Power generation system

Abstract

To provide a power generation system capable of properly recovering expansion energy when a hydrogen gas and an oxygen gas generated by electrolysis of fresh water by an electrolysis device on the sea bottom rises to a sea level.SOLUTION: A power generation system includes: a hydrogen line 8 for connecting an electrolysis device 5 on the sea bottom and a hydrogen expansion turbine 6 above the sea level 2; a hydrogen switch valve 9 disposed on an upper part with respect to the sea level 2 of the hydrogen line 8, discharges a gas-liquid two-phase flow of the hydrogen gas and fresh water 4 to the sea level 2 when it exists in the hydrogen line 8 of the part and guides the hydrogen gas to the hydrogen expansion turbine 6 when only the hydrogen gas exists; an oxygen line 10 for connecting the electrolysis device 5 and an oxygen expansion turbine 7 above the seal level 2; and an oxygen switch valve 11 disposed on a part above the seal level 2 of the oxygen line 10 to discharge the gas-liquid two-phase flow of the oxygen gas and the fresh water 4 to the seal level 2 when it exists in the oxygen line 10 of the part and to guide the oxygen gas to the oxygen expansion turbine 7 when only the oxygen gas exists.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a power generation system that generates power by utilizing hydrogen gas and oxygen gas generated by electrolysis of water. [Background technology]

[0002] Conventionally, a power generation system has been known that generates electricity using hydrogen gas and oxygen gas generated by electrolyzing water, in which seawater is electrolyzed underwater, a two-phase gas-liquid flow consisting of seawater and hydrogen gas generated by electrolysis is allowed to expand while rising to the sea surface, hydrogen gas and oxygen gas are extracted from the two-phase gas-liquid flow at the sea surface, the extracted mixed gas of hydrogen gas and oxygen gas is combusted by combustion power generation means to generate electricity, and a water current power generation means is driven by the flow of the fluid (seawater) after the hydrogen gas and oxygen gas have been extracted from the two-phase gas-liquid flow to generate electricity (see Patent Document 1).

[0003] According to this power generation system, in addition to being able to generate electricity by a combustion power generation means that utilizes the combustion energy produced when hydrogen gas and oxygen gas are combusted, it is also possible to generate electricity by a water current power generation means that utilizes the flow of the above-mentioned fluid (seawater) generated by the buoyancy of hydrogen gas bubbles and oxygen gas bubbles as they expand and rise from the sea surface. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5226895 [Patent Document 2] Japanese Patent Application Publication No. 55-119888 Summary of the Invention [Problem to be solved by the invention]

[0005] The power generation system described in Patent Document 1 generates power by burning expanded hydrogen gas and oxygen gas extracted from a gas-liquid two-phase flow of hydrogen gas, oxygen gas, and seawater at the sea surface using a combustion power generation means. Therefore, it cannot be said that the expansion energy of the gas itself, which is generated when the hydrogen gas and oxygen gas generated in the electrolysis device underwater rises to the sea surface, is effectively recovered.

[0006] In addition, in Reference 1, hydrogen gas and oxygen gas are extracted from a two-phase gas-liquid flow of hydrogen gas, oxygen gas, and seawater, and the mixed gas is combusted. This means that a gas mixture of hydrogen gas and oxygen gas is handled, which is not preferable from a safety standpoint considering the possibility of an explosion triggered by a spark or the like when a switch is turned on and off.

[0007] Furthermore, although Document 1 describes the use of hydrogen gas and oxygen gas generated by electrolyzing seawater in the ocean, when seawater is electrolyzed in the first place, hydrogen gas and chlorine gas are generated, but oxygen gas is not generated (see Patent Document 2, page 1, lines 1-2 in the lower right column). Therefore, the premise that hydrogen gas and oxygen gas are combusted by a combustion power generation means does not hold up.

[0008] The object of the present invention, which was devised in consideration of the above circumstances, is to provide a highly safe power generation system that can generate electricity by appropriately recovering the expansion energy of hydrogen gas and oxygen gas generated by electrolyzing fresh water in an electrolysis device on the seabed or underwater as the gas rises to the sea surface. [Means for solving the problem]

[0009] According to the present invention, which has been devised to achieve the above object, there is provided a power generation system comprising: a water supply line that supplies fresh water from above the sea surface to the seabed or underwater at a predetermined depth; an electrolysis device that is connected to the water supply line and is placed on the seabed or underwater and electrolyzes the fresh water supplied from the water supply line to produce hydrogen gas and oxygen gas; a hydrogen expansion turbine that is rotated and driven by the hydrogen gas produced in the electrolysis device and is placed above the sea surface; and an oxygen expansion turbine that is rotated and driven by the oxygen gas produced in the electrolysis device and is placed above the sea surface. The hydrogen line that connects the electrolysis device and the hydrogen expansion turbine is placed from the seabed or underwater to above the sea surface. the hydrogen line, when a two-phase gas-liquid flow of hydrogen gas and fresh water is present in the hydrogen line, discharges the two-phase gas-liquid flow to the sea surface, and when only hydrogen gas is present in the hydrogen line, directs the hydrogen gas to the hydrogen expansion turbine; an oxygen line, connecting the electrolyzer and the oxygen expansion turbine, disposed from the seabed or subsea to above the sea surface; and an oxygen switching valve, provided in the oxygen line above the sea surface, for discharging the two-phase gas-liquid flow to the sea surface when a two-phase gas-liquid flow of oxygen gas and fresh water is present in the oxygen line, and directing the oxygen gas to the oxygen expansion turbine when only oxygen gas is present in the oxygen line.

[0010] In the power generation system of the present invention, a hydrogen two-phase flow sensor is provided in a portion of the hydrogen line above sea level, which detects whether a gas-liquid two-phase flow of hydrogen gas and fresh water or only hydrogen gas is present in the hydrogen line, and an oxygen two-phase flow sensor is provided in a portion of the oxygen line above sea level, which detects whether a gas-liquid two-phase flow of oxygen gas and fresh water or only oxygen gas is present in the oxygen line, and a control unit is provided which is connected to the hydrogen two-phase flow sensor and the oxygen two-phase flow sensor, respectively, and controls the hydrogen switch valve and the oxygen switch valve, respectively, and the control unit switches the hydrogen switch valve to the side discharging to the sea surface when the hydrogen two-phase flow sensor detects a gas-liquid two-phase flow of hydrogen gas and fresh water, switches the hydrogen switch valve to the hydrogen expansion turbine side when the hydrogen two-phase flow sensor detects only hydrogen gas, switches the oxygen switch valve to the side discharging to the sea surface when the oxygen two-phase flow sensor detects a gas-liquid two-phase flow of oxygen gas and fresh water, and switches the oxygen switch valve to the oxygen expansion turbine side when the oxygen two-phase flow sensor detects only oxygen gas.

