Patent Publication Number: US-2023139764-A1

Title: Power generation system

Description:
TECHNICAL FIELD 
     The present invention relates to a power generation system. 
     BACKGROUND ART 
     Conventionally, a power generation system including a wave power generator has been proposed as in Patent Literature 1. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: JP 2016-039130 A 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, it is necessary to install a member for a power generator or the like not to flow, such as an anchor. 
     Therefore, an object of the present invention is to provide a power generation system including a wave power generator that can be configured in a simple manner. 
     Solution to Problem 
     A power generation system according to the present invention includes: a power generation unit including a wave power generator; a power storage unit accumulating electric power obtained by the power generation unit; a production unit producing at least one of hydrogen and an organic hydride based on the electric power obtained by the power generation unit; and a tank located below compared to the wave power generator and storing at least one of the hydrogen and the organic hydride obtained by the production unit. 
     A power generation system according to the present invention includes: a power generation unit including a wave power generator; a power storage unit accumulating electric power obtained by the power generation unit; a production unit producing at least one of hydrogen and an organic hydride based on the electric power obtained by the power generation unit; and a tank located below compared to the production unit and under water, and storing at least one of the hydrogen and the organic hydride obtained by the production unit. 
     Some of the electric power obtained by the power generation unit such as the wave power generator is accumulated in the power storage unit, and the other of the electric power is used for hydrogenation or the like and accumulated as hydrogen or an organic hydride in the tank. 
     The tank can be used as a sinker of the power generation system. 
     By using the tank located under the water, it is possible to configure the power generation system including the wave power generator in a simple manner. 
     Preferably, the production unit is a hydrogenation unit producing the organic hydride from an aromatic compound. 
     The tank includes a first tank storing the aromatic compound and a second tank storing the organic hydride. 
     Some of the electric power obtained by the power generation unit such as the wave power generator is accumulated in the power storage unit, and the other of the electric power is used for hydrogenation and accumulated as an organic hydride containing hydrogen in the tank (the second tank). 
     The organic hydride accumulated in the second tank can be easily transported by a ship or the like as compared with a mode in which hydrogen is transported in a gaseous or liquid state, and hydrogen can be easily extracted and used at a place spaced away from a power generation system  1 . 
     The aromatic compound accumulated in the first tank and the organic hydride accumulated in the second tank can be used as a sinker of the power generation system. 
     By using the tank located under the water, it is possible to configure the power generation system  1  including the wave power generator in a simple manner. 
     More preferably, the wave power generator includes a float, a first movement member moving in a vertical direction in conjunction with a vertical movement of the float, a second movement member engaged with the first movement member to rotate based on a vertical movement of the first movement member, and a power generation device generating power based on a rotational force of the second movement member. 
     The power generation device can be disposed at a position where the waterproof treatment is easily performed, for example, on a base part. 
     More preferably, the power generation unit includes a wind power generator. 
     A rotational force of an impeller of the wind power generator and the rotational force of the second movement member are transmitted to the power generation device via a power transmission unit. 
     The power generation device can be shared by the wave power generator and the wind power generator. 
     Preferably, the power generation system further includes a base part located above compared to a float of the wave power generator and holding the power storage unit. 
     At least a part of the wave power generator passes through a tubular member or a bar-shaped member connecting the base part and the tank, and is held in a swingable state in the vertical direction. 
     The wave power generator can be held by utilizing the tubular member connecting the base part and the tank to each other. 
     More preferably, the tank has a donut shape. 
     The tubular member or the bar-shaped member extends from an outer wall on an inward side of the donut-shaped tank. 
     The aromatic compound passes through the inside of at least one of the tubular members. 
     The organic hydride passes through the inside of at least one of the tubular members other than the tubular member through which the aromatic compound passes inside. 
     Since the tank is formed in the donut side shape, it is less likely to break due to pressure from the outside, and it is less likely to fall down even though the base part or the like is disposed thereon. 
     A worker can enter the gap to perform maintenance work on the tank, or a mobile monitoring device can circulate along the gap between the tank and the cover to specify a damaged portion of the tank. 
     Preferably, the tank includes a first partition wall movable inside the tank. 
