Patent Publication Number: US-2022220894-A1

Title: Compressed air energy storage power generation device

Description:
TECHNICAL FIELD 
     The present invention relates to a compressed air energy storage power generation device. 
     BACKGROUND ART 
     As one of the techniques for smoothing or leveling fluctuating unstable power generation outputs, compressed air energy storage (CAES) is known. In a compressed air energy storage power generation device using this technique, surplus power, occurring when the power generated by a generator is surplus, is supplied to an electric motor. Then, a compressor is driven by the electric motor to generate compressed air. The generated compressed air is temporarily stored. Then, the generator is driven when necessary by operating an expander (turbine) with the compressed air stored to reconvert into electricity. 
     Patent Document 1 describes an adiabatic compressed air energy storage (ACAES) power generation device that recovers heat from compressed air before the compressed air is stored and reheats the stored compressed air when it is supplied to a turbine. Since the ACAES power generation device recovers compression heat to use it when power is generated, it has higher power generation efficiency than a normal CAES power generation device. Hereinafter, the ACAES power generation device and the CAES power generation device are also simply referred to as a CAES power generation device without distinguishing them from each other. 
     PRIOR ART DOCUMENT 
     Patent Document 
     Patent Document 1: JP 2013-509530 A 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     In the CAES power generation device of Patent Document 1, a compressor and an expander are separately configured, so that the entire device is increased in size and cost. 
     An object of the present invention is to reduce the size and cost of a CAES power generation device by integrating a compressor and an expander. 
     Means for Solving the Problems 
     According to a first aspect of the present invention, there is provided a compressed air energy storage power generation device including: a compressor/expander combined machine that is of displacement type and has a function as a compressor for compressing air and a function as an expander for expanding compressed air; a motor/generator combined machine that is mechanically connected to the compressor/expander combined machine and has a function as an electric motor for driving the compressor/expander combined machine and a function as a generator driven by the compressor/expander combined machine; and a pressure accumulator that is fluidly connected to the compressor/expander combined machine and stores compressed air generated by the compressor/expander combined machine. 
     According to this configuration, the compressor/expander combined machine in which a compressor and an expander are integrated is used in the compressed air energy storage power generation device, so that the entire device can be reduced in size. In addition, the number of parts to be maintained can be reduced, so that maintenance cost can be reduced. Cost for various construction including piping construction can be reduced, and an installation space can be reduced. Therefore, cost can be reduced. 
     The compressor/expander combined machine includes a first casing that defines a compression chamber and is provided with a first through hole, a first rotating shaft member that is inserted through the first through hole, and a first seal part that seals a gap between the first rotating shaft member and the first casing in the first through hole, in which the first seal part may include a lubricant labyrinth seal having a rotationally axisymmetric shape so as not to depend on a rotation direction of the first rotating shaft member. 
     According to this configuration, a fluid other than air, such as a lubricant, existing outside the compression chamber, can be suppressed from entering the compression chamber in the compressor/expander combined machine. In the compressor/expander combined machine, the first rotating shaft member rotates in both directions, not in one direction. That is, a direction in which the first rotating shaft member rotates when the compressor/expander combined machine functions as a compressor is different from a direction in which the first rotating shaft member rotates when the compressor/expander combined machine functions as an expander. When these functions are switched, the first rotating shaft member is reversed. Therefore, a shaft seal structure of the compressor/expander combined machine is required to be designed to not depend on the rotation direction. If a first seal part of a screw groove type (i.e., a spiral type) depending on the rotation direction is provided, an airflow going from the outside of the compression chamber toward the compression chamber may be caused in the first through hole depending on the rotation direction. In the above configuration, a lubricant labyrinth seal having a rotationally axisymmetric shape is adopted as the first seal part so as not to depend on the rotation direction of the first rotating shaft member, so that occurrence of the airflow can be suppressed. 
     The first seal part further includes an air ring seal disposed, in a direction in which the first rotating shaft member extends, closer to the compression chamber than the lubricant labyrinth seal. The compressor/expander combined machine may further include: a first inlet that is provided in the first casing and introduces compressed air into the lubricant labyrinth seal; and a first air source that is fluidly connected to the first inlet and supplies compressed air to the lubricant labyrinth seal from the compression chamber side via the first inlet. 
     According to this configuration, the lubricant labyrinth seal using the compressed air supplied from the first air source via the first inlet can suppress the lubricant entering the compression chamber, so that a sealing property can be enhanced without depending on the rotation direction of the first rotating shaft member. In addition, two or more of the air ring seals can suppress the compressed air introduced from the first air source via the first inlet from entering the compression chamber, so that the sealing property can be further enhanced. 
     The motor/generator combined machine includes a second casing that defines a coil chamber and is provided with a second through hole, a second rotating shaft member that is inserted through the second through hole, and a second seal part that seals a gap between the second rotating shaft member and the second casing in the second through hole, in which the second seal part may have a rotationally axisymmetric shape so as not to depend on a rotation direction of the second rotating shaft member. 
     According to this configuration, a fluid other than air, such as a lubricant, existing outside the coil chamber, can be suppressed from entering the coil chamber in the motor/generator combined machine. In the motor/generator combined machine, the second rotating shaft member rotates in both directions, not in one direction. That is, a direction in which the second rotating shaft member rotates when the motor/generator combined machine functions as an electric motor is different from a direction in which the second rotating shaft member rotates when the motor/generator combined machine functions as a generator. When these functions are switched, the second rotating shaft member is reversed. Therefore, a shaft seal structure of the motor/generator combined machine is required to be designed to not depend on the rotation direction. If a second seal part of a screw groove type (i.e., a spiral type) depending on the rotation direction is provided, an airflow going from the outside of the coil chamber toward the coil chamber may be caused in the second through hole depending on the rotation direction. In the above configuration, a rotationally axisymmetric shape is adopted as the second seal part so as not to depend on the rotation direction of the second rotating shaft member, so that occurrence of the airflow can be suppressed. 