[0011] The power generation system according to the present invention may include a combustor that combusts the hydrogen gas discharged from the hydrogen expansion turbine and the oxygen gas discharged from the oxygen expansion turbine, and a gas turbine that is rotationally driven by the combustion gas generated in the combustor.

[0012] In the power generation system according to the present invention, the water supply line may be provided with a water flow rate control valve for controlling the amount of fresh water supplied to the electrolyzer.

[0013] In the power generation system according to the present invention, the flow path cross-sectional area of ​​the hydrogen line may be twice as large as the flow path cross-sectional area of ​​the oxygen line. Effect of the Invention

[0014] The power generation system according to the present invention exhibits the following functions and effects. (1) Fresh water is supplied from above the sea surface through a water supply line to the seabed or underwater at a specified depth, and when electrolysis of the fresh water begins in an electrolysis device on the seabed or underwater, hydrogen gas and oxygen gas are produced. (2) The hydrogen gas generated in the electrolyzer rises through the hydrogen line from the electrolyzer. As the water depth becomes shallower, the hydrogen gas expands and rises in response to the decreasing pressure. The fresh water in the electrolyzer is caught in the rising hydrogen gas, and a two-phase flow of hydrogen gas and fresh water rises in the hydrogen line. The fresh water in the two-phase flow of hydrogen gas and fresh water rising in the hydrogen line is subjected to a downward force due to gravity acting on the fresh water. Therefore, immediately after the start of electrolysis, a two-phase flow of hydrogen gas and fresh water exists in the part of the hydrogen line above the sea level, but after a certain time has passed since the start of electrolysis, only hydrogen gas exists in the part of the hydrogen line above the sea level. The hydrogen switching valve installed in the part of the hydrogen line above the sea level discharges the two-phase flow of hydrogen gas and fresh water to the sea surface when a two-phase flow of hydrogen gas and fresh water exists in the hydrogen line, and guides the hydrogen gas to the hydrogen expansion turbine when only hydrogen gas exists in the hydrogen line. As a result, only hydrogen gas is introduced to the hydrogen expansion turbine, and a two-phase gas-liquid flow of hydrogen gas and fresh water is not introduced to the hydrogen expansion turbine, which prevents damage to the hydrogen expansion turbine caused by a two-phase gas-liquid flow being introduced to the hydrogen expansion turbine, and allows the expansion energy of the hydrogen gas to be appropriately recovered as it rises from the seabed or underwater to the sea surface. (3) Similarly, oxygen gas generated in the electrolyzer rises from the electrolyzer through the oxygen line, expanding as the water depth decreases, and the fresh water in the electrolyzer is caught in the rising oxygen gas, causing a two-phase flow of oxygen gas and fresh water to rise in the oxygen line. The fresh water in the two-phase flow of oxygen gas and fresh water rising in the oxygen line is subjected to a downward force due to gravity acting on the fresh water. Therefore, immediately after the start of electrolysis, a two-phase flow of oxygen gas and fresh water exists in the part of the oxygen line above the sea level, but after a certain time has passed since the start of electrolysis, only oxygen gas exists in the part of the oxygen line above the sea level. The oxygen switching valve installed in the part of the oxygen line above the sea level discharges the two-phase flow of oxygen gas and fresh water to the sea surface when a two-phase flow of oxygen gas and fresh water exists in the oxygen line, and directs the oxygen gas to the oxygen expansion turbine when only oxygen gas exists in the oxygen line. As a result, only oxygen gas is introduced to the oxygen expansion turbine, and a two-phase flow of oxygen gas and fresh water is not introduced, which prevents damage to the oxygen expansion turbine caused by a two-phase flow being introduced to the oxygen expansion turbine, and allows the expansion energy of the gas when the oxygen gas rises from the seabed or underwater to the sea surface to be appropriately recovered. (4) In addition, the hydrogen gas generated in the electrolysis device located on the seabed or underwater passes through a hydrogen line to drive a hydrogen expansion turbine above the sea level, and the oxygen gas generated in the electrolysis device passes through an oxygen line to drive an oxygen expansion turbine above the sea level. This means that hydrogen gas and oxygen gas do not mix in the hydrogen expansion turbine and the oxygen expansion turbine, resulting in a high level of safety. (5) In summary, the power generation system of the present invention can appropriately recover the expansion energy of hydrogen gas and oxygen gas generated by electrolyzing fresh water in an electrolysis device on the seabed or underwater as the gas rises to the sea surface, and is highly safe. [Brief description of the drawings]

[0015] [Figure 1]FIG. 1 is an explanatory diagram showing an overview of a power generation system according to an embodiment of the present invention, and is an explanatory diagram showing a first step (power generation preparation 1) of operation. [Diagram 2] FIG. 2 is an explanatory diagram showing a second step (power generation preparation 2) following FIG. [Diagram 3] FIG. 3 is an explanatory diagram showing a third step (power generation preparation 3) following FIG. [Figure 4] FIG. 4 is an explanatory diagram showing a fourth step (power generation preparation 4) following FIG. [Diagram 5] FIG. 5 is an explanatory diagram showing a fifth step (power generation state) following FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values ​​shown in the embodiment are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In this specification and drawings, elements having substantially the same functions and configurations are given the same reference numerals to avoid repeated explanations, and elements not directly related to the present invention are not shown.