     The first partition wall is used to partition the first tank and the second tank. 
     By using the first partition wall, it is possible to adjust a size of the first tank that accumulates the aromatic compound and a size of the second tank that accumulates the organic hydride. 
     More preferably, the tank includes a third tank storing water or air. 
     The third tank is used to adjust a weight of the tank. 
     By adjusting the filling degree of water in the third tank, it becomes easy to adjust a sinking degree of the tank as a sinker according to the filling degree of the aromatic compound in the first tank  53   a  and the organic hydride in the second tank. 
     By filling the third tank with air, the tank can be easily floated. 
     More preferably, the tank includes a second partition wall movable inside the tank. 
     The second partition wall is used to partition the second tank and the third tank. 
     By using the second partition wall, it is possible to adjust a size of the second tank and a size of the third tank. 
     Preferably, the tank includes a third partition wall movable inside the tank. 
     The third partition wall is used to partition the third tank and the first tank. 
     More preferably, the hydrogenation unit produces the organic hydride from the aromatic compound using an organic hydride electrolytic synthesis method. 
     Preferably, the power generation system further includes a propulsion device provided below the wave power generator and driven based on the electric power from the power storage unit. 
     The power generation unit includes a wind power generator and a solar power generator. 
     The wind power generator and the solar power generator are provided on the base part. 
     A power generation system according to the present invention includes: a power generation unit including a wave power generator; a power storage unit accumulating electric power obtained by the power generation unit; a production unit producing at least one of hydrogen and an organic hydride based on the electric power obtained by the power generation unit; and a tank located below compared to the production unit and under water, and storing at least one of the hydrogen and the organic hydride obtained by the production unit. 
     Advantageous Effects of Invention 
     As described above, according to the present invention, it is possible to provide a power generation system including a wave power generator that can be configured in a simple manner. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a schematic view illustrating a configuration of a power generation system according to a first embodiment. 
         FIG.  2    is a schematic view illustrating a configuration of the power generation system in a height direction. 
         FIG.  3    is a perspective view of the power generation system. 
         FIG.  4    is a cross-sectional view illustrating a configuration of a tank in a state where a size of a first tank becomes large. 
         FIG.  5    is a cross-sectional view illustrating a configuration of a tank in a state where a size of a second tank and a size of a third tank become large. 
         FIG.  6    is a schematic view illustrating a configuration of a power generation system in a height direction according to a second embodiment. 
         FIG.  7    is a schematic view illustrating an internal structure of a wave power generator according to the second embodiment. 
         FIG.  8    is a view illustrating a configuration including an impeller, a power transmission unit, a female screw part, and a power generation device according to the second embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, present embodiments will be described with reference to the drawings. 
     Note that the embodiments are not limited to the following embodiments. In addition, contents described in one embodiment are similarly applied to another embodiment in principle. Further, the embodiments and modifications thereof can be appropriately combined. 
     Power Generation System  1   
     A power generation system  1  according to a first embodiment includes a power generation unit  10 , a base part  20 , a control unit  30 , a power storage unit  40 , a hydrogen storage unit  50 , and a propulsion device  60  (see  FIGS.  1  to  5   ). 
     The power generation system  1  is set such that the base part  20  is located above the water, a wave power generator  11  is located on a water surface, and a tank  53  is located under the water. 
     Power Generation Unit  10   
     The power generation unit  10  includes a wave power generator  11 , a solar power generator  13 , and a wind power generator  15 . 
     Wave Power Generator  11   
     The wave power generator  11  includes a float that swings according to the vertical movement of the wave, and generates electric power based on the vertical movement of said float. 
     The wave power generator  11  passes through a tubular member of the hydrogen storage unit  50 , and is held by said tubular member in a swingable state in a vertical direction. 
     However, the wave power generator  11  may pass through a bar-shaped member (e.g., a strut) which is other than the tube and which connects the base part  20  and the tank  53  to each other, and may be held by said bar-shaped member in a swingable state in the vertical direction. 
     In the first embodiment, an example in which the wave power generator  11  is held on the tubular member below the base part  20  will be described. 