     The motor/generator combined machine may further include a second inlet that is provided in the second casing and introduces compressed air into the coil chamber, and a second air source that is fluidly connected to the second inlet and supplies compressed air into the coil chamber from the second inlet. 
     According to this configuration, the pressure of the coil chamber can be increased by supplying compressed air to the coil chamber from the second air source via the second inlet. Since the coil chamber has a higher pressure than the surroundings, a fluid other than air, such as a lubricant, can be suppressed from entering the coil chamber. 
     The compressed air energy storage power generation device may further include: an inflow path having a check valve that is disposed to allow air to flow only in an inflow direction into the compressor/expander combined machine; and a discharge path having a check valve that is disposed to allow air to flow only in a discharge direction from the compressor/expander combined machine. 
     According to this configuration, the flow directions of air can be mechanically switched without performing electromagnetic control. In the compressor/expander combined machine, the flow directions of air are opposite between when it operates as a compressor and when it operates as an expander. If an electromagnetic control part, such as a three-way solenoid valve, capable of switching flow directions, is used, the flow directions can be switched by electromagnetic control, but a structure and associated control become complicated. On the other hand, in the above configuration, mechanical simple switching of the flow directions of air that does not require electromagnetic control is realized by providing two routes (inflow path, discharge path) in each of which an inflow direction is defined. 
     The compressed air energy storage power generation device may further include: a heat exchange part that is disposed on a high-pressure side of the compressor/expander combined machine and has a function of exchanging heat between the compressed air generated by the compressor/expander combined machine and a heat medium to heat the heat medium and cool the compressed air, and a function of exchanging heat between the compressed air supplied to the compressor/expander combined machine and the heat medium to cool the heat medium and heat the compressed air; a high-temperature heat storage part that is fluidly connected to the heat exchange part and stores the heat medium heated by the heat exchange part; a low-temperature heat storage part that is fluidly connected to the heat exchange part and stores the heat medium cooled by the heat exchange part; and a pressure equalizing part that equalizes pressures of the high-temperature heat storage part and the low-temperature heat storage part. 
     According to this configuration, heat can be recovered from the compressed air, heated by the compression heat during compression, by the heat medium in the heat exchange part, and the heat can be stored in the high-temperature heat storage part as thermal energy. When the high-temperature heat medium stored in the high-temperature heat storage part supplies heat to the heat exchange part during expansion, the heat is given from the heat medium to the compressed air before expansion, which enables expansion efficiency to be improved. 
     The heat medium is water, and the pressure equalizing part may include a flow path that fluidly connects the high-temperature heat storage part and the low-temperature heat storage part, and an inert gas source that is fluidly connected to the high-temperature heat storage part and the low-temperature heat storage part and supplies an inert gas at a predetermined pressure to the high-temperature heat storage part and the low-temperature heat storage part. 
     According to this configuration, the flow of the heat medium can be stabilized by equalizing the pressures of the heat media in the high-temperature heat storage part and the low-temperature heat storage part. In particular, water is used as the heat medium, so that a compressed air energy storage power generation device excellent in environmental properties can be manufactured at low cost. However, when the heat medium is water, the heat medium boils at 100° C. or higher under atmospheric pressure, so that in order to suppress the boiling of the water, an inert gas at a predetermined pressure is supplied from the inert gas source. That is, the predetermined pressure here indicates a degree of pressure that can suppress boiling of water. 
     The compressor/expander combined machine may further include a pinion that is for transmitting rotational driving force with the motor/generator combined machine, and an anti-loosening nut that holds the pinion so as not to loosen. 
     According to this configuration, the pinion can be suppressed from loosening by the anti-loosening nut. The anti-loosening nut has a function of not loosening by a wedge effect even when the first rotating shaft member rotates forward and backward. 
     The compressor/expander combined machine may further include a pinion that is for transmitting rotational driving force with the motor/generator combined machine, a plurality of bolts that hold the pinion, pressing lids that press the plurality of bolts, and an anti-loosening nut that fixes the pressing lid. 
     According to this configuration, the pressing lids for pressing the plurality of bolt are fixed by the anti-loosening nut, so that the pressing lids can be suppressed from loosening and the plurality of bolts can be suppressed from loosening. Therefore, the pinion can be suppressed from loosening. 
     Effects of the Invention 
     According to the present invention, a compressor/expander combined machine in which a compressor and an expander are integrated is used in a compressed air energy storage power generation device, so that the entire device can be reduced in size and reduced in cost. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic configuration view of a compressed air energy storage power generation device according to a first embodiment of the present invention; 
         FIG. 2  is a front view of a compressor/expander combined machine; 
         FIG. 3  is a partial cross-sectional view of a vicinity of a bearing, taken along line III-III of  FIG. 2 ; 
         FIG. 4  is a partial cross-sectional view of the vicinity of the bearing, taken along line IV-IV of  FIG. 2 ; 
         FIG. 5  is a cross-sectional view illustrating a shaft seal structure of a motor/generator combined machine; 
         FIG. 6  is a front view of a compressor/expander combined machine of a compressed air energy storage power generation device according to a second embodiment; 
         FIG. 7  is a cross-sectional view taken along line VII-VII of  FIG. 6 ; 
         FIG. 8  is a perspective view of a pinion portion of  FIG. 7 ; 
         FIG. 9  is an exploded perspective view of the pinion portion of  FIG. 7 ; and 
         FIG. 10  is an enlarged view of a hexagon socket head bolt portion of  FIG. 7 . 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. 
