medium drops from approximately 40°C to approximately 20°C. The heat storage medium at approximately 20°C that flows out of evaporator 35 is diverted and flows into each of heat exchangers 24 and 25.

[0052] The high-temperature compressed air adiabatically compressed by the compressor 6 is discharged from the discharge port and flows into the heat exchanger 24, where it exchanges heat with a heat storage medium of approximately 20°C that is supplied to the heat exchanger 24. As a result of this heat exchange, the temperature of the heat storage medium becomes approximately 100°C. The compressed air that has exchanged heat in the heat exchanger 24 becomes a low temperature of approximately room temperature, and is drawn into the compressor 7 provided downstream of the heat exchanger 24. The room-temperature compressed air drawn into the compressor 7 undergoes a second stage of adiabatic compression by the compressor 7, becoming high-temperature, high-pressure compressed air. The compressed air discharged from the compressor 7 is introduced into the heat exchanger 25, where it exchanges heat with the heat storage medium of approximately 20°C that is supplied to the heat exchanger 25. As a result of this heat exchange, the temperature of the heat storage medium becomes approximately 100°C. The compressed air that has exchanged heat in the heat exchanger 25 becomes a low temperature of approximately room temperature, and is stored in the pressure accumulator tank 8.

[0053] The heat storage medium flowing out of the heat exchangers 24, 25 join together and then flow into the radiator 34 of the heat pump unit 30. In the radiator 34, heat is radiated from the refrigerant to the heat storage medium through heat exchange, and the temperature of the heat storage medium rises to approximately 120°C. The heat storage medium heated to approximately 120°C is stored in the heat storage tank 21 on the high-temperature side.

[0054] (Discharge operation) During the discharge operation, the control device 40 supplies the low-temperature, high-pressure compressed air stored in the pressure storage tank 8 to the heat exchanger 26, and also drives the transfer pump 28 to supply the heat storage medium in the high-temperature side heat storage tank 21 to the heat exchangers 26, 27. The temperature of the heat storage medium supplied to the heat exchangers 26, 27 becomes slightly lower than 120°C due to heat dissipation in the heat storage tank 21.

[0055] In the heat exchanger 26, heat exchange between the high-temperature heat storage medium and the compressed air raises the temperature of the compressed air to approximately 100°C, and the temperature of the heat storage medium drops to approximately 40°C. The compressed air heated to approximately 100°C in the heat exchanger 26 is drawn into the expander 10, where it undergoes a first-stage adiabatic expansion, driving the expander 10. The air adiabatically expanded by the expander 10 is supplied to the heat exchanger 27, where it exchanges heat with the heat storage medium and is heated to approximately 100°C. The air heated by the heat exchanger 27 is drawn into the expander 11, where it undergoes a second-stage adiabatic expansion, driving the expander 11. The air adiabatically expanded by the expander 11 becomes low-temperature and low-pressure and is released into the atmosphere from the outlet of the expander 11. The expanders 10 and 11 are driven by the compressed air, and power is generated by the generators 12 and 13. The generated power is supplied to the grid power 3 via the power conditioner 14.

[0056] In the first embodiment described above, water with a boiling point of 100°C is used as the heat storage medium, and the heat pump unit 30 transfers heat from the low-temperature heat storage medium flowing out of the heat exchangers 26, 27 to the heat storage medium flowing into the heat exchangers 26, 27, thereby heating the temperature of the air supplied to the expanders 10, 11 to approximately 90°C. On the other hand, in the fourth embodiment, a heat storage medium with a high boiling point, such as pressurized water, is used, and heat is transferred from the low-temperature heat storage medium to the high-temperature heat storage medium by the heat pump unit 30, thereby storing a higher temperature (approximately 120°C) heat storage medium in the heat storage tank 21. By supplying the higher temperature (approximately 120°C) heat storage medium stored in the heat storage tank 21 to the heat exchangers 26, 27, the temperature of the compressed air supplied to the expanders 10, 11 is heated to approximately 100°C.

[0057] Therefore, the temperature of the compressed air supplied to the expanders 10, 11 can be made higher than in the first embodiment, thereby improving the efficiency of power recovery. Also, since the temperature of the heat storage medium flowing into the heat exchangers 26, 27 can be made higher, the time required to raise the temperature of the compressed air by heat exchange can be shortened, improving the responsiveness to fluctuations in power demand.

[0058] (Fifth embodiment) Fig. 6 is a diagram showing a schematic configuration of a compressed air energy storage system (CAES system) according to a fifth embodiment of the present invention. The CAES system 1D shown in Fig. 6 differs from the CAES system 1 shown in Fig. 1 in the configuration of the compressor unit 2A and the arrangement of the heat pump unit 30. The other configuration is the same as the configuration shown in Fig. 1, and the same components are denoted by the same reference numerals and redundant explanations will be omitted.

[0059] 6, a compressor unit 2A includes multiple accumulator tanks 8a, 8b, and 8c, and further includes on-off valves V1, V2, V3, and V4 for switching the flow path of compressed air. The discharge port of the second-stage compressor 7 is connected to a heat exchanger 25 via on-off valve V1, and is also connected to an accumulator tank 8a, in which high-temperature, high-pressure compressed air is stored, via on-off valve V2. The outlet of the accumulator tank 8a is connected to a suction port of the expander 10 via on-off valve V3 and a radiator 34 of a heat pump unit 30.

[0060] The compressed air outlet of the heat exchanger 25 is connected to the accumulator tanks 8b and 8c in which low-temperature, high-pressure compressed air is stored. The accumulator tanks 8b and 8c are connected by piping. The accumulator tank 8c is connected to the suction port of the expander 10 via the open / close valve V4 and the heat exchanger 26 of the expander unit 2B. Note that because heat is easily dissipated in the accumulator tank 8a in which the high-temperature, high-pressure heat storage medium is stored, the volume of the accumulator tank 8a is set smaller than the combined volume of the accumulator tanks 8b and 8c in which the low-temperature, high-pressure compressed air is stored.

[0061] The evaporator 35 of the heat pump unit 30 is provided in a low-temperature heat storage medium path that returns from the heat exchangers 26, 27 to the heat storage tank 22. On the other hand, the radiator 34 is provided in a path of high-temperature, high-pressure compressed air that is supplied from the pressure storage tank 8a to the expander 10. The heat pump unit 30 absorbs heat from the low-temperature heat storage medium in the evaporator 35 and radiates the heat to the compressed air by the radiator 34. As a result, the high-temperature, high-pressure compressed air that is supplied from the pressure storage tank 8a to the expander 10 is heated by the radiator 34 and becomes even hotter.