     However, as in a second embodiment to be described later, some (e.g. a female screw part  11   c  and a power generation device  11   d ) of the wave power generator  11  may be disposed on the base part  20 . 
     Solar Power Generator  13   
     The solar power generator  13  generates electric power based on light such as sunlight. 
     The solar power generator  13  is provided on the base part  20 . 
     Wind Power Generator  15   
     The wind power generator  15  generates electric power based on a rotational force of an impeller that rotates by wind. 
     The wind power generator  15  is provided on the base part  20 . 
     AC power generated by the wave power generator  11  and AC power generated by the wind power generator  15  are supplied to the power storage unit  40  or a production unit  51  after being converted into DC power by an AC/DC converter. 
     Base Part  20   
     The base part  20  is located on the water, and holds the solar power generator  13 , the wind power generator  15 , the control unit  30 , the power storage unit  40 , the production unit  51 , and a first pump  58   a  to a sixth pump  58   f.    
     Control Unit  30   
     The control unit  30  controls each unit of the power generation system  1 . 
     For example, the control unit controls the driving of the production unit  51  or the like based on a state of charge of the power storage unit  40 . 
     Specifically, the control unit  30  controls each unit of the power generation system  1  so that, when the power storage unit  40  is not sufficiently charged, the electric power obtained by the power generation unit  10  is accumulated in the power storage unit  40 , rather than driving the production unit  51 . 
     When the power storage unit  40  is sufficiently charged, that is, when the power storage unit is fully charged, the production unit  51  or the like is driven by the electric power obtained by the power generation unit  10 , rather than charging the power storage unit  40 . 
     Power Storage Unit  40   
     The power storage unit  40  accumulates the electric power obtained by the power generation unit  10  to supply the electric power to electric equipment of the power generation system  1  such as the production unit  51 . 
     Hydrogen Storage Unit  50   
     The hydrogen storage unit  50  includes the production unit  51 , a tank  53 , a partition wall, a tubular member, and a pump. 
     The tank  53  of the hydrogen storage unit  50  includes a first tank  53   a,  a second tank  53   b,  and a third tank  53   c . The partition wall of the hydrogen storage unit  50  includes a first partition wall  55   a,  a second partition wall  55   b , and a third partition wall  55   c.    
     The tubular member of the hydrogen storage unit  50  includes a first pipe  57   a,  a second pipe  57   b,  a third pipe  57   c,  a fourth pipe  57   d,  a fifth pipe  57   e,  and a sixth pipe  57   f.    
     The pump of the hydrogen storage unit  50  includes a first pump  58   a,  a second pump  58   b,  a third pump  58   c,  a fourth pump  58   d,  a fifth pump  58   e,  and a sixth pump  58   f.    
     Production Unit  51   
     The production unit  51  is a first hydrogenation device that produces an organic hydride such as methylcyclohexane from an aromatic compound such as toluene using an organic hydride electrolytic synthesis method. 
     However, the production unit  51  may include a hydrogen production device that performs electrolysis of water to generate hydrogen, and a second hydrogenation device that adds the generated hydrogen to an aromatic compound to generate an organic hydride. 
     Tank  53   
     The tank  53  has a rotating body with its axis of rotation situated on an outer portion of a circle, i.e., a substantially donut shape. 
     The tank  53  is used to store the organic hydride and the like therein. 
     The tank  53  is also used as a sinker of the power generation system  1 . 
     The tank  53  is located under the water, and is connected to the base part  20  located on the water via the tubular member and the bar-shaped member. 
     In the tank  53 , three spaces (the first tank  53   a,  the second tank  53   b,  and the third tank  53   c ) are formed by the first partition wall  55   a,  the second partition wall  55   b , and the third partition wall  55   c.    
     The first tank  53   a  is used to store an aromatic compound in a space formed between the first partition wall  55   a  and the third partition wall  55   c.    
     The first tank  53   a  communicates with the first pipe  57   a  and the second pipe  57   b.    
     The second tank  53   b  is used to store an organic hydride in a space formed between the first partition wall  55   a  and the second partition wall  55   b.    
     The second tank  53   b  communicates with the third pipe  57   c  and the fourth pipe  57   d.    