     First Embodiment 
     With reference to  FIG. 1 , a compressed air energy storage (CAES) power generation device  1  supplies power to a power system  3  by leveling output fluctuations of a power generation facility  2  that generates power by using renewable energy, and supplies power corresponding to fluctuations in power demand to the power system  3 . 
     In the present embodiment, the power generation facility  2  that generates power by using renewable energy is exemplified by a wind power generation facility. However, the type of the renewable energy is not limited to this, and all of power generation, using energy that is steadily or repeatedly replenished by natural force and fluctuates irregularly, such as sunlight, solar heat, wave force, tidal force, flowing water, or tide, can be targeted. Furthermore, in addition to the renewable energy, all of what fluctuate in amount of power generation, such as a factory having a power generation facility that operates irregularly, can be targeted. 
     The CAES power generation device  1  of the present embodiment includes an air flow path system  10 , a heat medium flow path system  20 , and an inert gas flow path system  30 . 
     (Air Flow Path System) 
     The air flow path system  10  is provided with a compressor/expander combined machine  11 , a heat exchanger (heat exchange part)  12 , and a pressure accumulation tank (pressure accumulator)  13 . The air flow path system  10  includes air flow paths  10   a  to  10   g.    
     A motor/generator combined machine  14  is mechanically connected to the compressor/expander combined machine  11 . The motor/generator combined machine  14  has a function as an electric motor that drives the compressor/expander combined machine  11  and a function as a generator that is driven by the compressor/expander combined machine  11 . The power generation facility  2  is electrically connected to the motor/generator combined machine  14 . The motor/generator combined machine  14  is driven by fluctuating input power from the power generation facility  2 . In addition, the motor/generator combined machine  14  is electrically connected to the power system  3 . The power generated by the motor/generator combined machine  14  can be transmitted to the power system  3 . Details of the structure of the motor/generator combined machine  14  will be described later. 
     The air flow path  10   a  is fluidly connected to a low-pressure port  11   a  of the compressor/expander combined machine  11 . The air flow path  10   a  is branched into the air flow path (inflow path)  10   b  for intake and the air flow path (outflow path)  10   c  for exhaust. The ends of the air flow paths  10   b  and  10   c  are open to the atmosphere. The air flow path  10   b  is provided with a silencer  15  that reduces intake sound, and a check valve  16   a  that allows air to flow only in an intake direction (an inflow direction into the low-pressure port  11   a  of the compressor/expander combined machine  11 ) and blocks air in the opposite direction. The air flow path is provided with a check valve  16   b  that allows air to flow only in an exhaust direction (a discharge direction from the low-pressure port  11   a  of the compressor/expander combined machine  11 ) and blocks air in the opposite direction. 
     The air flow path  10   d  is fluidly connected to a high-pressure port  11   b  of the compressor/expander combined machine  11 . The air flow path  10   d  is branched into the air flow path (inflow path)  10   e  to which compressed air is supplied from a pressure accumulation tank  13  and the air flow path (outflow path)  10   f  for supplying compressed air to the pressure accumulation tank  13 . They are joined at the air flow path  10   g . The air flow path  10   g  is fluidly connected to the pressure accumulation tank  13 . The air flow path  10   e  is provided with a check valve  16   c  that allows air to flow only in an air supply direction to the compressor/expander combined machine  11  (an inflow direction to the high-pressure port  11   b  of the compressor/expander combined machine  11 ) and blocks air in the opposite direction. The air flow path  10   f  is provided with a check valve  16   d  that allows a flow in a pressure feeding direction to the pressure accumulation tank  13  (a discharge direction from the high-pressure port  11   b  of the compressor/expander combined machine  11 ) and blocks a flow in the opposite direction. 
     The compressor/expander combined machine  11  of the present embodiment is a screw type. Since the compressor/expander combined machine  11  of a screw type is speed controllable, it can follow irregularly-fluctuating input power from the power generation facility  2  with good responsiveness. Therefore, it is preferable as a constituent of the CAES power generation device  1 . However, the compressor/expander combined machine  11  only needs to be of a displacement type, and may be, for example, a scroll type or a reciprocating type in addition to the screw type. In addition, the compressor/expander combined machine  11  may be a single-stage type or a multi-stage type. Details of the structure of the compressor/expander combined machine  11  will be described later. 
     The pressure accumulation tank  13  can store compressed air and accumulate it as energy. The pressure accumulation tank  13  can be, for example, a tank made of steel. The number of the pressure accumulation tanks  13  is not particularly limited, and a plurality of them may be provided. In addition, the pressure accumulation tank  13  may not necessarily be in the form of a tank. Alternatively, it only needs to be in a form that can store compressed air, such as an underground cavity. 
     A heat exchanger  12  is interposed in the air flow path  10   d  fluidly connected to the high-pressure port  11   b  of the compressor/expander combined machine  11 . Details of the heat exchange in the heat exchanger  12  will be described later. 
     (Heat Medium Flow Path System) 
     The heat medium flow path system  20  is provided with the heat exchanger  12 , a high-temperature heat medium tank (high-temperature heat storage part)  21 , and a low-temperature heat medium tank (low-temperature heat storage part)  22 . The heat medium flow path system  20  includes heat medium flow paths  20   a  and  20   b . A pump  23   a  is disposed in the heat medium flow path  20   a , the pump  23   a  allowing the heat medium to flow between the heat exchanger  12  and the high-temperature heat medium tank  21 . Similarly, a pump  23   b  is disposed in the heat medium flow path  20   b , the pump  23   b  allowing the heat medium to flow between the heat exchanger and the low-temperature heat medium tank  22 . In the present embodiment, water is used as the heat medium. The type of the heat medium is not particularly limited, and for example, a mineral oil-based, glycol-based, or synthetic oil-based heat medium may be used. 