[0062] Next, the charging and discharging operations of the CAES apparatus 1D will be described. Note that, although the heat storage medium can be water, pressurized water, mineral oil, glycol, or other heat storage media, the following description will be made taking the case where water is used as the heat storage medium as an example. (Charging operation) In the charging operation, the control device 40 first opens the on-off valves V1 and V2. Note that when the CAES apparatus 1D is in an operation-stop state, the on-off valves V1 to V4 are all closed. Next, the control device 40 drives the compressors 6 and 7 using the motors 4 and 5, and drives the transfer pump 29 to supply the heat storage medium stored in the heat storage tank 22 to the heat exchangers 24 and 25.

[0063] The high-temperature compressed air adiabatically compressed by the compressor 6 is discharged from the discharge port and flows into the heat exchanger 24, where it exchanges heat with a heat storage medium of about 20°C that is supplied to the heat exchanger 24. This heat exchange raises the temperature of the heat storage medium to about 100°C, and the heat storage medium flows out of the heat exchanger 24. The compressed air that has exchanged heat in the heat exchanger 24 is cooled to about room temperature, and is drawn into the compressor 7 provided downstream of the heat exchanger 24. The room-temperature compressed air drawn into the compressor 7 is subjected to a second-stage adiabatic compression by the compressor 7, and becomes high-temperature, high-pressure compressed air.

[0064] The high-temperature, high-pressure compressed air discharged from the compressor 7 flows into the pressure accumulator tank 8a through the on-off valve V2 and into the heat exchanger 25 through the on-off valve V1. The temperature of the compressed air discharged after second-stage adiabatic compression in the compressor 7 is approximately 130°C, so the temperature of the compressed air stored in the pressure accumulator tank 8a is approximately 120°C. The compressed air introduced into the heat exchanger 25 exchanges heat with a heat storage medium at approximately 20°C, and is cooled to approximately room temperature, before being stored in the pressure accumulator tanks 8b and 8c. The temperature of the heat storage medium flowing out of the heat exchanger 25 becomes approximately 100°C due to the heat exchange with the compressed air. The heat storage medium flowing out of the heat exchanger 25 merges with the heat storage medium flowing out of the heat exchanger 24, and then flows into the heat storage tank 21 to be stored.

[0065] Next, when the pressure in the accumulator tank 8a reaches a preset specified pressure value, the on-off valve V2 is closed to terminate the storage of compressed air in the accumulator tank 8a. As a result, all of the high-temperature, high-pressure compressed air discharged from the compressor 7 flows into the heat exchanger 25 through the on-off valve V1. In the heat exchanger 25, heat is transferred from the high-temperature compressed air to the heat storage medium, which is heated to approximately 100°C, and the compressed air becomes low, approximately at room temperature. The low-temperature, high-pressure compressed air flowing out of the heat exchanger 25 flows into and is stored in the accumulator tanks 8b and 8c. Meanwhile, the high-temperature (approximately 100°C) heat storage medium flowing out of the heat exchanger 25 merges with the high-temperature heat storage medium flowing out of the heat exchanger 24 and then flows into and is stored in the heat storage tank 21. Then, when the pressure in the accumulator tanks 8b and 8c reaches a specified pressure value, the control device 40 closes the on-off valve V1 and stops the transfer pump 28 to terminate the charging operation.

[0066] (Discharge operation) When the discharge operation starts, the control device 40 operates the transfer pump 28 and the heat pump unit 30 and also opens the on-off valve V3. The operation of the transfer pump 28 supplies the high-temperature heat storage medium stored in the heat storage tank 21 to the heat exchangers 26, 27. When the on-off valve V3 is opened, compressed air at approximately 120°C stored in the pressure storage tank 8a is supplied to the expander 10 via the radiator 34 of the heat pump unit 30. The compressed air from the pressure storage tank 8a is heated to a high temperature of approximately 150°C by heat exchange with the high-temperature refrigerant in the radiator 34, and then supplied to the expander 10.

[0067] The compressed air at approximately 150°C supplied to the expander 10 is adiabatically expanded in the expander 10 to reduce its temperature. The reduced-temperature compressed air is heated to approximately 70°C by the heat exchanger 27 and then supplied to the second-stage expander 11. The air adiabatically expanded by the expander 11 then becomes low-temperature and low-pressure and is released to the atmosphere from the discharge port of the expander 11. The expanders 10 and 11 are driven by the compressed air, and power is generated by the generators 12 and 13.

[0068] When the pressure in accumulator tank 8a drops below the pressure required for power generation, or when a predetermined warm-up time has elapsed, on-off valve V3 is closed, on-off valve V4 is opened, and heat pump unit 30 is stopped. This switches the compressed air supply source from accumulator tank 8a to accumulator tanks 8b and 8c. The low-temperature, high-pressure compressed air in accumulator tanks 8b and 8c passes through on-off valve V4 and flows into heat exchanger 26. The volume of accumulator tank 8a is set so that the time it takes for the pressure to drop below the pressure required for power generation is sufficiently longer than the predetermined warm-up time.

[0069] The compressed air that flows into the heat exchanger 26 is heated to about 70°C by heat exchange with the heat storage medium and is adiabatically expanded in the expander 10 to drive the expander 10. The air that has been adiabatically expanded by the expander 10 and has been cooled is then heat exchanged with a high-temperature heat storage medium in the heat exchanger 27, where it is heated again to a high temperature of about 70°C and is then supplied to the expander 11. The compressed air supplied to the expander 11 undergoes a second-stage adiabatic expansion in the expander 11, where it becomes a low-temperature, low-pressure state, and is then released to the atmosphere from the discharge port of the expander 11.

[0070] The warm-up time will now be described. In the heat exchangers 26, 27, heat is exchanged between the heat storage medium and the compressed air. Since the heat exchangers 26, 27 are not sufficiently warmed immediately after the supply of the heat storage medium begins, if the supplied compressed air is low-temperature and high-pressure, the heat exchangers 26, 27 are unable to heat the compressed air to a high temperature of approximately 70°C. This prevents the expanders 10, 11 from rotating at their predetermined speeds, preventing the generators 12, 13 from generating sufficient power. Here, the time from the start of the supply of the heat storage medium to the heat exchangers 26, 27 until the heat exchangers 26, 27 are sufficiently warmed up and able to heat the compressed air to approximately 70°C is referred to as the warm-up time or warm-up period.

[0071] In this embodiment, the supply of the heat storage medium to the heat exchangers 26, 27 starts when the charging operation starts, and then, after the warm-up time or a longer time has elapsed, the compressed air supply source is switched to the pressure accumulator tanks 8b, 8c. Therefore, when the compressed air supply source is switched to the pressure accumulator tanks 8b, 8c, it is possible to prevent a decrease in generated power due to insufficient warm-up of the heat exchangers 26, 27.

