Wave Energy Conversion Device

Abstract

To provide a wave power energy conversion device which has high power generation efficiency and high durability, is easy to install on a sea bottom, and can be manufactured inexpensively.SOLUTION: A wave power energy conversion device 1a comprises a first pressure-resistant vessel 2 and a second pressure-resistant vessel 3 which are composed of long-sized hollow members, and a connecting pipe 4 having a submerged power generator incorporated therein and provided with flanges 4a, 4b at opposite ends. The first pressure-resistance vessel 2 and the second pressure-resistance vessel 3 are provided with flow-in ports 2e to 2h and flow-out ports 3a to 3h, respectively, along a longitudinal direction. First check valves 5 are installed at the flow-in ports 2e to 2h of the first pressure-resistance vessel 2, and second check valves 6 are installed at the flow-out ports 3e to 3h of the second pressure-resistance vessel 3.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a device for generating electricity by utilizing the power of waves that occur naturally in the sea, and more particularly to a wave energy converter capable of efficiently converting wave energy into electrical energy. [Background technology]

[0002] Natural energy is called clean energy because it does not emit carbon dioxide when used for power generation and places less of a burden on the global environment than using traditional fossil fuels. Solar and wind power are generally known as natural energy sources, but they have the problem of being dependent on the time of day and weather. In contrast, wave power can generate large amounts of energy in a relatively stable manner, and has been attracting particular attention in recent years. The main types of wave power generation systems are known to be oscillating water column type, movable object type, and overtopping type. The oscillating water column type wave power generation system has an air chamber that allows seawater to flow in, and generates electricity by rotating a turbine with the air flow that flows in and out of an opening in the air chamber as the sea surface moves up and down. This type of structure has the advantage that it can be installed near energy demand areas, and has excellent durability because it has no moving parts. On the other hand, there is a problem that the efficiency of the turbine is low, and in shallow sea areas, a lot of energy is lost before the waves reach the device. A typical movable object type wave power generation system has a pendulum pressure plate with its free end located below the sea surface and its fixed end located above the sea surface, and the kinetic energy generated by the pressure plate swaying with the waves is converted into electrical energy. This type of structure has the advantage of not requiring a turbine, but has the problem of frequent breakdowns because the pendulum pressure plate is directly subjected to large forces from the waves. Most other movable object type wave power generation systems also have the problem of equipment breakdowns. The wave-overtopping wave power generation system is designed to generate electricity by rotating a turbine using the difference in height between the water surface of a reservoir and the sea surface. This type of structure has good power generation efficiency because there is little fluctuation in power generation over time, but the problem is that it is difficult to change the height of the overtopping breakwater, which limits the energy gain.

[0003] As an example of a power generation device having a structure different from the oscillating water column type, movable object type, and overtopping type wave power generation systems that have the above-mentioned problems, Patent Document 1 describes an invention titled "Device for extracting energy from waves," which relates to a device that extracts energy from water surface waves by using the flow of water from a high-level water reservoir to a low-level water reservoir to drive a turbine for generating electricity. The invention described in Patent Document 1 comprises a first check valve provided on the side wall of the high-level reservoir which allows water to pass into the high-level reservoir while preventing water from returning from the high-level reservoir, and a second check valve provided on the side wall of the low-level reservoir which allows water to pass from the low-level reservoir while preventing water from returning to the low-level reservoir. This creates a flow of water from the high-level reservoir to the low-level reservoir, and this water flow drives a turbine. Such a structure has the advantage that it is less affected by wave periods than conventional power generation devices designed to extract energy from water waves.

[0004] Additionally, Patent Document 2 describes an invention titled a "wave energy conversion device" that converts wave energy into other forms of energy, such as electrical energy, by using a structure that allows water to pass through in only one direction, without any moving parts such as flaps or hinge shafts. The invention described in Patent Document 2 comprises a water chamber having a water inlet chamber and a water outlet chamber, the inlet chamber having a side wall with a water inlet opening whose outer opening area is larger than the inner opening area, and the outlet chamber having a side wall with a water outlet opening whose inner opening area is larger than the outer opening area, a water passage section is formed between the inlet chamber and the outlet chamber, and a turbine arranged in this water passage section is driven by the water flow that passes through the water passage section and heads toward the outlet chamber. With this structure, the water inlet opening provided in the side wall of the inlet chamber and the water outlet opening provided in the side wall of the outlet chamber allow water to pass through in only one direction, thereby significantly improving durability compared to conventional devices in which moving parts such as flaps and hinge shafts are provided in the side walls. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 52-151434 [Patent Document 2] JP 2018-91254 A Summary of the Invention [Problem to be solved by the invention]