[0017] (Outline of the power generation system) An overview of a power generation system 1 according to an embodiment of the present invention is shown in Figures 1 to 5. As shown in Figure 5, the power generation system 1 according to this embodiment includes a water supply line 3 that supplies fresh water from above the sea surface 2 to the seabed or submerged at a predetermined depth, an electrolysis device 5 that is connected to the water supply line 3 and placed on the seabed or submerged, and that electrolyzes the fresh water 4 supplied from the water supply line 3 to generate hydrogen gas and oxygen gas, a hydrogen expansion turbine 6 that is rotationally driven by the hydrogen gas generated by the electrolysis device 5 and placed above the sea surface 2, and an oxygen expansion turbine 7 that is rotationally driven by the oxygen gas generated by the electrolysis device 5 and placed above the sea surface 2.

[0018] As shown in Fig. 5, this power generation system 1 includes a hydrogen line 8 that connects the electrolyzer 5 and the hydrogen expansion turbine 6 and is disposed from the seabed or subsea to above the sea level 2, and a hydrogen switch valve 9 that is provided on the hydrogen line 8 above the sea level 2. As shown in Figs. 3 and 4, the hydrogen switch valve 9 discharges a gas-liquid two-phase flow of hydrogen gas and fresh water (indicated by hatched X and hatched Y) to the sea level 2 when this gas-liquid two-phase flow is present in the hydrogen line 8 above the sea level 2, and guides the hydrogen gas to the hydrogen expansion turbine 6 when only hydrogen gas (indicated by open Z) is present in the hydrogen line 8 above the sea level 2 as shown in Fig. 5.

[0019] As shown in Fig. 5, the power generation system 1 includes an oxygen line 10 that connects the electrolyzer 5 and the oxygen expansion turbine 7 and is disposed from the seabed or underwater to above the sea level 2, and an oxygen switching valve 11 that is provided in a portion of the oxygen line 10 above the sea level 2. As shown in Figs. 3 and 4, when a gas-liquid two-phase flow of oxygen gas and fresh water (shown by hatching X and hatching Y) is present in the oxygen line 10 above the sea level 2, the oxygen switching valve 11 discharges the gas-liquid two-phase flow to the sea level 2, and when only oxygen gas (shown by hollow Z) is present in the oxygen line 10 above the sea level 2, as shown in Fig. 5, the oxygen switching valve 11 guides the oxygen gas to the oxygen expansion turbine 7. Each component will be described below.

[0020] (Water supply line 3) As shown in Fig. 5, a water supply line 3 supplies fresh water 4 to an electrolyzer 5 located on the seabed or in the sea at a predetermined depth (for example, several hundred meters to one thousand and several hundred meters, or several thousand meters) from above the sea surface 2. A water tank 12 is connected to a portion of the water supply line 3 above the sea surface 2, and fresh water 4 is supplied to the water tank 12 via a water supply pipe 13. The fresh water 4 supplied to the water tank 12 is an electrolyte that is electrolyzed in the electrolyzer 5, and an appropriate amount of sodium hydroxide, sulfuric acid, etc. is added to ensure conductivity.

[0021] (Electrolysis device 5) As shown in Fig. 5, an electrolyzer 5 for electrolyzing fresh water 4 supplied from a water supply line 3 is disposed on the seabed or in the sea at a predetermined depth. The electrolyzer 5 includes a water tank 5a for storing the fresh water 4 supplied from the water supply line 3, an anode 5b and a cathode 5c arranged horizontally at a distance in the water tank 5a, an oxygen catch tank 5d formed by upwardly expanding the water tank 5a above the anode 5b, a hydrogen catch tank 5e formed by upwardly expanding the water tank 5a above the cathode 5c, and a battery BAT disposed above the sea surface 2. The positive electrode of the battery BAT is connected to the anode 5b, and the negative electrode of the battery BAT is connected to the cathode 5c.

[0022] As shown in FIG. 5, when a voltage is applied from the battery BAT to the anode 5b and cathode 5c, the fresh water 4 in the water tank 5a is electrolyzed, generating oxygen gas from the anode 5b and hydrogen gas from the cathode 5c. The open circles in the figure represent oxygen gas bubbles and hydrogen gas bubbles. Here, due to the electrolysis reaction formula "2H2O→2H2+O2", twice as much hydrogen gas is generated as oxygen gas. The oxygen gas generated at the anode 5b is captured in the oxygen catch tank 5d, and the hydrogen gas generated at the cathode 5c is captured in the hydrogen catch tank 5e.

[0023] (Hydrogen expansion turbine 6, oxygen expansion turbine 7) As shown in FIG. 5, above sea level 2, a hydrogen expansion turbine 6 driven by hydrogen gas produced in the electrolyzer 5 is disposed, and an oxygen expansion turbine 7 driven by oxygen gas produced in the electrolyzer 5 is disposed. As described above, the volume of hydrogen gas produced in the electrolyzer 5 is twice the volume of oxygen gas, so the capacity of the hydrogen expansion turbine 6 is twice the capacity of the oxygen expansion turbine 7. A first generator G1 driven by the hydrogen expansion turbine 6 is connected to the hydrogen expansion turbine 6, and a second generator G2 driven by the oxygen expansion turbine 7 is connected to the oxygen expansion turbine 7. Most of the electricity generated in the first generator G1 and the second generator G2 is transmitted to the power consumption area, and a portion is supplied to the battery BAT that serves as the power source for the electrolyzer 5.

[0024] (Hydrogen Line 8) As shown in Fig. 5, the hydrogen catch tank 5e of the electrolyzer 5 and the hydrogen expansion turbine 6 are connected by a hydrogen line 8. The hydrogen gas generated in the electrolyzer 5 and caught in the hydrogen catch tank 5e rises through the hydrogen line 8, and as the water depth becomes shallower, the hydrogen gas rises while expanding in response to the decreasing pressure. As the fresh water 4 in the electrolyzer 5 is entrained in the rising hydrogen gas, a two-phase gas-liquid flow of the hydrogen gas and the fresh water 4 rises in the hydrogen line 8. Here, the fresh water 4 in the two-phase gas-liquid flow of the hydrogen gas and the fresh water 4 rising in the hydrogen line 8 is subjected to a downward force due to gravity acting on the fresh water 4.