[0072] Furthermore, during the period from the start of the discharge operation, including the warm-up period, until the on-off valve V4 is switched to the open position, high-temperature, high-pressure compressed air stored in the accumulator tank 8a is heated to approximately 150°C by the radiator 34 and supplied to the expander 10. As a result, the expander 10 can quickly rise to the rotation speed required when compressed air of approximately 150°C is supplied as soon as the discharge operation begins. In other words, responsiveness to fluctuations in power demand can be improved. Furthermore, during the discharge operation using compressed air stored in the accumulator tank 8a, compressed air of approximately 150°C is supplied to the expander 10, thereby improving power recovery efficiency compared to the configuration of FIG. 2, in which compressed air of approximately 70°C is supplied to the expanders 10, 11.

[0073] In the charging operation described above, the on-off valves V1 and V2 are opened when charging starts, and the storage of high-temperature, high-pressure compressed air in the accumulator tank 8a and the storage of low-temperature, high-pressure compressed air in the accumulator tanks 8b and 8c are simultaneously started. However, after the on-off valve V1 is closed and the on-off valve V2 is opened to store high-temperature compressed air in the accumulator tank 8a, the on-off valve V1 may be opened and the on-off valve V2 may be closed to store low-temperature compressed air in the accumulator tanks 8b and 8c.

[0074] For example, when leveling power generation using wind power, changes in wind direction and other factors can necessitate multiple power generation cycles throughout the day, resulting in a short operating time for each power generation cycle. This significantly impacts the low-efficiency operation required for the system to warm up to a desired temperature. In such cases, during charging, the on-off valve V1 can be closed and the on-off valve V2 can be opened to store high-temperature compressed air in the accumulator tank 8a. This allows the accumulator tank 8a to initially fill up to a specified pressure level. This allows subsequent repeated power generation to be achieved using only the high-temperature, high-pressure compressed air stored in the accumulator tank 8a. This approach is effective when applied to power leveling grid power, where the supply share of wind power, which generates electricity at relatively short intervals due to large fluctuations in power demand, is high. On the other hand, in the case of solar power generation, discharge occurs approximately once a day, so either valve opening / closing pattern is acceptable.

[0075] (Sixth embodiment) Fig. 7 is a diagram showing a schematic configuration of a compressed air energy storage system (CAES system) according to a sixth embodiment of the present invention. In the CAES system 1E shown in Fig. 7, the accumulator tanks 8b and 8c are connected to the heat exchanger 26 via the on-off valve V4. The compressed air outlet side of the heat exchanger 26 is connected to the compressed air supply line between the on-off valve V3 and the radiator 34 via the on-off valve V5. The other configurations are the same as those of the CAES system 1D shown in Fig. 6.

[0076] As described above, in the CAES apparatus 1D shown in Fig. 6, the high-temperature, high-pressure compressed air supplied from the accumulator tank 8a to the expander 10 is heated in the radiator 34, and the higher-temperature compressed air is supplied to the expander 10. On the other hand, in the CAES apparatus 1E shown in Fig. 7, not only the high-temperature, high-pressure compressed air supplied from the accumulator tank 8a to the expander 10, but also the low-temperature, high-pressure compressed air supplied from the accumulator tanks 8b and 8c to the expander 10 is heated in the radiator 34 before being supplied to the expander 10. Regarding the operation of the CAES apparatus 1E, the charging operation is the same as in the case of the CAES apparatus 1D shown in Fig. 6, and only the discharging operation will be described below.

[0077] (Discharge operation) When the discharge operation starts, the control device 40 operates the transfer pump 28 and the heat pump unit 30, opens the on-off valve V3, and closes the on-off valves V4 and V5. The operation of the transfer pump 28 supplies the high-temperature heat storage medium stored in the heat storage tank 21 to the heat exchangers 26 and 27. When the on-off valve V3 is opened, the high-temperature, high-pressure compressed air stored in the accumulator tank 8a is supplied to the expander 10 via the radiator 34 of the heat pump unit 30. The high-temperature, high-pressure compressed air from the accumulator tank 8a is further heated by heat exchange with the high-temperature refrigerant in the radiator 34, and then supplied to the expander 10. As a result, power is generated using the compressed air stored in the accumulator tank 8a.

[0078] Next, when the pressure in the accumulator tank 8a drops below the pressure required for power generation, or when a predetermined warm-up time has elapsed, the control device 40 closes the on-off valve V3 and opens the on-off valves V4 and V5. This switches the compressed air supply source from the accumulator tank 8a to the accumulator tanks 8b and 8c. The low-temperature, high-pressure compressed air from the accumulator tanks 8b and 8c passes through the on-off valve V4 and flows into the heat exchanger 26. The compressed air that flows into the heat exchanger 26 is heated by heat exchange with the heat storage medium and then flows into the radiator 34 of the heat pump unit 30 via the on-off valve V5. The compressed air from the accumulator tanks 8b and 8c, whose temperature has been raised by the heat exchanger 26, is further heated by heat exchange with the high-temperature refrigerant in the radiator 34 and then supplied to the expander 10. As a result, power is generated using the compressed air stored in the accumulator tanks 8b and 8c.

[0079] As described above, in the CAES system 1E, not only is the high-temperature, high-pressure compressed air supplied from the accumulator tank 8a to the expander 10 heated by the radiator 34, but also the low-temperature, high-pressure compressed air supplied from the accumulator tanks 8b and 8c to the expander 10 is heated by the heat storage medium in the heat exchanger 26 and then further heated by the radiator 34. In this embodiment, similar to the CAES system 1D, when the compressed air supply source is switched to the accumulator tanks 8b and 8c, a decrease in power generation due to insufficient warm-up of the heat exchangers 26 and 27 can be prevented. Furthermore, the expander 10 can quickly start up upon the start of discharging operation, thereby improving responsiveness to fluctuations in power demand. Furthermore, power recovery efficiency can be improved not only during the discharging operation using the compressed air from the accumulator tank 8a, but also during the discharging operation using the low-temperature, high-pressure compressed air from the accumulator tanks 8b and 8c.

[0080] (Seventh embodiment) Fig. 8 is a diagram showing a schematic configuration of a compressed air energy storage system (CAES system) according to a seventh embodiment of the present invention. In the CAES system 1F shown in Fig. 8, the accumulator tank 8a is connected to the expander 10 via an on-off valve V3. The accumulator tanks 8b and 8c are connected to the heat exchanger 26 via an on-off valve V4. The compressed air outlet side of the heat exchanger 26 is connected to the radiator 34. The compressed air outlet side of the radiator 34 is connected to the expander 10 via an on-off valve V6. The other configurations are the same as those of the CAES system 1D shown in Fig. 6.