[0006] In the invention described in Patent Document 1, each check valve is equipped with a flap, and the flap is hinged to a vertical or horizontal axis, and a part of the high-level water reservoir is arranged above the sea level. Since the displacement of water particles and the flow speed of waves are greatest near the water surface, in the invention described in Patent Document 1 equipped with the above structure, the high-level water reservoir may be damaged by the large force of waves during high waves. In addition, the water reservoir is large in size, making it difficult to moor it to the seabed. Furthermore, the water pressure acting on the flap, which is activated by wave movement, is not uniform in the hinge axis direction, generating a torsional force on the flap and the hinge axis, which causes problems in terms of durability.

[0007] In addition, in the invention described in Patent Document 2, the inflow and outflow openings provided in the inflow and outflow chambers are structured to limit the flow of water to one direction by changing the size of the opening area inside and outside the inflow and outflow chambers, but unlike a check valve, it is not possible to completely prevent backflow, so there is a possibility that the amount of water flowing from the inflow chamber to the outflow chamber cannot be sufficiently secured, resulting in low power generation efficiency. In addition, since the inflow and outflow chambers are structured so that the side walls are directly subjected to the force of waves, there is a risk of damage due to the large force from the waves during high waves. Furthermore, since the inflow and outflow chambers are large-scale structures, there is a problem that it is not easy to moor them to the seabed.

[0008] The present invention has been made in response to the above-mentioned problems in the prior art, and aims to provide a wave energy conversion device that has high power generation efficiency, excellent durability, is easy to install on the seabed, and can be manufactured inexpensively. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, the wave energy conversion device of the first invention comprises a first pressure-resistant vessel and a second pressure-resistant vessel each consisting of a long hollow member, a first check valve installed at each of a plurality of inlets provided along the longitudinal direction on the top or side of the first pressure-resistant vessel, a second check valve installed at each of a plurality of outlets provided along the longitudinal direction on the top or side of the second pressure-resistant vessel, and an underwater generator installed inside the first pressure-resistant vessel or the second pressure-resistant vessel, wherein the first pressure-resistant vessel and the second pressure-resistant vessel are connected to each other so that water within the hollow portions can move, and the first check valve only allows water to flow into the first pressure-resistant vessel, and the second check valve only allows water to flow out of the second pressure-resistant vessel. When the first invention having such a structure is installed on the seabed near the shore so that its longitudinal direction is parallel to the traveling direction of the waves, if the length of the section in which the first check valve and the second check valve are provided in the first pressure vessel and the second pressure vessel are respectively longer than the wavelength, seawater flows into the first pressure vessel from an inlet located directly below a place where the piezo head of the sea level is higher than the piezo head of the mean sea level plus alpha, moves into the second pressure vessel, and flows out of the second pressure vessel from an outlet located directly below a place where the piezo head of the sea level is lower than the piezo head of the mean sea level minus alpha. At this time, since the sea level changes continuously due to the movement of the waves (especially the movement of the traveling waves), the inlet through which seawater flows into the first pressure vessel and the outlet through which seawater flows out of the second pressure vessel alternate in sequence without interruption. As a result, the first invention has the effect that a water flow in a fixed direction is always generated to rotate the rotor of the underwater generator. In addition, since the pressure inside the first pressure vessel and the second pressure vessel, and therefore the difference in the piezoelectric head inside both pressure vessels, does not change much during operation of the device, there is an effect that the rotation speed of the underwater generator changes little. Furthermore, since the underwater generator is installed inside the first pressure vessel or the second pressure vessel, there is an effect that it is less prone to malfunction. And, since the entire device is structured with members having hollow parts connected together, there is an effect that it is lightweight and easy to install and remove.

[0010] The second invention is characterized in that, in the first invention, the first pressure-resistant vessel and the second pressure-resistant vessel are connected by a connecting pipe, and the underwater generator is installed inside the connecting pipe instead of the first pressure-resistant vessel or the second pressure-resistant vessel. In the first invention, when repairing or replacing the underwater generator, the first or second pressure vessel must be pulled up from the seabed to land, whereas in the second invention, the underwater generator is installed inside the connecting pipe, so it is sufficient to pull up only the connecting pipe with the underwater generator installed inside. Therefore, maintenance work on the underwater generator is much easier in the second invention than in the first invention.