[0025] For this reason, as shown in Figs. 3 and 4, immediately after the start of electrolysis, a gas-liquid two-phase flow of hydrogen gas and fresh water 4 (shown by hatching X and hatching Y) is present in the portion of the hydrogen line 8 above the sea level 2, but as shown in Fig. 5, after a predetermined time has elapsed since the start of electrolysis, only hydrogen gas (shown by open Z) is present in the portion of the hydrogen line 8 above the sea level 2. In Figs. 3 to 5, the density of the hatching X and Y in the hydrogen line 8 indicates the proportion of the liquid (fresh water 4) in the gas-liquid two-phase flow of hydrogen gas and fresh water 4 ascending the hydrogen line 8. If the hatching is thick like X, the proportion of the liquid (fresh water 4) in the gas-liquid two-phase flow is high, if the hatching is thin like Y, the proportion of the liquid (fresh water 4) in the gas-liquid two-phase flow is low, and if there is no hatching and it is open Z, it indicates that only gas (hydrogen gas) is present.

[0026] That is, as shown in FIG. 3, immediately after the start of electrolysis, the gas-liquid two-phase flow of hydrogen gas and fresh water 4 rising in the hydrogen line 8 is generally dark hatched X, with a high proportion of liquid (fresh water 4). After a certain amount of time has passed, as shown in FIG. 4, the fresh water in the gas-liquid two-phase flow of hydrogen gas and fresh water 4 rising in the hydrogen line 8 descends due to gravity acting on the fresh water 4, so that the proportion of liquid (fresh water 4) remains dark hatched X in the hydrogen line 8 about halfway from the electrolyzer 5 to the sea level 2, but the proportion of liquid (fresh water 4) becomes light hatched Y in the hydrogen line 8 from about halfway to the sea level 2. After a certain amount of time has passed, the liquid (fresh water 4) in the gas-liquid two-phase flow continues to descend due to gravity, and as shown in FIG. 5, the hydrogen line 8 becomes dark hatched X, light hatched Y, and open Z from the bottom, with only hydrogen gas present in the part of the hydrogen line 8 above the sea level 2.

[0027] (Hydrogen switching valve 9) As shown in Fig. 5, a hydrogen switching valve 9 is provided in a portion of the hydrogen line 8 above sea level 2. The hydrogen switching valve 9 is a three-way valve, and as shown in Figs. 3 and 4, when a gas-liquid two-phase flow of hydrogen gas and fresh water 4 is present in the hydrogen line 8 above sea level 2, the hydrogen switching valve 9 discharges the gas-liquid two-phase flow from a discharge pipe 14 to sea level 2, and as shown in Fig. 5, when only hydrogen gas is present in the hydrogen line 8 above sea level 2, the hydrogen gas is guided to the hydrogen expansion turbine 6. Note that in the three-way valve constituting the hydrogen switching valve 9 shown in Figs. 3 to 5, the open portions represent the open valve state, and the black portions represent the closed valve state.

[0028] (Oxygen Line 10) As shown in Fig. 5, the oxygen catch tank 5d of the electrolyzer 5 and the oxygen expansion turbine 7 are connected by an oxygen line 10. The oxygen gas generated in the electrolyzer 5 and caught in the oxygen catch tank 5d rises through the oxygen line 10, and as the water depth becomes shallower, the oxygen gas rises while expanding in response to the decreasing pressure. As the fresh water 4 in the electrolyzer 5 is entrained in the rising oxygen gas, a two-phase gas-liquid flow of the oxygen gas and the fresh water 4 rises in the oxygen line 10. Here, the fresh water 4 in the two-phase gas-liquid flow of the oxygen gas and the fresh water 4 rising in the oxygen line 10 is subjected to a downward force due to gravity acting on the fresh water 4.

[0029] Therefore, as shown in Fig. 3 and Fig. 4, immediately after the start of electrolysis, a gas-liquid two-phase flow of oxygen gas and fresh water 4 (shown by hatching X and hatching Y) exists in the part of the oxygen line 10 above the sea level 2, but as shown in Fig. 5, after a certain time has elapsed since the start of electrolysis, only oxygen gas (shown by white) exists in the part of the oxygen line 10 above the sea level 2. In Fig. 3 to Fig. 5, the density of the hatching in the oxygen line 10 indicates the proportion of the liquid (fresh water 4) in the gas-liquid two-phase flow of oxygen gas and fresh water 4 ascending the oxygen line 10. If the hatching is thick like X, the proportion of the liquid (fresh water 4) in the gas-liquid two-phase flow is high, if the hatching is thin like Y, the proportion of the liquid (fresh water 4) in the gas-liquid two-phase flow is low, and if there is no hatching and it is white like Z, it indicates that only gas (oxygen gas) exists.

[0030] That is, as shown in Fig. 3, immediately after the start of electrolysis, the gas-liquid two-phase flow of oxygen gas and fresh water 4 rising in the oxygen line 10 is generally dark hatched X, with a high proportion of liquid (fresh water 4). After a certain amount of time has passed, as shown in Fig. 4, the fresh water 4 in the gas-liquid two-phase flow of oxygen gas and fresh water 4 rising in the oxygen line 10 descends due to gravity acting on the fresh water 4, so that the proportion of liquid (fresh water 4) remains dark hatched X in about the halfway point of the oxygen line 10 from the electrolyzer 5 to the sea level 2, but the proportion of liquid (fresh water 4) becomes light hatched Y in the oxygen line 10 from about the halfway point to the sea level 2. After a certain amount of time has passed, the liquid (fresh water 4) in the gas-liquid two-phase flow continues to descend due to gravity, and as shown in Fig. 5, the inside of the oxygen line 10 becomes dark hatched X, light hatched Y, and open Z from the bottom, with only oxygen gas being present in the part of the oxygen line 10 above the sea level 2.

[0031] (Oxygen switching valve 11) As shown in Fig. 5, an oxygen switching valve 11 is provided in a portion of the oxygen line 10 above the sea level 2. The oxygen switching valve 11 is a three-way valve, and when a gas-liquid two-phase flow of oxygen gas and fresh water is present in the oxygen line 10 above the sea level 2 as shown in Figs. 3 and 4, the gas-liquid two-phase flow is discharged from a discharge pipe 15 to the sea level 2, and when only oxygen gas is present in the oxygen line above the sea level 2 as shown in Fig. 5, the oxygen gas is guided to the oxygen expansion turbine 7. Note that in the three-way valve constituting the oxygen switching valve 11 shown in Figs. 3 to 5, the open parts represent the valve open state, and the black parts represent the valve closed state.