[0081] As described above, in the CAES apparatus 1D shown in Fig. 6, the high-temperature, high-pressure compressed air supplied from the accumulator tank 8a to the expander 10 is heated in the radiator 34, and the higher-temperature compressed air is supplied to the expander 10. On the other hand, in the CAES apparatus 1F shown in Fig. 8, only the low-temperature, high-pressure compressed air supplied from the accumulator tanks 8b and 8c to the expander 10 is heated in the radiator 34 before being supplied to the expander 10. Regarding the operation of the CAES apparatus 1F, the charging operation is the same as in the case of the CAES apparatus 1D shown in Fig. 6, and only the discharging operation will be described below.

[0082] (Discharge operation) When the discharge operation starts, the control device 40 operates the transfer pump 28 and the heat pump unit 30, opens the on-off valve V3, and closes the on-off valves V4 and V6. The operation of the transfer pump 28 supplies the high-temperature heat storage medium stored in the heat storage tank 21 to the heat exchangers 26 and 27. When the on-off valve V3 is opened, the high-temperature, high-pressure compressed air stored in the pressure storage tank 8a is supplied to the expander 10. As a result, power is generated using the compressed air stored in the pressure storage tank 8a.

[0083] Next, when the pressure in the accumulator tank 8a drops below the pressure required for power generation, or when a predetermined warm-up time has elapsed, the control device 40 closes the on-off valve V3 and opens the on-off valves V4 and V6. This switches the compressed air supply source from the accumulator tank 8a to the accumulator tanks 8b and 8c. The low-temperature, high-pressure compressed air from the accumulator tanks 8b and 8c passes through the on-off valve V4 and flows into the heat exchanger 26. The compressed air that flows into the heat exchanger 26 is heated by heat exchange with the heat storage medium and then flows into the radiator 34 of the heat pump unit 30. The compressed air from the accumulator tanks 8b and 8c, whose temperature has been raised by the heat exchanger 26, is further heated by heat exchange with the high-temperature refrigerant in the radiator 34 and then supplied to the expander 10 via the on-off valve V6. As a result, power is generated using the compressed air stored in the accumulator tanks 8b and 8c.

[0084] In this way, in the CAES system 1F, the low-temperature, high-pressure compressed air supplied from the accumulator tanks 8b and 8c to the expander 10 is heated by the heat storage medium in the heat exchanger 26, and then further heated in the radiator 34 before being supplied to the expander 10. This improves the power recovery efficiency during the discharge operation period using the low-temperature, high-pressure compressed air from the accumulator tanks 8b and 8c. Furthermore, when the compressed air supply source is switched to the accumulator tanks 8b and 8c, the heat exchangers 26 and 27 have already been warmed up, preventing a decrease in power generation during the switchover. Furthermore, since the high-temperature, high-pressure compressed air stored in the accumulator tank 8a is supplied to the expander 10 at the start of discharge, the expander 10 can quickly start up at the start of discharge, improving responsiveness to fluctuations in power demand.

[0085] (Eighth embodiment) FIG. 9 is a diagram showing a schematic configuration of a compressed air energy storage system (CAES system) according to an eighth embodiment of the present invention. In the CAES system 1G shown in FIG. 9, the accumulator tank 8a is connected to the expander 10 via an on-off valve V3. The accumulator tanks 8b and 8c are connected to the radiator 34a via an on-off valve V4. The compressed air outlet side of the radiator 34a is connected to the heat exchanger 26. The compressed air outlet side of the heat exchanger 26 is connected to the expander 10 via an on-off valve V7. The discharge side of the expander 10 is connected to the heat exchanger 27 via an on-off valve V8 and to the radiator 34b via an on-off valve V9. The compressed air outlet side of the radiator 34b is connected to the heat exchanger 27.

[0086] The refrigerant discharged from the refrigerant compressor 31 of the heat pump unit 30 is divided and flows into the radiators 34a and 34b. The refrigerant flowing out from the radiators 34a and 34b joins together and then flows into the expansion valve 32. The refrigerant adiabatically expanded in the expansion valve 32 is divided and flows into the evaporators 35a and 35b. The refrigerant flowing out from the evaporators 35a and 35b joins together and then returns to the refrigerant compressor 31.

[0087] The heat storage medium in the high-temperature side heat storage tank 21 is supplied to the heat exchangers 26 and 27 by the transfer pump 28. The heat storage medium flowing out of the heat exchangers 26 and 27 joins together and then flows into the evaporators 35a and 35b, respectively. The heat storage medium flowing out of the evaporators 35a and 35b joins together and then returns to the low-temperature side heat storage tank 22. The other configurations are the same as those of the CAES apparatus 1D shown in Figure 6. Regarding the operation of the CAES apparatus 1G, the charging operation is the same as that of the CAES apparatus 1D shown in Figure 6, and only the discharging operation will be described below.

[0088] (Discharge operation) Upon starting the discharge operation, the control device 40 operates the transfer pump 28 and the heat pump unit 30, opens the on-off valves V3 and V8, and closes the on-off valves V4, V7, and V9. The operation of the transfer pump 28 supplies the high-temperature heat storage medium stored in the heat storage tank 21 to the heat exchangers 26 and 27, and the heat storage medium flowing out of the heat exchangers 26 and 27 passes through the evaporators 35a and 35b and returns to the heat storage tank 22. When the on-off valve V3 is opened, high-temperature, high-pressure compressed air stored in the pressure storage tank 8a is supplied to the expander 10. The air adiabatically expanded in the expander 10 flows into the heat exchanger 27 through the on-off valve V8. The air heated by the heat storage medium in the heat exchanger 27 undergoes a second-stage adiabatic expansion in the expander 11 and is released into the atmosphere. As a result, power is generated using the compressed air stored in the pressure storage tank 8a.

[0089] Next, when the pressure in the accumulator tank 8a drops below the pressure required for power generation, or when a predetermined warm-up time has elapsed, the control device 40 closes the on-off valves V3 and V8 and opens the on-off valves V4, V7, and V9. This switches the compressed air supply source from the accumulator tank 8a to the accumulator tanks 8b and 8c. The low-temperature, high-pressure compressed air in the accumulator tanks 8b and 8c passes through the on-off valve V4 and flows into the radiator 34a. The compressed air is heated and raised in temperature by the radiator 34a before flowing into the heat exchanger 26. The compressed air is heated by the heat storage medium in the heat exchanger 26, further increasing its temperature, and is then supplied to the expander 10 via the on-off valve V7. The compressed air adiabatically expanded in the expander 10 passes through the on-off valve V9 and flows into the radiator 34b. The compressed air heated by the refrigerant in the radiator 34b flows into the heat exchanger 27, where it is heated by the heat storage medium and its temperature further increases. The compressed air flowing out of the heat exchanger 27 is supplied to the expander 11, where it undergoes a second-stage adiabatic expansion. In this way, power is generated using the compressed air stored in the accumulator tanks 8b and 8c.