[0011] A third aspect of the present invention is the second aspect of the present invention, characterized in that the connecting pipe has flexibility. In the third invention, since the first and second pressure vessels are connected by a flexible connecting pipe, it is possible to freely change the arrangement of the first and second pressure vessels (the positional relationship between them) to a certain extent so as to reduce the influence of the unevenness of the seabed. Therefore, in addition to having the effect of the second invention, the third invention has the effect of having fewer restrictions on the installation location.

[0012] A fourth invention is characterized in that, in any one of the first to third inventions, the first pressure-resistant vessel and the second pressure-resistant vessel are arranged parallel to each other. In any of the first to third inventions, if a space with few projections and recesses and sufficient vertical length cannot be secured on the seabed, it is difficult to install the first and second pressure vessels in a straight line on the seabed. In contrast, if the first and second pressure vessels are arranged parallel to each other, they can be installed even if the space does not have a sufficient vertical length. Therefore, in the fourth invention, in addition to the effect of any of the first to third inventions, the effect of fewer restrictions on the installation location is further exhibited.

[0013] The fifth invention is characterized in that, in the second or third invention, the first pressure-resistant vessel and the second pressure-resistant vessel are arranged parallel to each other, and opposing sides of the first pressure-resistant vessel and the second pressure-resistant vessel are connected by a connecting pipe. In the fifth invention, in which the opposing sides of the first and second pressure vessels arranged in parallel are connected by a connecting pipe, the connection point of the connecting pipe can be changed along the longitudinal direction of the first and second pressure vessels, so that the connecting pipe can be installed in a location on the seabed with few irregularities. Therefore, in addition to the effects of the second and third inventions, the fifth invention further exhibits the effect of fewer restrictions on installation locations.

[0014] A sixth invention is characterized in that, in any one of the first to fifth inventions, a support part is provided for supporting the first pressure-resistant vessel and the second pressure-resistant vessel. The sixth invention has the effect of easily ensuring the horizontal state of the first pressure-resistant vessel and the second pressure-resistant vessel by adjusting the height of the support part, in addition to the effect of any one of the first to fifth inventions. Effect of the Invention

[0015] According to the first invention, when the first pressure vessel and the second pressure vessel are installed near the shore and the length of the section where the first check valve and the second check valve are provided is longer than the wavelength, and the vessel is installed on the seabed with its longitudinal direction parallel to the direction of wave movement, a water flow in a fixed direction that rotates the rotor of the underwater generator is always generated. In this installation form, the fixing of the device, which is commonly required for wave energy conversion devices, can be achieved very easily. Furthermore, since the pressure inside the first pressure vessel and the second pressure vessel does not change much during operation of the device and the rotation speed of the underwater generator also changes little, according to the first invention, high power generation efficiency can be expected. Furthermore, since the underwater generator rotates due to the flow of water, which has a density much higher than that of air, the power generation capacity is significantly higher than that of a system using an air turbine. In other words, according to the first invention, it is not necessary to use an expensive generator with a high power generation capacity, and therefore it can be manufactured inexpensively. Furthermore, the first invention has excellent durability because the entire device including the underwater generator is less likely to break down. In addition, since the installation and removal work is easy, the costs required for installation, removal and maintenance are reduced.

[0016] According to the second invention, since maintenance work is easy, in addition to providing the effect of the first invention, there is also an effect that the cost required for maintenance is reduced.

[0017] In the third invention, the arrangement of the first and second pressure vessels (the positional relationship between them) can be freely changed to some extent so as to reduce the effect of the unevenness of the seabed. Therefore, according to the third invention, in addition to having the effect of the second invention, the effect of reducing the cost required for installation is further exhibited.

[0018] According to the fourth invention, in addition to having the effects of any one of the first to third inventions, the effect of reducing installation costs is further enhanced since there are fewer restrictions on the installation location.

[0019] According to the fifth invention, in addition to having the effects of the second or third invention, there are fewer restrictions on the installation location, and therefore the effect of reducing installation costs is further exerted.

[0020] In the sixth invention, the horizontal state of the first pressure vessel and the second pressure vessel can be easily ensured by adjusting the length of the support part, and therefore installation is easy. Therefore, according to the sixth invention, in addition to having the effect of any one of the first to fifth inventions, the effect of reducing the cost required for installation is further exhibited. [Brief description of the drawings]