     The third tank  53   c  is used to store water or air in a space formed between the second partition wall  55   b  and the third partition wall  55   c.    
     The third tank  53   c  communicates with the fifth pipe  57   e  and the sixth pipe  57   f.    
     Partition Wall 
     The first partition wall  55   a  is movable inside the tank  53 , and is used to partition the first tank  53   a  and the second tank  53   b.    
     A seal member (a first seal member  55   a   1 ) such as an O-ring is provided to maintain a sealing state between the first partition wall  55   a  and an inner wall of the tank  53 . 
     The first partition wall  55   a  may move by virtue of a pressure difference between the first tank  53   a  and the second tank  53   b,  or may move electrically via an actuator. 
     The second partition wall  55   b  is movable inside the tank  53 , and is used to partition the second tank  53   b  and the third tank  53   c.    
     A seal member (a second seal member  55   b   1 ) such as an O-ring is provided to maintain a sealing state between the second partition wall  55   b  and the inner wall of the tank  53 . 
     The second partition wall  55   b  may move by virtue of a pressure difference between the second tank  53   b  and the third tank  53   c,  or may move electrically via an actuator. 
     The third partition wall  55   c  is fixed inside the tank  53 , and is used to partition the third tank  53   c  and the first tank  53   a.    
     The third partition wall  55   c  may also be configured to be movable inside the tank  53 . 
     In this case, one of the first partition wall  55   a  and the second partition wall  55   b  may be fixed inside the tank  53 . 
     As the first partition wall  55   a  moves inside the tank  53 , the sizes of the first tank  53   a  and the second tank  53   b  change. 
     As the second partition wall  55   b  moves inside the tank  53 , the sizes of the second tank  53   b  and the third tank  53   c  change. 
     Tubular Member 
     The first pipe  57   a  has a lower end communicating with an inlet of the first tank  53   a  and an upper end communicating with a first external device (not illustrated) that supplies an aromatic compound to the first tank  53   a.    
     The second pipe  57   b  has a lower end communicating with an outlet of the first tank  53   a  and an upper end communicating with an inlet of the production unit  51 . 
     The third pipe  57   c  has a lower end communicating with an inlet of the second tank  53   b  and an upper end communicating with an outlet of the production unit  51 . 
     The fourth pipe  57   d  has a lower end communicating with an outlet of the second tank  53   b  and an upper end communicating with a second external device (not illustrated) that receives an organic hydride from the second tank  53   b.    
     The fifth pipe  57   e  has a lower end communicating with an inlet of the third tank  53   c  and an upper end being opened. 
     The sixth pipe  57   f  has a lower end communicating with an outlet of the third tank  53   c  and an upper end being opened. 
     The first and second external devices are installed in a ship, a land facility, or the like. 
     Pump 
     The first pump  58   a  is used to supply the aromatic compound from the first external device to the first tank  53   a.    
     The second pump  58   b  is used to supply the aromatic compound from the first tank  53   a  to the production unit  51 . 
     The third pump  58   c  is used to supply the organic hydride from the production unit  51  to the second tank  53   b.    
     The fourth pump  58   d  is used to supply the organic hydride from the second tank  53   b  to the second external device. 
     The fifth pump  58   e  is used to supply water or air from the outside to the third tank  53   c.    
     The sixth pump  58   f  is used to discharge the water or air from the third tank  53   c  to the outside. 
     Propulsion Device  60   
     The propulsion device  60  is constituted by a screw or the like, and is provided in an area located below compared to the wave power generator  11  and under the water (under the sea), for example, under the tank  53 . 
     The propulsion device  60  is driven on the basis of the electric power supplied from the power storage unit  40 , and is used to move the power generation system  1  and maintain the power generation system  1  at a predetermined position. 
     Operation 
     Next, an operation of the pumps of the power generation system  1  will be described. 
     At the time of starting an operation, the control unit  30  operates the first pump  58   a  to supply an aromatic compound from the first external device to the first tank  53   a.  Accordingly, the first tank  53   a  becomes in a large-size state (see  FIG.  4   ). 