[0090] In the CAES system 1G, high-temperature, high-pressure compressed air stored in the accumulator tank 8a is supplied to the expander 10 when discharge begins, allowing the expander 10 to quickly start up as soon as discharge begins, thereby improving responsiveness to fluctuations in power demand. Furthermore, when the compressed air supply source is switched to the accumulator tanks 8b and 8c, the heat exchangers 26 and 27 have already been warmed up, preventing a decrease in power generation during the switchover. Furthermore, when discharge is performed using the low-temperature, high-pressure compressed air from the accumulator tanks 8b and 8c, the air heated by the radiator 34a is further heated by the heat exchanger 26 and supplied to the expander 10. Similarly, the air heated by the radiator 34b is further heated by the heat exchanger 27 and supplied to the expander 11, improving power recovery efficiency.

[0091] (Ninth embodiment) Fig. 10 is a diagram showing a schematic configuration of a compressed air energy storage system (CAES system) according to a ninth embodiment of the present invention. The CAES system 1H shown in Fig. 10 is a modified version of the CAES system 1C shown in Fig. 5, which uses the heat pump unit 30 during charging, but includes multiple pressure accumulator tanks 8a, 8b, and 8c instead of the pressure accumulator tank 8. Since the heat storage medium can reach a high temperature of 100°C or higher, pressurized water, a mineral oil-based medium, a glycol-based medium, or the like is used as the heat storage medium.

[0092] (Charging operation) In charging operation, the control device 40 first opens the on-off valves V1 and V2. Then, the motors 4 and 5, the heat pump unit 30, and the transfer pump 29 are driven by input power from the grid power 3. This causes two-stage compression of the air by the compressors 6 and 7. Furthermore, by driving the transfer pump 29, the heat storage medium at approximately 40°C stored in the low-temperature side heat storage tank 22 is supplied to the heat exchangers 24 and 25 via the evaporator 35. The heat storage medium flowing out of the heat storage tank 22 absorbs heat into the refrigerant in the evaporator 35 of the heat pump unit 30, and its temperature drops from approximately 40°C to approximately 20°C. The heat storage medium at approximately 20°C flowing out of the evaporator 35 is divided and flows into each of the heat exchangers 24 and 25.

[0093] The high-temperature compressed air adiabatically compressed by the compressor 6 is discharged from the discharge port and flows into the heat exchanger 24, where it exchanges heat with a heat storage medium of about 20°C that is supplied to the heat exchanger 24. This heat exchange raises the temperature of the heat storage medium to about 100°C, and the heat storage medium flows out of the heat exchanger 24. The compressed air that has exchanged heat in the heat exchanger 24 is cooled to about room temperature, and is drawn into the compressor 7 provided downstream of the heat exchanger 24. The room-temperature compressed air drawn into the compressor 7 is subjected to a second-stage adiabatic compression by the compressor 7, and becomes high-temperature, higher-pressure compressed air.

[0094] The high-temperature, high-pressure compressed air discharged from the compressor 7 is stored in the accumulator tank 8a via the on-off valve V2, and also passes through the heat exchanger 25 via the on-off valve V1 before being stored in the accumulator tanks 8b and 8c. Since the temperature of the compressed air discharged after second-stage adiabatic compression in the compressor 7 is approximately 130°C, the temperature of the compressed air stored in the accumulator tank 8a is approximately 120°C. The compressed air introduced into the heat exchanger 25 exchanges heat with a heat storage medium at approximately 20°C, and is then cooled to approximately room temperature before being stored in the accumulator tanks 8b and 8c. The temperature of the heat storage medium flowing out of the heat exchanger 25 is increased to approximately 100°C due to heat exchange with the compressed air.

[0095] The heat storage medium flowing out of the heat exchangers 24, 25 join together and then flow into the radiator 34 of the heat pump unit 30. In the radiator 34, heat is radiated from the refrigerant to the heat storage medium through heat exchange, and the temperature of the heat storage medium rises to approximately 120°C. The heat storage medium heated to approximately 120°C is stored in the heat storage tank 21 on the high-temperature side.

[0096] Next, when the pressure in accumulator tank 8a reaches a specified pressure value, on-off valve V2 is closed to terminate the storage of compressed air in accumulator tank 8a. As a result, all of the high-temperature, high-pressure compressed air discharged from compressor 7 flows into heat exchanger 25 through on-off valve V1. In heat exchanger 25, heat is transferred from the high-temperature compressed air to the heat storage medium, which is heated to approximately 100°C, and the compressed air becomes low, approximately at room temperature. The low-temperature, high-pressure compressed air flowing out of heat exchanger 25 flows into accumulator tanks 8b and 8c and is stored there.

[0097] (Discharge operation) When the discharge operation starts, the control device 40 operates the transfer pump 28 and opens the on-off valve V3. The operation of the transfer pump 28 supplies the high-temperature heat storage medium stored in the heat storage tank 21 to the heat exchangers 26 and 27. When the on-off valve V3 is opened, compressed air at approximately 120°C stored in the pressure storage tank 8a is supplied to the expander 10 via the radiator 34 of the heat pump unit 30. The compressed air at approximately 120°C supplied to the expander 10 is adiabatically expanded in the expander 10 to reduce its temperature. The reduced-temperature compressed air is then heated to approximately 100°C by the heat exchanger 27 and supplied to the second-stage expander 11. The air adiabatically expanded by the expander 11 is then in a low-temperature, low-pressure state and released to the atmosphere from the discharge port of the expander 11. The expanders 10 and 11 are driven by the compressed air, and electricity is generated by the generators 12 and 13.

[0098] When the pressure in accumulator tank 8a drops below the pressure required for power generation, or when a predetermined warm-up time has elapsed, on-off valve V3 is closed and on-off valve V4 is opened to switch the compressed air supply source from accumulator tank 8a to accumulator tanks 8b and 8c. Low-temperature, constant-pressure compressed air from accumulator tanks 8b and 8c passes through on-off valve V4 and flows into heat exchanger 26. The compressed air that flows into heat exchanger 26 is heated to approximately 70°C by heat exchange with the heat storage medium and is adiabatically expanded in expander 10 to drive expander 10. The air that has been adiabatically expanded by expander 10 and has been cooled to a high temperature of approximately 70°C again is heat exchanged with the high-temperature heat storage medium in heat exchanger 27 and is then supplied to expander 11. The compressed air supplied to expander 11 undergoes second-stage adiabatic expansion in expander 11, resulting in a low-temperature, low-pressure state, and is then released to the atmosphere through the discharge port of expander 11.