     Inside the high-temperature heat medium tank  21 , there are a portion (liquid phase part  21   a ) in which the heat medium is stored and a gas phase part  21   b  in which the heat medium is not stored and which is filled with N2 gas (inert gas). Similarly, inside the low-temperature heat medium tank  22 , there are a liquid phase part  22   a  in which the heat medium is stored and a gas phase part  22   b  filled with N2 gas. 
     In the heat exchanger  12 , the compressed air generated by the compressor/expander combined machine  11  and the heat medium from the low-temperature heat medium tank  22  exchange heat with each other, so that the heat medium is heated and the compressed air is cooled. In addition, in the heat exchanger  12 , the compressed air supplied to the compressor/expander combined machine  11  and the heat medium from the high-temperature heat medium tank  21  exchange heat with each other, so that the heat medium is cooled and the compressed air is heated. 
     The high-temperature heat medium tank  21  is a tank made of, for example, steel, and is preferably insulated from the outside. The high-temperature heat medium tank  21  stores the heat medium heated by the heat exchanger  12 . Therefore, the heat medium in the high-temperature heat medium tank  21  and the heat medium flow path  20   a  is at a high temperature in the heat medium flow path system  20 . In the high-temperature heat medium tank  21 , a temperature sensor  21   c  for measuring the temperature of the internal liquid phase part  21   a  and a pressure sensor  21   d  for measuring the pressure of the internal gas phase part  21   b  are installed. 
     The low-temperature heat medium tank  22  is a tank made of, for example, steel. The low-temperature heat medium tank  22  stores the heat medium cooled by the heat exchanger  12 . Therefore, the heat medium in the low-temperature heat medium tank  22  and the heat medium flow path  20   b  is at a low temperature in the heat medium flow path system  20 . In the low-temperature heat medium tank  22 , a temperature sensor  22   c  for measuring the temperature of the internal liquid phase part  22   a  is installed. Note that the pressure of the gas phase part  22   b  of the low-temperature heat medium tank  22  matches the pressure of the gas phase part  21   b  of the high-temperature heat medium tank  21 , as described later. 
     (Inert Gas Flow Path System) 
     The inert gas flow path system  30  includes the gas phase part  21   b  of the high-temperature heat medium tank  21 , the gas phase part  22   b  of the low-temperature heat medium tank  22 , and an N2 cylinder (inert gas source)  31 . The inert gas flow path system  30  includes inert gas flow paths  30   a  and  30   b.    
     The inert gas flow path  30   a  is a flow path that fluidly connects the gas phase part  21   b  of the high-temperature heat medium tank  21  and the gas phase part  22   b  of the low-temperature heat medium tank  22  so as to equalize the pressures. The inert gas flow path  30   b  extending to the N2 cylinder  31  is fluidly connected to the inert gas flow path  30   a . The inert gas flow path system  30  is filled with N2 gas supplied from the N2 cylinder  31 . Note that in the present embodiment, N2 gas is used as the inert gas, but the type of the inert gas is not limited thereto, and for example, Ar gas may be used. 
     In the present embodiment, the inert gas flow paths  30   a  and  30   b  and the N2 cylinder  31  constitute a pressure equalizing part of the present invention. The pressure equalizing part equalizes the pressures of the high-temperature heat medium tank  21  and the low-temperature heat medium tank  22 . 
     The pressure of the N2 gas supplied from the N2 cylinder  31  can be adjusted by a pressure regulating valve  32  interposed in the inert gas flow path  30   b . The aperture of the pressure regulating valve  32  is controlled by a controller  40 . 
     The controller  40  can be built by hardware including a central processing unit (CPU) and storage devices such as a random access memory (RAM) and a read only memory (ROM), and by software mounted on the hardware. 
     Based on the pressure value measured by the pressure sensor  21   d  and the temperature values measured by the temperature sensors  21   c  and  22   c , the controller  40  controls the pressure regulating valve  32  to regulate pressure such that the heat media in the high-temperature heat medium tank and the low-temperature heat medium tank  22  do not vaporize, that is, water does not boil in the present embodiment. 
     (Structure of Compressor/Expander Combined Machine) 
     With reference to  FIGS. 2 to 4 , the compressor/expander combined machine  11  includes a casing (first casing)  11   d  that defines a compression chamber R 1  and is provided with a through hole (first through hole)  11   c . In the compression chamber R 1 , a pair of male and female screw rotors  11   e  are disposed. The screw rotor  11   e  is supported by a rotating shaft member (first rotating shaft member)  11   f . The rotating shaft member  11   f  extends, through the through hole  11   c , from the inside to the outside of the casing  11   d . In the through hole  11   c , four air ring seals high (first seal parts) for sealing a gap between the rotating shaft member  11   f  and the casing  11   d  and one lubricant labyrinth seal (first seal part)  11   g   2  are disposed. 
     The air ring seals high are disposed, in a direction in which the rotating shaft member  11   f  extends, closer to the compression chamber R 1  than the lubricant labyrinth seal  11   g   2 . The four air ring seals high are floating seals that are biased, by weak wave springs  11   n   1 , in the direction in which the rotating shaft member  11   f  extends while maintaining a minimum gap with the rotating shaft member  11   f  and the positions of which are held by being pressed against fixed parts. The fixed parts against which the air ring seals high are pressed are the casing  11   d  or a plurality of spacers  11   n   2  disposed to fill gaps between the casing  11   d  and the air ring seals high. The air ring seal high is a component that exerts a sealing function using the pressure of air by holding the minimum gap with the rotating shaft member  11   f.    
     The lubricant labyrinth seal  11   g   2  has a rotationally axisymmetric shape so as not to depend on the rotation direction of the rotating shaft member  11   f . In other words, a screw seal of a spiral groove type, depending on the rotation direction of the rotating shaft member  11   f , is not adopted as the lubricant labyrinth seal  11   g   2 . The lubricant labyrinth seal  11   g   2  may be what has, for example, straight grooves, as illustrated in  FIG. 3 . Note that the structure on the low-pressure port  11   a  (see  FIG. 1 ) side is only illustrated in  FIG. 3 , but the structure on the high-pressure port  11   b  (see  FIG. 1 ) side is also substantially the same. 