[0032] (Hydrogen two-phase flow sensor 16, Oxygen two-phase flow sensor 17) 5, a hydrogen two-phase flow sensor 16 is provided in a portion of the hydrogen line 8 above sea level 2, which detects whether a gas-liquid two-phase flow of hydrogen gas and fresh water or only hydrogen gas is present in that portion of the hydrogen line 8. Also, an oxygen two-phase flow sensor 17 is provided in a portion of the oxygen line 10 above sea level 2, which detects whether a gas-liquid two-phase flow of oxygen gas and fresh water or only oxygen gas is present in that portion of the oxygen line 10.

[0033] The hydrogen two-phase flow sensor 16 and the oxygen two-phase flow sensor 17 shown in Fig. 5 may be known two-phase flow sensors using, for example, the conductance method, the stylus method, ultrasonic waves, laser (light), or radiation such as x-rays or gamma rays. A two-phase flow sensor using the conductance method measures the average void fraction of a flow passage cross section by utilizing the fact that the electrical resistance changes when the void fraction of the two-phase flow changes. A two-phase flow sensor using the stylus method utilizes the change in electrical resistance or the change in the optical refractive index. A two-phase flow sensor using ultrasonic waves, laser (light), or radiation such as x-rays or gamma rays measures the two-phase flow by measuring diffraction, scattering, attenuation, and frequency change.

[0034] (Control part C) 5, the hydrogen two-phase flow sensor 16 and the oxygen two-phase flow sensor 17 are connected to the control unit C. Based on the detection values ​​of the hydrogen two-phase flow sensor 16 and the oxygen two-phase flow sensor 17, the control unit C controls the hydrogen switching valve 9 and the oxygen switching valve 11 as follows.

[0035] 3 and 4, when the hydrogen two-phase flow sensor 16 detects a gas-liquid two-phase flow of hydrogen gas and fresh water 4, the control unit C switches the hydrogen switch valve 9 to the side discharging to the sea surface 2, and when the hydrogen two-phase flow sensor 16 detects only hydrogen gas, as shown in Fig. 5, the control unit C switches the hydrogen switch valve 9 to the side leading to the hydrogen expansion turbine 6. This prevents the gas-liquid two-phase flow of hydrogen gas and fresh water 4 from being introduced into the hydrogen expansion turbine 6.

[0036] 3 and 4, when the oxygen two-phase flow sensor 17 detects a gas-liquid two-phase flow of oxygen gas and fresh water 4, the control unit C switches the oxygen switching valve 11 to the side discharging to the sea surface 2, and when the oxygen two-phase flow sensor 17 detects only oxygen gas, as shown in Fig. 5, the control unit C switches the oxygen switching valve 11 to the side leading to the oxygen expansion turbine 7. This prevents the gas-liquid two-phase flow of oxygen gas and fresh water 4 from being introduced into the oxygen expansion turbine 7.

[0037] (Combustor BUR, Gas Turbine 21) As shown in Fig. 5, an exhaust pipe 18 of the hydrogen expansion turbine 6 and an exhaust pipe 19 of the oxygen expansion turbine 7 are connected to a combustor BUR. The combustor BUR combusts the expanded hydrogen gas discharged from the hydrogen expansion turbine 6 and the expanded oxygen gas discharged from the oxygen expansion turbine 7. The combustion gas generated in the combustor BUR is introduced into a gas turbine 21 through an exhaust pipe 20, and the gas turbine 21 is rotated.

[0038] 5 is much larger than the volume of hydrogen gas introduced into the hydrogen expansion turbine 6 (the volume of hydrogen gas generated in the electrolyzer 5 and expanded in response to the water pressure reducing the pressure in the process of rising to sea level 2) and the volume of oxygen gas introduced into the oxygen expansion turbine 7 (the volume of oxygen gas generated in the electrolyzer 5 and expanded in response to the water pressure reducing the pressure in the process of rising to sea level 2). Therefore, the capacity of the gas turbine 21 is larger than the capacity of the hydrogen expansion turbine 6 and the capacity of the oxygen expansion turbine 7.

[0039] As shown in Fig. 5, a third generator G3 driven thereby is connected to the gas turbine 21. Most of the electric power generated in the third generator G3 is transmitted to an electric power consuming area, and a portion is supplied to a battery BAT of the electrolyzer 5. Note that the battery BAT may be supplied with electric power from any one or more of the first to third generators G1 to G3, rather than from all of them.

[0040] (Water volume control valve 22) 5, the water supply line 3 is provided with a water volume control valve 22 for adjusting the amount of fresh water 4 supplied to the electrolyzer 5. By appropriately restricting the amount of fresh water 4 supplied to the electrolyzer 5 by the water volume control valve 22, it is possible to make a state in which only hydrogen gas is present in the portion of the hydrogen line 8 above the sea level 2 and only oxygen gas is present in the portion of the oxygen line 10 above the sea level 2 after a predetermined time has elapsed since the start of electrolysis in the electrolyzer 5.

[0041] 5 is excessive, the amount of fresh water 4 in the gas-liquid two-phase flow of hydrogen gas and fresh water 4 rising in the hydrogen line 8 increases, and if the depth from sea level 2 to the electrolyzer 5, which is the vertical component of the length of the hydrogen line 8, is not deep, the fresh water 4 in the gas-liquid two-phase flow rising in the hydrogen line 8 does not fall sufficiently due to gravity, and some of the fresh water 4 remains in the part of the hydrogen line 8 above the sea level 2. In this case, by appropriately restricting the amount of fresh water 4 supplied to the electrolyzer 5 by the water amount control valve 22 and reducing the amount of hydrogen gas rising in the hydrogen line 8 and fresh water in the gas-liquid two-phase flow of fresh water 4, it is possible to create a state in which only hydrogen gas exists in the part of the hydrogen line 8 above the sea level 2.