     The second tank  53   b  is in a small-size state because an organic hydride has not been produced yet. 
     The control unit  30  operates the fifth pump  58   e  to supply water from the outside to the third tank  53   c.    
     Due to the weight of the aromatic compound in the first tank  53   a  and the weight of the water in the third tank  53   c , the tank  53  becomes in a sunk state under the water. 
     Electric power is generated by the wave power generator  11 , the solar power generator  13 , and the wind power generator  15  of the power generation unit  10 , and the generated electric power is accumulated in the power storage unit  40 . 
     When the power storage unit  40  is fully charged, the control unit  30  stops supplying electric power from the power generation unit  10  to the power storage unit  40 , and starts supplying electric power from the power generation unit  10  to the production unit  51 . 
     Here, the full charge is not limited to a 100% charged state, and may refer to a predetermined charged state in the range of about 80 to 90%. 
     In addition, the control unit  30  operates the second pump  58   b  to supply the aromatic compound from the first tank  53   a  to the production unit  51 . 
     The production unit  51  produces an organic hydride from the aromatic compound. 
     The control unit  30  operates the third pump  58   c  to supply the organic hydride produced by production unit  51  to the second tank  53   b.    
     Then, the amount of the organic hydride in the second tank  53   b  increases while the amount of the aromatic compound in the first tank  53   a  decreases. Accordingly, the first partition wall  55   a  moves so that the size of the second tank  53   b  increases while the size of the first tank  53   a  decreases (see  FIG.  5   ). 
     The control unit  30  adjusts an amount of the water in the third tank  53   c  in order to adjust a sinking degree of the tank  53 , for example, in order to maintain a constant waterline. 
     When the sinking degree of the tank  53  is shallow, the control unit  30  operates the fifth pump  58   e  to supply water from the outside to the third tank  53   c.    
     In this case, the second partition wall  55   b  moves so that the size of the third tank  53   c  increases. 
     When the sinking degree of the tank  53  is deep, the control unit  30  operates the sixth pump  58   f  to discharge the water in the third tank  53   c  to the outside. 
     In this case, the second partition wall  55   b  moves so that the size of the third tank  53   c  decreases (see  FIG.  4   ). 
     In order for the tank  53  to rise up on the water for the purpose of performing the maintenance of the tank  53  or the like, the control unit  30  operates the sixth pump  58   f  to discharge the water in the third tank  53   c  to the outside and operates the fifth pump  58   e  to supply air from the outside to the third tank  53   c.    
     In this case, due to the buoyancy of the tank  53 , the tank  53  rises up to be close to the water surface. 
     Effect of Accumulating Electric Power and Organic Hydride 
     In the first embodiment, some of the electric power obtained by the power generation unit  10  such as the wave power generator  11  is accumulated in the power storage unit  40 , and the other of the electric power is used for hydrogenation and accumulated as an organic hydride containing hydrogen in the tank  53  (the second tank  53   b ). 
     The electric power accumulated in power storage unit  40  is used to drive electric equipment of the power generation system  1  and drive external electric equipment. 
     In addition, the power storage unit  40  may be detached in a state where electric power is accumulated therein and used to drive external electric equipment. 
     The organic hydride accumulated in the second tank  53   b  can be easily transported by a ship or the like as compared with a mode in which hydrogen is transported in a gaseous or liquid state, and hydrogen can be easily extracted and used at a place spaced away from the power generation system  1 . 
     The aromatic compound accumulated in the first tank  53   a  and the organic hydride accumulated in the second tank  53   b  can be used as a sinker of the power generation system  1 . 
     By using the tank  53  located under the water, it is possible to configure the power generation system  1  including the wave power generator  11  in a simple manner. 
     Effect of Holding Wave Power Generator Using Pipe of Hydrogen Storage Unit  50   
     At least a part (a float or the like) of the wave power generator  11  passes through a pipe of the hydrogen storage unit  50  such as the first pipe  57   a  in a swingable state in the vertical direction, and is held by said pipe. 
     Therefore, the wave power generator  11  can be held by utilizing a tubular member or the like connecting the base part  20  and the tank  53  to each other. 