     With reference to  FIGS. 3 and 4 , a bearing  11   h  is disposed, in the direction in which the rotating shaft member  11   f  extends, next to the lubricant labyrinth seal  11   g   2  (on the opposite side to the compression chamber R 1 ). The bearing  11   h  rotatably supports the rotating shaft member  11   f . A pinion  11   i  is disposed next to the bearing  11   h  (on the opposite side to the compression chamber R 1 ). The pinion  11   i  is rotatably held by an anti-loosening nut  11   j  so as not to loosen from the rotating shaft member  11   f  that supports the male screw rotor  11   e . The anti-loosening nut  11   j  is a nut whose loosening is suppressed by a wedge effect, and a publicly known anti-loosening nut can be used. Note that in the present embodiment, substantially the same structure is adopted also for the rotating shaft member  11   f  that supports the female screw rotor  11   e  except for the presence or absence of the pinion  11   i.    
     The casing  11   d  is provided with a vent  11   k   1  fluidly connected to a space between the third and fourth seals (counted from the compression chamber R 1  side) of the air ring seals  11   g   1 , and an inlet (first inlet)  11   k   2  for introducing compressed air into the air ring seals  11   g   1  and the lubricant labyrinth seal  11   g   2 . The vent  11   k   1  is open to the atmosphere. The inlet  11   k   2  is fluidly connected to a space between the air ring seals  11   g   1  and the lubricant labyrinth seal  11   g   2 . An air source (first air source)  111  is fluidly connected to the inlet  11   k   2 , and compressed air is supplied to the lubricant labyrinth seal  11   g   2  from the compression chamber R 1  via the inlet  11   k   2 . The air source  111  supplies compressed air of, for example, about 10 KPaG. 
     The flow of air in the air ring seals  11   g   1  can change depending on the operation of the compressor/expander combined machine  11 . Details of the flow of air in the air ring seals  11   g   1  are as follows. 
     When the compressor/expander combined machine  11  operates as a compressor and performs normal load operation, the low-pressure port  11   a  (see  FIG. 1 ) has a slightly negative or positive pressure. Therefore, in the air ring seals  11   g   1 , air tends to flow from the compression chamber R 1  toward the bearing  11   h  (right direction in  FIG. 3 ). Since the vent  11   k   1  is open to the atmosphere, the air tending to flow from the compression chamber R 1  toward the bearing  11   h  passes through the three air ring seals  11   g   1 , and is discharged into the atmosphere from the vent  11   k   1 . When passing through the air ring seals  11   g   1 , the air flows through the minimum gap between the air ring seals  11   g   1  and the rotating shaft member  11   f . A part of the compressed air introduced from the inlet  11   k   2  flows from the inlet  11   k   2  toward the bearing  11   h , and a part thereof passes through the fourth air ring seal high to be discharged from the vent  11   k   1 . In this way, the flow of air from the compression chamber R 1  toward the bearing  11   h  is generated, so that a lubricant that has lubricated the bearing  11   h  and the like is prevented from flowing into the compression chamber R 1  beyond the lubricant labyrinth seal  11   g   2  and the air ring seals high. 
     When the compressor/expander combined machine  11  operates as a compressor and performs no-load operation, the low-pressure port  11   a  (see  FIG. 1 ) has a negative pressure. Therefore, in the air ring seals high, air tends to flow from the bearing  11   h  toward the compression chamber R 1  (left direction in  FIG. 3 ). Since the vent  11   k   1  is open to the atmosphere, air flows in from the vent  11   k   1 , passes through the space between the third and fourth seals of the air ring seals  11   g   1 , and flows into the compression chamber R 1 . In addition, a part of the compressed air introduced from the inlet  11   k   2  flows toward the bearing  11   h , and a part thereof tends to flow toward the vent  11   k   1 . Therefore, in the vent  11   k   1 , air flows in or is discharged according to the pressure of the low-pressure port  11   a  and the pressure of the compressed air introduced from the inlet  11   k   2 . In either case, a part of the compressed air introduced from the inlet  11   k   2  flows toward the bearing  11   h , so that the lubricant that has lubricated the bearing  11   h  and the like is prevented from flowing into the compression chamber R 1  beyond the lubricant labyrinth seal  11   g   2  and the four air ring seals high. 
     When the compressor/expander combined machine  11  operates as an expander, the low-pressure port does not have a negative pressure. Therefore, the flow of air, generated when the compressor/expander combined machine  11  operates as an expander, is the same as the flow of air generated when the compressor/expander combined machine  11  operates as a compressor and performs normal load operation. 
     Note that the high-pressure port  11   b  (see  FIG. 1 ) does not have a negative pressure even when the compressor/expander combined machine  11  performs any of the operations described above. Therefore, the flow of air on the side of the non-illustrated high-pressure port  11   b  is the same as the flow of air on the side of the low-pressure port  11   a  when the compressor/expander combined machine  11  operates as a compressor and performs normal load operation. 
     The casing  11   d  is provided with an injection nozzle  11   m  capable of supplying a lubricant to the bearing  11   h . The lubricant injected from the injection nozzle  11   m  to the bearing  11   h  is blocked from flowing into the compression chamber R 1  by the lubricant labyrinth seal  11   g   2  and the air ring seals, so that it is discharged from a non-illustrated return hole to be returned to a non-illustrated lubricant tank. 