[0042] 5, the amount of fresh water 4 in the two-phase gas-liquid flow of oxygen gas and fresh water 4 rising in the oxygen line 10 increases, and if the vertical component of the length of the oxygen line 10, that is, the depth from the sea level 2 to the electrolyzer 5, is not so deep, the fresh water 4 in the two-phase gas-liquid flow rising in the oxygen line 10 does not fall sufficiently due to gravity, and some of the fresh water 4 remains in the part of the oxygen line 10 above the sea level 2. In this case, by appropriately restricting the amount of fresh water 4 supplied to the electrolyzer 5 by the water amount control valve 22 and reducing the amount of oxygen gas rising in the oxygen line 10 and the fresh water in the two-phase gas-liquid flow of fresh water 4, it is possible to make the part of the oxygen line 10 above the sea level 2 contain only oxygen gas.

[0043] As shown in FIG. 5, the water amount adjustment valve 22 is connected to the control unit C. After the power generation system 1 has stabilized after a predetermined time has elapsed since the start of electrolysis by the electrolyzer 5, the control unit C controls the water amount adjustment valve 22 in a direction gradually reducing the flow rate when the hydrogen two-phase flow sensor 16 provided in a portion of the hydrogen line 8 above the sea level 2 detects a two-phase gas-liquid flow of hydrogen gas and fresh water 4, or when the oxygen two-phase flow sensor 17 provided in a portion of the oxygen line 10 above the sea level 2 detects a two-phase gas-liquid flow of oxygen gas and fresh water 4. The throttling control of the water amount adjustment valve 22 is continued thereafter until the hydrogen two-phase flow sensor 16 detects only hydrogen gas and the oxygen two-phase flow sensor 17 detects only oxygen gas, and the opening is maintained when the sensors 16 and 17 detect only hydrogen gas and only oxygen gas, respectively. As a result, after the operation of the power generation system 1 has stabilized, the opening degree of the water flow control valve 22 is controlled to such an opening degree that only hydrogen gas is present in the portion of the hydrogen line 8 above sea level 2, and only oxygen gas is present in the portion of the oxygen line 10 above sea level 2.

[0044] (others) 5, the flow path cross-sectional area of ​​the hydrogen line 8 is set to be twice as large as the flow path cross-sectional area of ​​the oxygen line 10. In other words, when the fresh water 4 supplied to the electrolyzer 5 through the water amount control valve 22 is electrolyzed, twice as much hydrogen gas as oxygen gas is generated according to the reaction formula "2H2O→2H2+O2." Therefore, the flow path cross-sectional area of ​​the hydrogen line 8 is set to be twice as large as the flow path cross-sectional area of ​​the oxygen line 10.

[0045] 5, the dark hatched area X, light hatched area Y, and open area Z in the hydrogen line 8 and the dark hatched area X, light hatched area Y, and open area Z in the oxygen line 10 are generally aligned in the water depth direction, regardless of the degree of opening of the water flow control valve 22. Therefore, power generation by the first generator G1 using the hydrogen expansion turbine 6 and power generation by the second generator G2 using the oxygen expansion turbine 7 can be efficiently achieved simultaneously.

[0046] (Power generation procedure) The power generation procedure of the power generation system 1 according to this embodiment will be described. First, as shown in FIG. 1, fresh water 4 is stored in the water tank 12. An appropriate amount of sodium hydroxide, sulfuric acid, etc. is added to the fresh water 4 to ensure electrical conductivity in the electrolysis device 5. The water volume control valve 22 is opened, the hydrogen switching valve 9 is switched to the sea surface 2 side, and the oxygen switching valve 11 is switched to the sea surface 2 side. Then, the fresh water 4 in the water tank 12 above the sea surface 2 is guided through the water supply line 3 to the electrolysis device 5 on the seabed or in the sea. The fresh water 4 in the electrolysis device 5 moves through the hydrogen line 8 to the hydrogen switching valve 9 above the sea surface 2 and is discharged from the discharge pipe 14 to the sea surface 2, and moves through the oxygen line 10 to the oxygen switching valve 11 above the sea surface 2 and is discharged from the discharge pipe 15 to the sea surface 2.

[0047] Next, as shown in FIG. 2, the hydrogen switching valve 9 is closed, and the oxygen switching valve 11 is closed. As a result, the water supply line 3, the electrolyzer 5, the hydrogen line 8, and the oxygen line 10 are filled with fresh water 4. Next, as shown in FIG. 3, positive and negative voltages are applied from the battery BAT to the anode 5b and cathode 5c of the electrolyzer 5, the hydrogen switching valve 9 is switched to the sea surface 2 side, and the oxygen switching valve 11 is switched to the sea surface 2 side. Then, electrolysis of the fresh water 4 is started in the electrolyzer 5, hydrogen gas is generated from the cathode 5c, and oxygen gas is generated from the anode 5b. The hydrogen gas generated at the cathode 5c entrains the fresh water 4 in the electrolyzer 5 and the fresh water 4 in the hydrogen line 8, and rises in the hydrogen line 8 as a gas-liquid two-phase flow, and is discharged to the sea surface 2 from the hydrogen switching valve 9 above the sea surface 2 through the discharge pipe 14. The oxygen gas generated at the anode 5b entrains the fresh water 4 in the electrolysis device 5 and the fresh water 4 in the oxygen line 10, forming a gas-liquid two-phase flow that rises up the oxygen line 10 and is discharged to the sea surface 2 through the oxygen switching valve 11 above the sea surface 2 and the exhaust pipe 15.

[0048] Here, as shown in FIG. 3, immediately after the start of electrolysis, the gas-liquid two-phase flow of hydrogen gas and fresh water 4 rising in the hydrogen line 8 is generally dark hatched X, with a high proportion of liquid (fresh water 4). After a certain amount of time has passed, as shown in FIG. 4, the fresh water 4 in the gas-liquid two-phase flow of hydrogen gas and fresh water 4 rising in the hydrogen line 8 descends due to gravity acting on the fresh water 4, so that the proportion of liquid (fresh water 4) remains dark hatched with a high proportion in the hydrogen line 8 from the electrolysis device 5 to the sea level 2, but the proportion of liquid (fresh water 4) is light hatched Y, with a low proportion in the hydrogen line 8 from about halfway up to the sea level 2. After a certain amount of time has passed, the liquid (fresh water 4) in the gas-liquid two-phase flow continues to descend due to gravity, and as shown in FIG. 5, the hydrogen line 8 becomes dark hatched X, light hatched Y, and open Z from the bottom, with only hydrogen gas present in the part of the hydrogen line 8 above the sea level 2. The same is true for the gas-liquid two-phase flow of oxygen gas and fresh water 4 ascending in the oxygen line 10.