[0099] In this embodiment, as in the case of the CAES apparatus 1D in Fig. 6, the supply of the heat storage medium to the heat exchangers 26, 27 starts when the charging operation starts, and then, after a warm-up time or a longer time has elapsed, the on-off valve V4 is opened to switch the compressed air supply source to the accumulator tanks 8b, 8c. Therefore, when the compressed air supply source is switched to the accumulator tanks 8b, 8c, it is possible to prevent a decrease in generated power due to insufficient warm-up of the heat exchangers 26, 27.

[0100] 5, in this embodiment, a heat storage medium with a high boiling point, such as pressurized water, is used, and heat is transferred from the low-temperature heat storage medium to the high-temperature heat storage medium by the heat pump unit 30, so that a higher-temperature (approximately 120°C) heat storage medium is stored in the heat storage tank 21. By supplying the higher-temperature (approximately 120°C) heat storage medium stored in the heat storage tank 21 to the heat exchangers 26, 27, the temperature of the air supplied to the expanders 10, 11 is heated to approximately 100°C, which is higher than in the first embodiment. As a result, it is possible to improve the power recovery efficiency.

[0101] Furthermore, during the period from the start of the discharge operation, including the warm-up period, until the on-off valve V4 is switched to open, high-temperature, high-pressure compressed air stored in the accumulator tank 8a is supplied to the expander 10. As a result, the expander 10 can start up quickly upon the start of the discharge operation, thereby improving responsiveness to fluctuations in power demand.

[0102] In each of the above-described embodiments, a two-stage compression / two-stage expansion type is used with compressors 6, 7 and expanders 10, 11, but a single-stage compression / single-stage expansion, or three or more stages, or even a combination of different numbers of stages for compression and expansion, is also applicable. Furthermore, while the number of compressors and expanders is one, there is no particular limitation and they may be two or more. Furthermore, the number of motors and compressors, and generators and expanders may also be different. Furthermore, in each of the embodiments, the compressors 6, 7 and the expanders 10, 11 are separate devices, but the compressor and expander (motor and generator) may be combined into one device.

[0103] For example, the CAES apparatus 1J shown in Fig. 11 shows a case where the two-stage CAES apparatus 1 shown in Fig. 1 has been changed to a single-stage configuration. During charging operation, compressed air compressed in a single stage by the compressor 6 exchanges heat with a heat storage medium in the heat exchanger 24 and is then stored in the accumulator tank 8 as low-temperature, high-pressure compressed air. The heat storage medium heated in the heat exchanger 24 is stored in the heat storage tank 21. During discharging operation, the heat storage medium flowing out of the heat storage tank 21 is heated by the radiator 34 of the heat pump unit 30 and then supplied to the heat exchanger 26. The compressed air supplied from the accumulator tank 8 to the expander 10 is heated by heat exchange with the heat storage medium in the heat exchanger 26 and then supplied to the expander 10.

[0104] The CAES apparatus 1J is also provided with a heat pump unit 30, which absorbs heat from the low-temperature heat storage medium discharged from the heat exchanger 26 and dissipates heat to the high-temperature heat storage medium flowing into the heat exchanger 26. This makes it possible to more efficiently recover the heat of compression stored in the heat storage medium and transfer it to the compressed air before expansion, thereby making it possible to raise the temperature of the compressed air supplied to the expander 10. As a result, it is possible to improve the power recovery efficiency and further improve the responsiveness to fluctuations in power demand.

[0105] The single-stage configuration on the charging side (motor 4, compressor 6, heat exchanger 24) and the single-stage configuration on the power generation side (heat exchanger 26, expander 10, generator 12) shown in Figure 11 can also be applied to each of the CAES devices in Figures 1 to 10.

[0106] According to each of the above-described embodiments, the following advantageous effects are achieved.

[0107] (C1) As shown in FIG. 11, a compressed air energy storage device (CAES device) 1J includes a compressor 6 driven by a motor (electric motor) 4 to compress air, a first heat exchanger 24 to heat a heat storage medium by heat exchange with the compressed air compressed by the compressor 6, a pressure storage tank 8 to store the compressed air after heat exchange in the heat exchanger 24, an expander 10 driven by the compressed air stored in the pressure storage tank 8, a generator 12 driven by the expander 10, a heat exchanger (second heat exchanger) 26 to heat the compressed air flowing into the expander 10 by heat exchange with the heat storage medium heated in the heat exchanger (first heat exchanger) 24, and a heat pump unit (heat pump device) 30 to absorb heat from the heat storage medium after heat exchange in the heat exchanger 26 and release the heat to the compressed air that drives the expander 10.

[0108] (C2) In the above (C1), as shown in Figures 1, 11, etc., the heat pump unit 30 may absorb heat from the heat storage medium after heat exchange in the heat exchangers 26, 27, and dissipate heat to the heat storage medium supplied to the heat exchangers 26, 27.

[0109] Regarding the above (C1) and (C2), for example, in the CAES apparatus 1J shown in FIG. 11, a heat pump unit 30 is used to absorb heat from a low-temperature heat storage medium discharged from a heat exchanger 26 that heats compressed air, and dissipate the heat to a high-temperature heat storage medium that is heated in the heat exchanger 24 and flows into the heat exchanger 26. That is, the heat energy absorbed from the low-temperature heat storage medium is dissipated to the compressed air that drives the expander 10 via the heat storage medium flowing into the heat exchanger 26. This allows the compression heat (thermal energy) stored in the heat storage medium to be more efficiently recovered and transferred to the compressed air before expansion. As a result, the heat storage medium flowing into the heat exchanger 26 has a higher temperature, and the compressed air supplied to the expander 10 can be heated to a higher temperature. That is, this improves the power recovery efficiency and further improves the responsiveness to fluctuations in power demand.

[0110] (C3) In (C1) above, as in the CAES apparatus 1A shown in FIG. 3, the heat pump unit 30 includes an evaporator (heat absorber) 35 through which a refrigerant circulates and radiators 34a and 34b, and the evaporator 35 absorbs heat from the heat storage medium after heat exchange in the heat exchanger 26, and the radiators 34a and 34b radiate the heat energy absorbed in the evaporator 35 to compressed air heated in the heat exchangers 26 and 27.