     In the casing  11   d , a cooling water flow path  11   o  (see  FIG. 4 ) is embedded. It is configured that the compression chamber R 1  can be cooled by allowing water at a low temperature to flow through the cooling water flow path  11   o . The flow rate of the water flowing through the cooling water flow path  11   o  is controlled by the controller  40  such that during compression operation (charging operation), a necessary amount of cold water is allowed to pass, and during expansion operation (power generation operation), the water supply is stopped or an extremely small amount of water is allowed to pass. 
     (Structure of Motor/Generator Combined Machine) 
     With reference to  FIG. 5 , the motor/generator combined machine  14  has a casing (second casing)  14   c  that defines a coil chamber R 2  and is provided with through holes (second through holes)  14   a  and  14   b . Note that in  FIG. 5 , an enlarged dashed circle portion is illustrated. A stator  14   d  and a rotor  14   e  are disposed in the coil chamber R 2 . The stator  14   d  is fixed to the inner surface of the casing  14   c . The rotor  14   e  is disposed inside the stator  14   d . The rotor  14   e  is supported by a rotating shaft member (second rotating shaft member)  14   f . The rotating shaft member  14   f  extends, through the through holes  14   a  and  14   b , from the inside to the outside of the casing  14   c . Lip seals (second seal parts)  14   g  and  14   h  each sealing a gap between the rotating shaft member  14   f  and the casing  14   c  are disposed in the through holes  14   a  and  14   b , respectively. 
     The lip seals  14   g  and  14   h  have a rotationally axisymmetric shape so as not to depend on the rotation direction of the rotating shaft member  14   f . In other words, a spiral groove type contact seal with inner screw grooves, depending on the rotation direction of the rotating shaft member  14   f , or a non-contact screw seal is not adopted as the lip seals  14   g  and  14   h . The lip seals  14   g  and  14   h  may be, for example, contact type seals without inner grooves that do not depend on the rotation direction of the rotating shaft member  14   f . Alternatively, labyrinth seals having straight grooves of a non-contact type, not depend on the rotation direction of the rotating shaft member  14   f , may be adopted. 
     Bearings  14   i  and  14   j  are disposed next to the lip seals  14   g  and  14   h , respectively. The bearings  14   i  and  14   j  rotatably support the rotating shaft member  14   f  on both sides of the bearings  14   i  and  14   j  by sandwiching the stator  14   d  and the rotor  14   e . A gear (not illustrated) is attached to the rotating shaft member  14   f  of the motor/generator combined machine  14 . This gear meshes with the pinion  11   i  attached to the rotating shaft member  14   f  of the compressor/expander combined machine  11 . Therefore, rotational driving force can be transmitted between the motor/generator combined machine  14  and the compressor/expander combined machine  11 . 
     The casing  14   c  is provided with an inlet (second inlet)  14   k  for introducing compressed air into the coil chamber R 2  and an outlet  141  for discharging compressed air from the coil chamber R 2 . An air source (second air source)  14   m  for supplying compressed air to the coil chamber R 2  from the inlet  14   k  is fluidly connected to the inlet  14   k . The air source  14   m  supplies air having a degree of pressure that can keep the coil chamber R 2  at a higher pressure than the surroundings. As a result, a lubricant or the like can be suppressed from flowing into the coil chamber R 2 . Therefore, in the present embodiment, an air seal is also adopted in the motor/generator combined machine  14 . 
     In the casing  14   c , a lubricant flow path  14   n  for supplying a lubricant to the bearings  14   i  and  14   j  is embedded. The lubricant flow path  14   n  is spirally routed in the casing  14   c  from an entrance  14   o  to an exit  14   p . As a result, the coil chamber R 2  can be cooled by allowing a lubricant at a low temperature to flow through the lubricant flow path. Such a cooling mechanism can exhibit constant cooling performance regardless of the rotational driving direction and rotation speed of the motor/generator combined machine  14 , so that it is particularly effective for the motor/generator combined machine  14 . In addition, the bearings  14   i  and  14   j  are disposed in the middle of the lubricant flow path  14   n , so that the bearings  14   i  and  14   j  can be lubricated. 
     (Operation and Effect) 
     With reference to  FIG. 1 , when the CAES power generation device  1  performs charging operation, the motor/generator combined machine  14  is driven as an electric motor (motor) by the fluctuating power input from the power generation facility  2 , and the compressor/expander combined machine  11  is driven as a compressor by the motor/generator combined machine  14 . The compressor/expander combined machine  11  sucks, from the low-pressure port  11   a , the air supplied via the air flow paths  10   a  and  10   b , and compresses the air to generate compressed air. The compressed air discharged from the high-pressure port  11   b  of the compressor/expander combined machine  11  passes through the air flow paths  10   d ,  10   f , and  10   g , and is pumped to the pressure accumulation tank  13  to be stored therein. That is, the pressure accumulation tank  13  stores the compressed air and accumulates it as energy. The compressed air passes through the heat exchanger  12  before being pumped to the pressure accumulation tank  13 . 
     During the charging operation, the heat medium at a low temperature stored in the low-temperature heat medium tank  22  is sent, by the pump  23   b , to the heat exchanger  12  after passing through the heat medium flow path  20   b . The high-temperature heat medium after the heat exchange in the heat exchanger  12  is sent, by the pump  23   a , to the high-temperature heat medium tank  21  after passing through the heat medium flow path  20   a.    
     The compressed air discharged from the high-pressure port  11   b  of the compressor/expander combined machine  11  is heated by the compression heat generated during compression. In the heat exchanger  12 , the compressed air is cooled and the heat medium is heated by heat exchange between the heat medium and the compressed air. Therefore, the compressed air cooled by the heat exchange in the heat exchanger  12  is stored in the pressure accumulation tank  13 . At this time, it is preferable that the compressed air is cooled to about normal temperature. In addition, the heat medium heated by the heat exchange in the heat exchanger  12  is stored in the high-temperature heat medium tank  21 . 