[0021] [Figure 1] (a) and (b) are respectively a plan view and a side view of Example 1 of a wave energy conversion device according to an embodiment of the present invention, and (c) and (d) are respectively enlarged views of the cross sections taken along the arrows AA and BB in FIG. (a). [Diagram 2]1(c) and (d) are plan and side views, respectively, of a base constituting the first check valve and the second check valve shown in FIG. 1(c) and FIG. 1(d), (c) and (d) are plan and oblique views, respectively, of a rubber plate installed on one side of the base, and (e) and (f) are plan views of a pressure plate installed on one side of the rubber plate. [Diagram 3] (a) is a longitudinal cross-sectional view of a connecting pipe with an underwater generator built in, (b) and (c) are front views of a guide vane and a runner vane, respectively, and (d) is a cross-sectional view taken along line CC in (a) of the same figure. [Figure 4] 4 is a graph showing the distribution of piezoelectric heads in various parts of a wave energy converter of the present invention installed on the seabed. [Diagram 5] 1(a) and 1(b) are schematic diagrams showing the wave energy conversion devices shown in FIG. 1(a) and FIG. 1(b) installed on the seabed. [Figure 6] FIG. 2(a) is a plan view of a wave energy conversion device according to a second embodiment of the present invention, and FIG. 2(b) and FIG. 2(c) are schematic side views of the wave energy conversion device shown in FIG. 2(a) installed on the seabed. [Figure 7] FIG. 3(a) is a plan view of a wave energy conversion device according to a third embodiment of the present invention, and FIG. 3(b) and FIG. 3(c) are schematic side views of the wave energy conversion device shown in FIG. 3(a) installed on the seabed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] The structure of the wave energy converter of the present invention and the actions and effects exerted therewith will be specifically described with reference to Figures 1 to 7. In the following description, expressions such as "upper surface" and "lower surface" are used, assuming that the wave energy converter of the present invention is installed on the seabed. In addition, although the specification and drawings of the present application show a structure in which the flanges of the connecting pipe are fixed to the first pressure vessel and the second pressure vessel using bolts, the wave energy converter of the present invention is not limited to such a structure. For example, the connecting pipe may not have a flange, and may be fixed to the first pressure vessel and the second pressure vessel by welding or the like instead of using bolts. EXAMPLES

[0023] Figures 1(a) and 1(b) are respectively a plan view and a side view of the wave energy converter 1a, and Figures 1(c) and 1(d) are respectively enlarged views of the cross sections along the arrows AA and BB in Figure 1(a). Figures 2(a) and 2(b) are respectively a plan view and a side view of the base 7 constituting the first check valve 5 and the second check valve 6 shown in Figures 1(c) and 1(d), and Figures 2(c) and 2(d) are respectively a plan view and a perspective view of a rubber plate 8 installed on one side of the base 7. Figure 2(e) is a plan view of a pressure plate 9 installed on one side of the rubber plate 8, and Figure 2(f) is a plan view of a pressure plate 10 according to a modified example of the pressure plate 9 shown in Figure 2(e). Figure 3(a) is a longitudinal cross-sectional view of the connecting pipe 4 in which the underwater generator 11 is built, Figures 3(b) and 3(c) are front views of the guide vane 15 and runner vane 14, respectively, and Figure 3(d) is a cross-sectional view taken along line CC in Figure 3(a).

[0024] 1(a) and 1(b), only the inner wall surface of the connecting pipe 4 is indicated by a dashed line, and in FIG. 1(b), the positions of the inlets 2e-2h and the outlets 3e-3h are indicated by a dashed line, while the first check valve 5, the second check valve 6, and the underwater generator 11 are omitted. In addition, in FIG. 1(c) and 1(d), the first pressure-resistant vessel 2 and the second pressure-resistant vessel 3 are cut by a plane (transverse section) perpendicular to the longitudinal direction at the location where the inlet 2h and the outlet 3e are provided, but the cross sections at the locations where the other inlets 2e-2g and the outlets 3f-3h are provided have the same structure, so in FIG. 1(c) and 1(d), the inlets 2e-2g and the outlets 3f-3h are indicated in parentheses together with the inlet 2h and the outlet 3e. Furthermore, in order to avoid the drawings becoming complicated, each of the plurality of notches 8a, openings 9a, and small holes 10a is given a reference symbol in FIG. 2(c) to FIG. 2(f). In addition, in Fig. 3(a), only the vertical cross section of the connecting pipe 4 is shown, and the external appearance of the underwater generator 11 installed inside is shown. In Fig. 3(b) and Fig. 3(c), in order to avoid the diagram becoming complicated, only one of the multiple blades 14b, 15a is given a reference number. Furthermore, in Fig. 3(b) to Fig. 3(d), only the outlines of the casings 12a to 12c are shown, and the internal structure is not shown. In Fig. 3(c), the blades 14b are hatched to easily distinguish between the portion where the blades 14b are provided and the portion where the blades 14b are not provided (i.e., the portion between the blades 14b).