[0111] The compressed air heated by the heat exchanger 26 is further heated by the radiator 34a and supplied to the expander 10, and the compressed air heated by the heat exchanger 27 is further heated by the radiator 34b and supplied to the expander 11. In this way, in the CAES apparatus 1A shown in FIG. 3, the thermal energy absorbed from the low-temperature heat storage medium by the evaporator 35 is radiated by the radiators 34a and 34b to the compressed air heated by the heat exchangers 26 and 27. As a result, the compressed air driving the expanders 10 and 11 can be heated to a higher temperature, which increases the power generation and improves the power recovery efficiency. Furthermore, since the temperature of the compressed air can be raised to a higher temperature, the temperature of the compressed air before expansion is raised more quickly, thereby improving the responsiveness to fluctuations in power demand.

[0112] (C4) In the above (C3), as in the CAES apparatus 1B shown in FIG. 4, the heat exchangers (26a, 27a) are configured as three-fluid heat exchangers 26a, 27a into which the heat storage medium heated by the heat exchangers 24, 25, the refrigerant flowing out from the radiators 34a, 34b, and the compressed air supplied to the expanders 10, 11 flow. The heat storage medium, after dissipating heat to the compressed air in the radiators 34a, 34b, flows into the three-fluid heat exchangers 26a, 27a and dissipates heat to the compressed air. Therefore, the temperature of the refrigerant returning to the expansion valve 32 of the heat pump unit 30 is lower than in the configuration shown in FIG. 3. Therefore, the refrigerant temperature after adiabatic expansion can be lowered, and the heat absorption (heat recovery) from the heat storage medium to the refrigerant in the evaporator 35 can be increased. As a result, the heat recovery efficiency of the heat pump unit 30 is improved, power consumption can be reduced, and the power recovery efficiency of the CAES apparatus 1B can be improved.

[0113] (C5) In the above (C1), as shown in FIG. 6, the CAES apparatus 1D further includes an accumulator tank (main accumulator tank) 8b, 8c that stores compressed air after heat exchange in the heat exchangers (first heat exchangers) 24, 25, and an accumulator tank (auxiliary accumulator tank) 8a that is connected to the compressed air inlet side of the heat exchanger 25 and stores compressed air compressed in the compressors 6, 7. The heat exchangers (second heat exchangers) 26, 27 heat the compressed air flowing from the accumulator tanks 8b, 8c into the expanders 10, 11 by heat exchange with the heat storage medium heated in the heat exchangers 24, 25, drive the expanders 10, 11 with the compressed air stored in the accumulator tank 8a, and start the flow of the heat storage medium heated in the heat exchangers 24, 25 into the heat exchangers 26, 27. The CAES apparatus 1D is further provided with a control device 40 that drives the expanders 10, 11 with the compressed air stored in the accumulator tanks 8b, 8c.

[0114] For example, in the CAES apparatuses 1D to 1G shown in Figures 6 to 9, the heat pump unit 30 absorbs heat from the heat storage medium after heat exchange in the heat exchangers 26, 27, and radiates the heat to the compressed air supplied to the expanders 10, 11 by the radiator 34. Also, in the CAES apparatuses 1D to 1G shown in Figure 10, the heat pump unit 30 absorbs heat from the heat storage medium after heat exchange in the heat exchangers 26, 27, and radiates the heat to the heat storage medium supplied to the heat exchangers 26, 27 by the radiator 34. In other words, the thermal energy absorbed from the low-temperature side heat storage medium is radiated to the compressed air that drives the expanders 10, 11 via the heat storage medium flowing into the heat exchangers 26, 27.

[0115] As described above, the heat pump unit 30 absorbs heat from the heat storage medium after heat exchange in the heat exchangers 26, 27 and dissipates the heat to the compressed air that drives the expanders 10, 11. Therefore, the temperature of the compressed air supplied to the expanders 10, 11 can be made higher than before, thereby improving the power recovery efficiency and further improving the responsiveness.

[0116] In addition, after the expanders 10 and 11 are driven by the high-temperature, high-pressure compressed air stored in the pressure storage tank 8a, they are switched to being driven by the low-temperature, high-pressure compressed air from the pressure storage tanks 8b and 8c, so the expanders 10 and 11 can start up quickly as soon as the discharge operation begins, thereby improving responsiveness to fluctuations in power demand.

[0117] Furthermore, the expanders 10 and 11 are driven by the compressed air stored in the pressure accumulator tank 8a, and the heat storage medium heated in the heat exchanger 24 begins to flow into the heat exchangers 26 and 27, and then the expanders 10 and 11 are driven by the compressed air stored in the pressure accumulator tanks 8b and 8c.This makes it possible to prevent a decrease in generated power due to insufficient warm-up of the heat exchangers 26 and 27 when the compressed air supply source is switched from the pressure accumulator tank 8a to the pressure accumulator tanks 8b and 8c.

[0118] (C6) In (C5) above, the heat pump unit 30 absorbs heat from the heat storage medium after heat exchange in the heat exchangers 26 and 27 and dissipates the heat to at least one of the compressed air flowing from the accumulator tanks 8b and 8c into the expander 10 and the compressed air flowing from the accumulator tank 8a into the expander 10. For example, in the CAES apparatus 1D shown in FIG. 6, heat is dissipated from the accumulator tank 8a to the compressed air flowing into the expander 10, in the CAES apparatus 1E shown in FIG. 7, heat is dissipated to both the compressed air flowing from the accumulator tank 8a and the accumulator tanks 8b and 8c into the expander 10, and in the CAES apparatuses 1F and 1G shown in FIGS. 8 and 9, heat is dissipated from the accumulator tanks 8b and 8c to the compressed air flowing into the expander 10. Therefore, the temperature of the compressed air supplied to the expanders 10 and 11 can be made higher than before, thereby improving power recovery efficiency and further improving responsiveness.

[0119] (C7) In the above (C6), as shown in the CAES apparatus 1G in FIG. 9, the expanders 10 and 11 form a multi-stage expander, with the expander 10 being the first expansion stage and the expander 11 being the second expansion stage. The heat exchangers 26 and 27 are provided individually on the inflow sides of the expanders 10 and 11, respectively, and the heat pump unit 30 absorbs heat from the heat storage medium after heat exchange in the heat exchangers 26 and 27 and dissipates heat to the compressed air flowing from the pressure storage tanks 8b and 8c into the expander 10, and to the compressed air flowing from the expander 10 into the expander 11. Therefore, the amount of power generated by the generator 12 driven by the expander 10 and the amount of power generated by the generator 13 driven by the expander 11 increase, thereby improving the power recovery efficiency.