[0049] As shown in Fig. 5, in this state, when the hydrogen two-phase flow sensor 16 provided in the hydrogen line 8 above sea level 2 detects only hydrogen gas, the control unit C switches the hydrogen switch valve 9 to the side leading to the hydrogen expansion turbine 6. This causes the hydrogen expansion turbine 6 to be driven by hydrogen gas, and the first generator G1 generates electricity. Also, when the oxygen two-phase flow sensor 17 provided in the oxygen line 10 above sea level 2 detects only oxygen gas, the control unit C switches the oxygen switch valve 11 to the side leading to the oxygen expansion turbine 7. This causes the oxygen expansion turbine 7 to be driven by oxygen gas, and the second generator generates electricity.

[0050] As shown in Fig. 5, the expanded hydrogen gas discharged from the hydrogen expansion turbine 6 and the expanded oxygen gas discharged from the oxygen expansion turbine 7 are guided to the combustor BUR and combusted. The combustion gas generated in the combustor BUR is guided to the gas turbine 21, which is rotated and drives the third generator G3 to generate electricity. Most of the electricity generated by the first, second and third generators G1, G2 and G3 is transmitted to power consumption areas, and a portion is supplied to the battery BAT of the electrolyzer 5 and used to operate the electrolyzer 5.

[0051] (Action and effect) As shown in FIG. 3, fresh water 4 is supplied from above the sea surface 2 through a water supply line 3 to the seabed or underwater at a predetermined depth, and when electrolysis of the fresh water 4 begins in an electrolysis device 5 on the seabed or underwater, hydrogen gas and oxygen gas are generated.

[0052] As shown in Figs. 3 and 4, hydrogen gas generated in the electrolyzer 5 rises from the electrolyzer 5 through the hydrogen line 8, and expands as the pressure decreases as the water depth becomes shallower. The fresh water 4 in the electrolyzer 5 and the fresh water 4 in the hydrogen line 8 are entrained in the rising hydrogen gas, so that a two-phase gas-liquid flow of hydrogen gas and fresh water 4 rises in the hydrogen line 8. Here, the fresh water 4 in the two-phase gas-liquid flow of hydrogen gas and fresh water 4 rising in the hydrogen line 8 is subjected to a downward force due to gravity acting on the fresh water 4. For this reason, immediately after the start of electrolysis, as shown in Figs. 3 and 4, a two-phase gas-liquid flow of hydrogen gas and fresh water 4 exists in the part of the hydrogen line 8 above the sea level 2, but after a certain time has passed since the start of electrolysis, as shown in Fig. 5, only hydrogen gas exists in the part of the hydrogen line 8 above the sea level 2.

[0053] The hydrogen switching valve 9 provided in the hydrogen line 8 above the sea level 2 discharges the gas-liquid two-phase flow of hydrogen gas and fresh water 4 to the sea level 2 when the gas-liquid two-phase flow is present in the hydrogen line 8 above the sea level 2 as shown in Figs. 3 and 4, and guides the hydrogen gas to the hydrogen expansion turbine 6 when only hydrogen gas is present in the hydrogen line 8 above the sea level 2 as shown in Fig. 5. As a result, only hydrogen gas is guided to the hydrogen expansion turbine 6, and a gas-liquid two-phase flow of hydrogen gas and fresh water 4 is not guided. This makes it possible to avoid damage to the hydrogen expansion turbine 6 caused by the gas-liquid two-phase flow being guided to the hydrogen expansion turbine 6, and makes it possible to appropriately recover the expansion energy of the hydrogen gas as it rises from the seabed or underwater to the sea surface. For example, if the electrolyzer 5 is installed on the seabed at a depth of 1,500 m, the hydrogen gas produced in the electrolyzer 5 will be subjected to a pressure of 150 atmospheres. When the hydrogen gas passes through the hydrogen line 8 and rises to the sea surface 2, its volume will expand by 150 times, and the expansion energy can be appropriately recovered by the hydrogen expansion turbine 6.

[0054] Similarly, as shown in Figs. 3 and 4, oxygen gas generated in the electrolyzer 5 rises through the oxygen line 10 from the electrolyzer 5, and expands as the water depth decreases, and the fresh water 4 in the electrolyzer 5 and the fresh water 4 in the oxygen line 10 are entrained in the rising oxygen gas, so that a two-phase gas-liquid flow of oxygen gas and fresh water 4 rises in the oxygen line 10. Here, the fresh water 4 in the two-phase gas-liquid flow of oxygen gas and fresh water 4 rising in the oxygen line 10 is subjected to a downward force due to gravity acting on the fresh water 4. Therefore, immediately after the start of electrolysis, as shown in Figs. 3 and 4, a two-phase gas-liquid flow of oxygen gas and fresh water 4 exists in the part of the oxygen line 10 above the sea level 2, but after a certain time has elapsed since the start of electrolysis, only oxygen gas exists in the part of the oxygen line 10 above the sea level 2, as shown in Fig. 5.

[0055] The oxygen switching valve 11 provided in the oxygen line 10 above the sea level 2 discharges the gas-liquid two-phase flow of oxygen gas and fresh water 4 to the sea level 2 when the gas-liquid two-phase flow of oxygen gas and fresh water 4 is present in the oxygen line 10 above the sea level 2 as shown in Figs. 3 and 4, and guides the oxygen gas to the oxygen expansion turbine 7 when only oxygen gas is present in the oxygen line 10 above the sea level 2 as shown in Fig. 5. As a result, only oxygen gas is guided to the oxygen expansion turbine 7, and the gas-liquid two-phase flow of oxygen gas and fresh water 4 is not guided. This makes it possible to avoid damage to the oxygen expansion turbine 7 caused by the gas-liquid two-phase flow being guided to the oxygen expansion turbine 7, and makes it possible to appropriately recover the expansion energy of the gas when the oxygen gas rises from the seabed or underwater to the sea level 2. For example, if the electrolyzer 5 is installed on the seabed at a depth of 1,500 m, the oxygen gas generated in the electrolyzer 5 will be subjected to a pressure of 150 atmospheres. When the oxygen gas rises to the sea surface 2 through the oxygen line 10, its volume will expand 150 times, and the expansion energy can be appropriately recovered by the oxygen expansion turbine 7.