     When the CAES power generation device  1  performs the charging operation, the compressed air sent out from the pressure accumulation tank  13  is supplied to the high-pressure port  11   b  of the compressor/expander combined machine  11  after passing through the air flow paths  10   g ,  10   e , and  10   d . The compressed air passes through the heat exchanger  12  before being supplied to the compressor/expander combined machine  11 . The compressed air supplied to the high-pressure port  11   b  allows the compressor/expander combined machine  11  to operate as an expander, and the motor/generator combined machine  14  is driven as a generator. The power generated by the motor/generator combined machine  14  is supplied to the power system  3 . The air expanded by the compressor/expander combined machine  11  is exhausted from the low-pressure port  11   a  through the air flow paths  10   a  and  10   c.    
     During the power generation operation, the high-temperature heat medium stored in the high-temperature heat medium tank  21  is sent, by the pump  23   a , to the heat exchanger  12  after passing through the heat medium flow path  20   a . The heat medium at a low temperature, generated by the heat exchange in the heat exchanger  12 , is sent, by the pump  23   b , to the low-temperature heat medium tank  22  after passing through the heat medium flow path  20   b.    
     In the compressor/expander combined machine  11 , the temperature of the air drops due to heat absorption during expansion. Therefore, it is preferable that the compressed air supplied to the compressor/expander combined machine  11  has a high temperature. In the heat exchanger  12 , the compressed air is heated and the heat medium is cooled by the heat exchange between the heat medium and the compressed air. Therefore, the compressed air heated by the heat exchange in the heat exchanger  12  is supplied to the compressor/expander combined machine  11 . In addition, the heat medium cooled by the heat exchange in the heat exchanger  12  is stored in the low-temperature heat medium tank  22 . 
     According to the CAES power generation device  1  of the present embodiment, the compressor/expander combined machine  11  in which a compressor and an expander are integrated is used in the CAES power generation device  1 , so that the entire device can be reduced in size. In addition, the number of parts to be maintained can be reduced, so that maintenance cost can be reduced, cost for various construction including piping construction can be reduced, and an installation space can be reduced. Therefore, cost can be reduced. 
     In addition, the lubricant labyrinth seal  11   g   2  having a suitable shape as described above is adopted in the compressor/expander combined machine  11 , so that a fluid other than air, such as a lubricant, existing outside the compression chamber R 1 , can be suppressed from entering the compression chamber R 1 . In the compressor/expander combined machine  11 , the rotating shaft member  11   f  rotates in both directions, not in one direction. That is, a direction in which the rotating shaft member  11   f  rotates when the compressor/expander combined machine  11  functions as a compressor is different from a direction in which the rotating shaft member  11   f  rotates when the compressor/expander combined machine  11  functions as an expander. When these functions are switched, the rotating shaft member  11   f  is reversed. Therefore, the shaft seal structure of the compressor/expander combined machine  11  is required to be designed to not depend on the rotation direction. If a viscoseal of a screw groove type (i.e., a spiral type) depending on the rotation direction is provided, an airflow going from the outside of the compression chamber R 1  toward the compression chamber R 1  may be caused in the through hole  11   c  depending on the rotation direction. In the configuration of the present embodiment, the lubricant labyrinth seal  11   g   2  having a rotationally axisymmetric shape so as not to depend on the rotation direction of the rotating shaft member  11   f  is adopted, so that occurrence of the airflow can be suppressed. 
     In addition, the lubricant labyrinth seal  11   g   2  using the compressed air supplied to the compression chamber R 1  from the air source  111  via the inlet  11   k   2  can suppress a lubricant from entering the compression chamber R 2 , so that a sealing property can be enhanced without depending on the rotation direction of the rotating shaft member  11   f . In addition, two or more of the air ring seals high can suppress the compressed air introduced from the air source  111  via the inlet  11   k   2  from entering the compression chamber R 1 , so that the sealing property can be further enhanced. 
     In addition, the lip seals  14   g  and  14   h  having a suitable shape as described above are adopted in the motor/generator combined machine  14 , so that a fluid other than air, such as a lubricant, existing outside the coil chamber R 2 , can be suppressed from entering the coil chamber. In the motor/generator combined machine  14 , the rotating shaft member  14   f  rotates in both directions, not in one direction. That is, a direction in which the rotating shaft member  14   f  rotates when the motor/generator combined machine functions as an electric motor is different from a direction in which the rotating shaft member  14   f  rotates when the motor/generator combined machine  14  functions as a generator. When these functions are switched, the rotating shaft member  14   f  is reversed. Therefore, a shaft seal structure of the motor/generator combined machine  14  is required to be designed to not depend on the rotation direction. If a lip seal of a screw groove type (i.e., a spiral type) depending on the rotation direction is provided, an airflow going from the outside of the coil chamber R 2  toward the coil chamber R 2  may be caused in the through holes  14   a  and  14   b  depending on the rotation direction. In the configuration of the present embodiment, the lip seals  14   g  and  14   h  having a rotationally axisymmetric shape so as not to depend on the rotation direction of the rotating shaft member  14   f  are adopted, so that occurrence of the airflow can be suppressed. 
     In addition, the pressure of the coil chamber R 2  can be increased by supplying compressed air to the coil chamber R 2  from the air source  14   m  via the inlet  14   k . Since the coil chamber R 2  has a higher pressure than the surroundings, a fluid other than air, such as a lubricant, can be suppressed from entering the coil chamber R 2 . 