[0120] (C8) In the above (C5), as in the CAES apparatus 1H shown in Fig. 10, the heat pump unit 30 absorbs heat from the heat storage medium after heat exchange in the heat exchangers 26, 27 and dissipates heat to the heat storage medium supplied to the heat exchangers 26, 27. Therefore, the thermal energy absorbed from the heat storage medium after heat exchange in the heat exchangers 26, 27 is dissipated to the compressed air supplied to the expanders 10, 11 via the heat storage medium supplied to the heat exchangers 26, 27. As a result, the temperature of the compressed air supplied to the expanders 10, 11 can be made higher than before, thereby enabling improvement in power recovery efficiency and further improvement in responsiveness.

[0121] (C9) In the above (C1), the heat pump unit 30 may be a heat pump device that employs a vapor compression cycle using a refrigerant.

[0122] (C10) In the above (C1), pressurized water is used as the heat storage medium. Since pressurized water has a higher boiling point than non-pressurized water, the temperature of the heat storage medium can be raised to a higher level, and the compressed air can be heated to a higher temperature by the heat storage medium, thereby further improving the power recovery efficiency.

[0123] (C11) As shown in Figure 11, the heat pump unit 30 is a heat pump device used in a compressed air energy storage device that stores compressed air and heat of compression obtained by compressing air in a compressor 6, heats the compressed air by heat exchange between the compressed air and a heat storage medium that has absorbed the heat of compression in a heat exchanger 26, and generates electricity by driving an expander 10 with the heated compressed air, and is equipped with an evaporator 35 that absorbs heat from the heat storage medium after heat exchange in the heat exchanger 26, and a radiator 34 that radiates heat to the heat storage medium flowing into the heat exchanger 26. Therefore, the heat pump unit 30 can efficiently transfer thermal energy stored in the heat storage medium to the compressed air, and the power recovery efficiency in the compressed air energy storage device can be improved.

[0124] In each of the embodiments described above, renewable energy power generation may include any energy source that utilizes natural energy that is constantly or repeatedly replenished and irregularly fluctuates, such as wind power, sunlight, solar heat, wave or tidal power, flowing water or tides, and geothermal heat. Furthermore, power may fluctuate due to other large-power consuming devices in the factory. Furthermore, the grid power that supplies this power may not only be grid power, but also microgrid power in the region or within the factory.

[0125] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and the technical scope of the present invention is not intended to be limited to the specific configurations of the above embodiments. For example, in each of the above embodiments, a heat pump device employing a vapor compression cycle using a refrigerant is used as the heat pump unit 30, but an absorption heat pump device may also be used. Furthermore, it is also possible to combine the configurations described in the above different embodiments. [Explanation of symbols]

[0126] 1, 1A to 1H, 1J...Compressed air energy storage device (CAES device), 2A...Compressor unit, 2B...Expander unit, 3...Grid power, 4, 5...Motor (electric motor), 6, 7...Compressor, 8, 8a, 8b, 8c...Accumulator tank, 9...Inverter device, 10, 11...Expander, 12, 13...Generator, 14...Power conditioner, 20...Heat storage unit, 21, 22...Heat storage tank, 24 to 27...Heat exchanger, 26a, 27a...Three-fluid heat exchanger, 28, 29...Transfer pump, 30...Heat pump unit, 31...Refrigerant compressor, 32...Expansion valve, 34, 34a, 34b...Radiator, 35...Evaporator, 40...Control device

Claims

1. a compressor driven by an electric motor to compress air; a first heat exchanger that heats a heat storage medium by heat exchange with compressed air compressed by the compressor; an accumulator tank that stores the compressed air after heat exchange in the first heat exchanger; an expander driven by the compressed air stored in the accumulator tank; a generator driven by the expander; a second heat exchanger that heats the compressed air flowing into the expander by heat exchange with the heat storage medium heated in the first heat exchanger; a heat pump device for absorbing heat from the heat storage medium after heat exchange in the second heat exchanger and releasing the heat to compressed air that drives the expander; A compressed air energy storage device comprising:

2. 2. The compressed air energy storage device of claim 1, The heat pump device absorbs heat from the heat storage medium after heat exchange in the second heat exchanger and dissipates heat to the heat storage medium supplied to the second heat exchanger. Compressed air energy storage device.

3. 2. The compressed air energy storage device of claim 1, The heat pump device includes a heat absorber and a heat radiator through which a refrigerant flows, the heat absorber absorbs heat from the heat storage medium after heat exchange in the second heat exchanger, The heat radiator radiates the heat energy absorbed by the heat absorber to the compressed air heated by the second heat exchanger. Compressed air energy storage device.

4. 4. The compressed air energy storage device according to claim 3, The second heat exchanger is a three-fluid heat exchanger into which the heat storage medium heated in the first heat exchanger, the refrigerant flowing out from the radiator, and the compressed air supplied to the expander flow, Compressed air energy storage device.

5. 2. The compressed air energy storage device of claim 1, a main accumulator tank that is the accumulator tank that stores the compressed air after heat exchange in the first heat exchanger, and a sub-accumulator tank that is connected to the compressed air inlet side of the first heat exchanger and stores the compressed air compressed by the compressor; a control device, the second heat exchanger heats the compressed air flowing from the main accumulator tank into the expander by heat exchange with the heat storage medium heated in the first heat exchanger; The control device driving the expander with compressed air stored in the auxiliary pressure accumulator tank to start flowing the heat storage medium heated in the first heat exchanger into the second heat exchanger; The expander is driven by the compressed air stored in the auxiliary pressure accumulator tank, and then the expander is driven by the compressed air stored in the main pressure accumulator tank. Compressed air energy storage device.

6. 6. The compressed air energy storage device according to claim 5, The heat pump device is Heat is absorbed from the heat storage medium after heat exchange in the second heat exchanger, heat is dissipated to the compressed air flowing from the main pressure accumulator tank to the expander or to the compressed air flowing from the sub pressure accumulator tank to the expander; Compressed air energy storage device.

7. 7. The compressed air energy storage device according to claim 6, The expander is a multi-stage expander having a first expansion stage and a second expansion stage, the second heat exchanger is provided individually on the inlet side of each of the first expansion stage and the second expansion stage, the heat pump device absorbs heat from the heat storage medium after heat exchange in the second heat exchanger, and dissipates heat to the compressed air flowing from the main pressure accumulator tank into the first expansion stage and to the compressed air flowing from the first expansion stage into the second expansion stage. Compressed air energy storage device.

8. 6. The compressed air energy storage device according to claim 5, The heat pump device is Heat is absorbed from the heat storage medium after heat exchange in the second heat exchanger, The heat is dissipated to the heat storage medium supplied to the second heat exchanger. Compressed air energy storage device.

9. 2. The compressed air energy storage device of claim 1, The heat pump device is a heat pump device that employs a vapor compression cycle using a refrigerant. Compressed air energy storage device.

10. 2. The compressed air energy storage device of claim 1, The heat storage medium is pressurized water. Compressed air energy storage device.

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