[0056] Furthermore, as shown in FIG. 5, hydrogen gas generated in electrolyzer 5 placed on the seabed or underwater is conducted through hydrogen line 8 to hydrogen expansion turbine 6 located above sea level 2, and oxygen gas generated in electrolyzer 5 is conducted through oxygen line 10 to oxygen expansion turbine 7 located above sea level 2. Therefore, hydrogen gas and oxygen gas do not become mixed in hydrogen expansion turbine 6 and oxygen expansion turbine 7, resulting in high safety.

[0057] Thus, the power generation system 1 according to this embodiment can appropriately recover the gas expansion energy generated when the hydrogen gas and oxygen gas generated by electrolyzing fresh water 4 in the seabed or subsea electrolyzer 5 rise to the sea surface 2, and is highly safe. In addition, the expanded hydrogen gas exhausted from the hydrogen expansion turbine 6 and the expanded oxygen gas exhausted from the oxygen expansion turbine 7 are combusted in the combustor BUR, and the gas turbine 21 is rotationally driven by the combustion gas, so that the combustion energy generated by burning the hydrogen gas and oxygen gas generated in the electrolyzer 5 can also be recovered.

[0058] The above describes a preferred embodiment of the present invention with reference to the attached drawings. However, it goes without saying that the present invention is not limited to the above-described embodiments, and various modified or altered examples within the scope of the claims also fall within the technical scope of the present invention.

[0059] 5 may be omitted, and the switching of the hydrogen switching valve 9, the switching of the oxygen switching valve 11, and the adjustment of the opening of the water volume control valve 12 may be performed manually. Also, by setting the cross-sectional area of ​​the water supply port of the water supply line 3 to the electrolyzer 5 to an appropriate value, if only hydrogen gas is present in the portion of the hydrogen line 8 above the sea level 2 and only oxygen gas is present in the portion of the oxygen line 10 above the sea level 2 after a predetermined time has elapsed since the start of electrolysis of fresh water 4 by the electrolyzer 5 and the power generation system 1 has stabilized, the water volume control valve 22 may be omitted. [Industrial Applicability]

[0060] INDUSTRIAL APPLICABILITY The present invention can be used in a power generation system that generates power by utilizing hydrogen gas and oxygen gas generated by electrolysis of water. [Explanation of symbols]

[0061] 1. Power generation system 2 sea level 3. Water supply line 4. Fresh Water 5. Electrolysis Apparatus 6 Hydrogen expansion turbine 7 Oxygen expansion turbine 8 Hydrogen Line 9 Hydrogen switching valve 10 Oxygen Line 11 Oxygen switching valve 16 Hydrogen two-phase flow sensor 17 Oxygen two-phase flow sensor 21 Gas Turbine 22 Water volume control valve C control section BUR Combustor G1 First generator G2 Second generator G3 Third generator

Claims

1. A power generation system comprising: a water supply line for supplying fresh water from above the sea surface to the seabed or underwater at a predetermined depth; an electrolysis device connected to the water supply line and placed on the seabed or underwater for electrolyzing the fresh water supplied from the water supply line to produce hydrogen gas and oxygen gas; a hydrogen expansion turbine rotated and driven by the hydrogen gas produced by the electrolysis device and placed above the sea surface; and an oxygen expansion turbine rotated and driven by the oxygen gas produced by the electrolysis device and placed above the sea surface, a hydrogen line connecting the electrolyzer and the hydrogen expansion turbine and extending from the seabed or subsea to above the sea level; and a hydrogen switching valve provided in a portion of the hydrogen line above the sea level, for discharging a two-phase gas-liquid flow of hydrogen gas and fresh water to the sea surface when the two-phase gas-liquid flow is present in the hydrogen line, and for directing the hydrogen gas to the hydrogen expansion turbine when only hydrogen gas is present in the hydrogen line. a switching valve provided in a portion of the oxygen line above the sea surface for discharging a two-phase gas-liquid flow of oxygen gas and fresh water to the sea surface when the two-phase flow is made of oxygen gas and fresh water, and for directing the oxygen gas to the oxygen expansion turbine when only oxygen gas is present in the oxygen line.

2. a hydrogen two-phase flow sensor is provided in a portion of the hydrogen line above the sea level to detect whether a gas-liquid two-phase flow of hydrogen gas and fresh water is present in the hydrogen line or whether only hydrogen gas is present; an oxygen two-phase flow sensor is provided in a portion of the oxygen line above the sea level for detecting whether a gas-liquid two-phase flow of oxygen gas and fresh water exists in the oxygen line or whether only oxygen gas exists; a control unit connected to the hydrogen two-phase flow sensor and the oxygen two-phase flow sensor, and controlling the hydrogen switching valve and the oxygen switching valve, The control unit when the hydrogen two-phase flow sensor detects a gas-liquid two-phase flow of hydrogen gas and fresh water, the hydrogen switching valve is switched to the side discharging to the sea surface, and when the hydrogen two-phase flow sensor detects only hydrogen gas, the hydrogen switching valve is switched to the hydrogen expansion turbine side; 2. The power generation system according to claim 1, wherein the oxygen switching valve is switched to a side discharging to the sea surface when the oxygen two-phase flow sensor detects a gas-liquid two-phase flow of oxygen gas and fresh water, and the oxygen switching valve is switched to the oxygen expansion turbine side when the oxygen two-phase flow sensor detects only oxygen gas.

3. a combustor that combusts the hydrogen gas discharged from the hydrogen expansion turbine and the oxygen gas discharged from the oxygen expansion turbine; 3. The power generation system according to claim 1, further comprising: a gas turbine that is rotationally driven by the combustion gas generated in the combustor.

4. 4. The power generation system according to claim 3, further comprising a water flow control valve provided in the water supply line for controlling the amount of fresh water supplied to the electrolyzer.

5. 5. The power generation system according to claim 4, wherein the flow cross-sectional area of ​​the hydrogen line is twice as large as the flow cross-sectional area of ​​the oxygen line.

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