     Effect of Forming Tank in Doughnut Shape 
     Since the tank  53  is formed in a donut side shape, it is less likely to break due to pressure from the outside, and it is less likely to fall down even though the base part  20  or the like is disposed thereon. 
     Effect of Providing First Partition Wall 
     By using the first partition wall  55   a,  it is possible to adjust a size of the first tank  53   a  that accumulates the aromatic compound and a size of the second tank  53   b  that accumulates the organic hydride according to the degree of filling. 
     Effect of Providing Third Tank  53   c    
     By adjusting the filling degree of water in the third tank  53   c,  it becomes easy to adjust a sinking degree of the tank  53  as a sinker according to the filling degree of the aromatic compound in the first tank  53   a  and the organic hydride in the second tank  53   b.    
     By filling the third tank  53   c  with air, the tank  53  can be easily floated. 
     Effect of Providing Second Partition Wall 
     In addition, by using the second partition wall  55   b,  it is possible to adjust a size of the second tank  53   b  and a size of the third tank  53   c  that accumulates water or air. 
     Mode in which Hydrogen is Stored 
     Note that, as an example of the first embodiment, it has been described that some of electric power obtained by the power generation unit  10  is stored in the tank  53  as an organic hydride containing hydrogen. 
     However, the substance stored in the tank  53  is not limited to the organic hydride as long as the tank  53  is disposed below compared to at least one of the wave power generator  11  and the production unit  51  for use as a sinker under the water. For example, hydrogen obtained by electrolyzing water may be stored in a gaseous or liquid state in the tank  53 . 
     In this case, the production unit  51  functions as a hydrogen production device electrolyzing water to produce hydrogen. 
     Effect of Accumulating Electric Power and Hydrogen 
     In the first embodiment, some of the electric power obtained by the power generation unit  10  such as the wave power generator  11  is accumulated in the power storage unit  40 , and the other of the electric power is used to produce hydrogen and the hydrogen is accumulated in the tank  53 . 
     The electric power accumulated in power storage unit  40  is used to drive electric equipment of the power generation system  1  and drive external electric equipment. 
     In addition, the power storage unit  40  may be detached in a state where electric power is accumulated therein and used to drive external electric equipment. 
     Also, the tank  53  can be used as a sinker of the power generation system  1 . 
     By using the tank  53  located under the water, it is possible to configure the power generation system  1  including the wave power generator  11  in a simple manner. 
     Specific Example of Wave Power Generator  11   
     As an example of the first embodiment, it has been described that the float and the power generation device of the wave power generator  11  are housed in one case and are located below compared to the base part  20 . 
     Specifically, a mode is conceivable that the vertical movement of the float may cause a change of an air chamber in volume, and electric power may be generated by a rotation of a turbine based on said change of the air chamber in volume. 
     Alternatively, a mode is conceivable that the vertical movement of the float may cause a rotation of a pinion of the power generation device engaged with a rack of the tubular member, and electric power may be generated based on said rotation of the pinion. 
     Alternatively, a mode is conceivable that the vertical movement of the float may cause a rotation of a screw about an axis parallel to the vertical direction in which the tubular member extends, while the screw moves in the vertical direction to be located on the water above the float or located under the water below the float, and electric power may be generated based on said rotation of the screw. 
     Note that said screw is not limited to rotating about the axis parallel to the vertical direction, and may rotate about an axis parallel to a horizontal direction. In this case, said screw rotates according to the flow of the tide in the transverse direction. Like the propulsion device  60 , said screw may also be located under the tank  53 . 
     However, the wave power generator  11  is not limited to these modes, and may have another configuration (a second embodiment, see  FIGS.  6  to  8   ). 
     The wave power generator  11  according to the second embodiment includes a float  11   a,  a male screw part (a first movement member)  11   b,  the female screw part (a second movement member)  11   c,  and the power generation device  11   d . The male screw part  11   b  is provided on an outer wall of the tubular member (e.g., the first pipe  57   a ) to cover a side surface of said tubular member. 
     The male screw part  11   b  is fixed to an upper side of the float  11   a  to move in the vertical direction as the float  11   a  moves in the vertical direction. 