     In addition, the air flow paths  10   b ,  10   c ,  10   e , and  10   f  respectively having the check valves  16   a  to  16   d  are provided, so that the flow directions of air can be mechanically switched without performing electromagnetic control. The flow directions of air are opposite between when the compressor/expander combined machine  11  operates as a compressor and when it operates as an expander. If an electromagnetic control part, such as a three-way solenoid valve, capable of switching flow directions, is used, the flow directions can be switched by electromagnetic control, but a structure and associated control become complicated. On the other hand, in the configuration of the present embodiment, mechanical simple switching of the flow directions of air that does not require electromagnetic control is realized by providing two routes (air flow paths  10   b  and  10   c  or air flow paths  10   e  and  10   f ) in each of which an inflow direction is defined. 
     In addition, the heat medium flow path system  20  is provided, so that heat can be recovered from the compressed air, heated by the compression heat during compression, by the heat medium in the heat exchanger  12 , and the heat can be stored in the high-temperature heat medium tank  21  as thermal energy. When the high-temperature heat medium stored in the high-temperature heat medium tank  21  supplies heat to the heat exchange part during expansion, the heat is given from the heat medium to the compressed air before expansion, which enables expansion efficiency to be improved. 
     In addition, the pressures of the heat media in the high-temperature heat medium tank  21  and the low-temperature heat medium tank  22  are equalized, so that the flow of the heat medium can be stabilized. In particular, water is used as the heat medium, so that the CAES power generation device  1  excellent in environmental properties can be manufactured at low cost. However, when the heat medium is water, the water boils at 100° C. or higher under atmospheric pressure, so that in order to suppress the boiling of the water, N2 gas at a predetermined pressure is supplied from the N2 cylinder  31 . 
     In addition, the pinion  11   i  can be suppressed from loosening by the anti-loosening nut  11   j . The anti-loosening nut  11   j  has a function of not loosening by a wedge effect even when the rotating shaft member  11   f  rotates forward and backward. 
     Second Embodiment 
     A CAES power generation device  1  of the present embodiment illustrated in  FIGS. 6 to 10  is different from that of the first embodiment in a fixing method using an anti-loosening nut  11   j . Except for a configuration related thereto, other configurations are substantially the same as those of the CAES power generation device  1  of the first embodiment. Therefore, the same portions as the configurations described in the first embodiment are denoted by the same symbols, and description thereof will be omitted. 
     With reference to  FIGS. 6 to 10 , in the present embodiment, a pinion  11   i  is rotatably held by three hexagon socket head bolts (bolts)  11   p  via a fastener  11   r . The hexagon socket head bolt  11   p  is pressed from the outside by a pressing lid  11   q . The pressing lid  11   q  is fixed by the anti-loosening nut  11   j . Note that  FIG. 6  illustrates a state in which the pressing lids  11   q  and the anti-loosening nuts  11   j  are removed. 
     According to the present embodiment, the pressing lid  11   q  for pressing the hexagon socket head bolt  11   p  is fixed by the anti-loosening nut  11   j , so that the pressing lid  11   q  can be suppressed from loosening and the hexagon socket head bolt  11   p  can be suppressed from loosening. Therefore, the pinion  11   i  can be suppressed from loosening. 
     Although specific embodiments of the present invention have been described above, the present invention is not limited to the embodiments, and various modifications can be made within the scope of the present invention. In addition, the drawings are schematic, and dimensions and fine shapes may be different from those of actual ones. 
     DESCRIPTION OF SYMBOLS 
     
         
           1  Compressed air energy storage (CAES) power generation device 
           2  Power generation facility 
           3  Power system 
           10  Air flow path system 
           10   a ,  10   d ,  10   g  Air flow path 
           10   b ,  10   e  Air flow path (inflow path) 
           10   c ,  10   f  Air flow path (outflow path) 
           11  Compressor/expander combined machine 
           11   a  Low-pressure port 
           11   b  High-pressure port 
           11   c  Through hole (first through hole) 
           11   d  Casing (first casing) 
           11   e  Screw rotor 
           11   f  Rotating shaft member (first rotating shaft member) 
           11   g   1  Air ring seal (first seal part) 
           11   g   2  Lubricant labyrinth seal (first seal part) 
           11   h  Bearing 
           11   i  Pinion 
           11   j  Anti-loosening nut 
           11   k   1  Vent 
           11   k   2  Inlet (first inlet) 
           11   l  Air source (first air source) 
           11   m  Injection nozzle 
           11   n   1  Wave spring 
           11   n   2  Spacer 
           11   o  Cooling water flow path 
           11   p  Hexagon socket head bolt 
           11   q  Pressing lid 
           11   r  Fastener 
           12  Heat exchanger (heat exchange part) 
           13  Pressure accumulation tank (pressure accumulator) 
           14  Motor/generator combined machine 
           14   a ,  14   b  Through hole (second through hole) 
           14   c  Casing (second casing) 
           14   d  Stator 
           14   e  Rotor 
           14   f  Rotating shaft member (second rotating shaft member) 
           14   g ,  14   h  Lip seal (second seal part) 
           14   i ,  14   j  Bearing 
           14   k  Inlet (second inlet) 
           14   l  Outlet 
           14   m  Air source (second air source) 
           14   n  Lubricant flow path 
           14   o  Entrance 
           14   p  Exit 
           15  Silencer 
           16   a  to  16   d  Check valve 
           20  Heat medium flow path system 
           20   a ,  20   b  Heat medium flow path 
           21  High-temperature heat medium tank (high-temperature heat storage part) 
           21   a  Liquid phase part 
           21   b  Gas phase part 
           21   c  Temperature sensor 
           21   d  Pressure sensor 
           22  Low-temperature heat medium tank (low-temperature heat storage part) 
           22   a  Liquid phase part 
           22   b  Gas phase part 
           22   c  Temperature sensor 
           23   a ,  23   b  Pump 
           30  Inert gas flow path system 
           30   a ,  30   b  Inert gas flow path 
           31  N2 cylinder (inert gas source) 
           32  Pressure regulating valve 
           40  Controller 
         R 1  Compression chamber 
         R 2  Coil chamber