     The female screw part  11   c  is engaged with the male screw part  11   b  in a state where its movement in the vertical direction is restrained. 
     Accordingly, as the male screw part  11   b  moves in the vertical direction, the female screw part  11   c  rotates, rather than moving in the vertical direction. 
     The female screw part  11   c  and the power generation device  11   d  are disposed, for example, on the base part  20 . A part of the male screw part  11   b  and the float  11   a  are disposed below the base part  20 . 
     In accordance with the vertical movement of the male screw part  11   b,  the female screw part  11   c  rotates, and the power generation device  11   d  generates power based on a rotational force of the female screw part  11   c.    
     In this case, the power generation device  11   d  can be disposed at a position where the waterproof treatment is easily performed, for example, on the base part  20 . 
     Note that the female screw part  11   c  and the power generation device  11   d  may be included in a case including the float  11   a  to move in the vertical direction together with the float  11   a.  In this case, the male screw part  11   b  is fixed to the tubular member without being operated in conjunction with the vertical movement of the float  11   a.    
     Cover  59  of Tank  53   
     As illustrated in  FIG.  6   , the tank  53  may be provided with a cover  59  that entirely covers the tank  53 . 
     By providing the cover  59 , the tank  53  can be prevented from being corroded by seawater or the like. 
     For example, the cover  59  is made of pressure-resistance reinforced transparent hard glass. 
     In this case, it becomes easy to visually recognize a damaged state of the tank  53  or the like from the outside of the cover  59 . 
     In addition, it is preferable that there is a gap between an inner wall of the cover  59  and an outer wall of the tank  53 . 
     A worker can enter the gap to perform maintenance work on the tank  53 , or a mobile monitoring device can circulate along the gap between the tank  53  and the cover  59  to specify a damaged portion of the tank  53 . 
     Sharing of Power Generation Device 
     As an example of the first embodiment, it has been described that the wave power generator  11  and the wind power generator  15  are separately configured. 
     However, the power generation device  11   d  generating power based on the rotational force of the female screw part  11   c  or the like of the wave power generator  11  may also generate power based on a rotational force of an impeller  15   a  of the wind power generator  15 . 
     In this case, a power transmission unit  11   e  is provided between a member that performs a rotational motion of the wave power generator  11 , such as the female screw part  11   c , and a member that performs a rotational motion of the wind power generator  15 , such as the impeller  15   a.    
     The rotational force of the female screw part  11   c  and the rotational force of the impeller  15   a  are transmitted to the power generation device  11   d  via the power transmission unit  11   e,  and the power generation device  11   d  generates power based on these rotational forces. 
     In this way, the power generation device can be shared by the wave power generator  11  and the wind power generator  15 . 
     Although some embodiments of the present invention have been described, these embodiments have been presented as examples, and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. The invention set forth in the claims and equivalents thereof are intended to cover those embodiments and modifications thereof as falling within the scope and gist of the invention. 
     REFERENCE SIGNS LIST 
       1  Power generation system 
       10  Power generation unit 
       11  Wave power generator 
       11   a  Float 
       11   b  Male screw part 
       11   c  Female screw part 
       11   d  Power generation device 
       11   e  Power transmission unit 
       13  Solar power generator 
       15  Wind power generator 
       15   a  Impeller 
       20  Base part 
       30  Control unit 
       40  Power storage unit 
       50  Hydrogen storage unit 
       51  Production unit (hydrogenation device or hydrogen production device) 
       53  Tank 
       53   a  First tank 
       53   b  Second tank 
       53   c  Third tank 
       55   a  First partition wall 
       55   a   1  First seal member 
       55   b  Second partition wall 
       55   b   1  Second seal member 
       55   c  Third partition wall 
       57   a  First pipe 
       57   b  Second pipe 
       57   c  Third pipe 
       57   d  Fourth pipe 
       57   e  Fifth pipe 
       57   f  Sixth pipe 
       58   a  First pump 
       58   b  Second pump 
       58   c  Third pump 
       58   d  Fourth pump 
       58   e  Fifth pump 
       58   f  Sixth pump 
       59  Cover 
       60  Propulsion device