[0025] As shown in Fig. 1(a) and Fig. 1(b), the wave energy conversion device 1a includes a first pressure-resistant vessel 2 and a second pressure-resistant vessel 3 made of a long hollow member, and a connecting pipe 4 having an underwater generator 11 (see Fig. 3(a)) built therein and flanges 4a, 4b provided at both ends. In addition, the end 2a of the first pressure-resistant vessel 2 and the end 3a of the second pressure-resistant vessel 3 form a right-angled triangle in which the lower surfaces 2d, 3d of the end 2a, 3a of the second pressure-resistant vessel 3 form one of two sides that sandwich a right angle when viewed from the side, and the flanges 4a, 4b of the connecting pipe 4 are fixed to the end 2b, 3b, respectively, using bolts (not shown). In other words, the first pressure-resistant vessel 2 and the second pressure-resistant vessel 3 are connected via the connecting pipe 4, and water inside the hollow parts 2p, 3p (see Fig. 1(c) and Fig. 1(d)) can move through the connecting pipe 4. The above-mentioned structures at the ends 2a and 3a act to reduce the force parallel to the longitudinal direction that the first pressure-resistant vessel 2 and the second pressure-resistant vessel 3 receive from waves. Furthermore, four inlets 2e-2h and outlets 3e-3h are provided along the longitudinal direction of each of the first pressure-resistant vessel 2 and the second pressure-resistant vessel 3. A first check valve 5 (see FIG. 1(c)) is provided at each of the inlets 2e-2h of the first pressure-resistant vessel 2, and a second check valve 6 (see FIG. 1(d)) is provided at each of the outlets 3e-3h of the second pressure-resistant vessel 3. The first pressure-resistant vessel 2 and the second pressure-resistant vessel 3 may be cylindrical instead of rectangular. The number of inlets provided in the first pressure-resistant vessel 2 and the number of outlets provided in the second pressure-resistant vessel 3 are not limited to four each, and the number can be changed as appropriate. Furthermore, instead of providing the inlets and outlets on the upper surface 2c of the first pressure-resistant vessel 2 and the upper surface 3c of the second pressure-resistant vessel 3, the inlets and outlets can be provided on the side surfaces of the upper surfaces 2c and 3c of the first pressure-resistant vessel 2 and the second pressure-resistant vessel 3, respectively.

[0026] 1(c) and 1(d), the first check valve 5 and the second check valve 6 are equipped with a base 7, a rubber plate 8 installed on one side of the base 7 with its raised center portion facing the inside of the base 7, and a pressing plate 9 installed on one side of the rubber plate 8. In other words, the first check valve 5 and the second check valve 6 are structured such that the rubber plate 8 is sandwiched between the base 7 and the pressing plate 9 from above and below. The first check valve 5 is installed on the ceiling surface 2q of the hollow portion 2p of the first pressure-resistant vessel 2 so that the surface of the pressing plate 9 not in contact with the rubber plate 8 blocks the inlets 2e to 2h. On the other hand, the second check valve 6 is installed on the ceiling surface 3q of the hollow portion 3p of the second pressure-resistant vessel 3 so that the end of the base 7 not in contact with the rubber plate 8 blocks the outlets 3e to 3h.

[0027] As shown in Fig. 2(a) and Fig. 2(b), the base 7 is made of a cylindrical tube, and the flanges 7a, 7a at both ends are provided with four screw holes 7b at equal intervals in the circumferential direction. As shown in Fig. 2(c) and Fig. 2(d), the rubber plate 8 is circular in plan view with the same outer diameter as the flange 7a of the base 7, and has eight notches 8a of a predetermined length formed radially from the center of the circle, so that the center is raised in side view. Four screw insertion holes 8b are provided at equal intervals in the circumferential direction so as to surround the eight notches 8a. Furthermore, as shown in Fig. 2(e), the pressing plate 9 is circular in plan view with the same outer diameter as the flange 7a of the base 7, and eight openings 9a are provided so as to be point-symmetrical with respect to the center of the circle. Four screw insertion holes 9b are provided at equal intervals in the circumferential direction so as to surround the eight openings 9a. As shown in FIG. 2(f), the pressing plate 10 has a circular shape with an outer diameter equal to that of the flange 7a of the base 7 in plan view, and a large number of small holes 10a are formed in the center by punching, and four screw insertion holes 10b are provided at equal intervals in the circumferential direction so as to surround the portion where the large number of small holes 10a are formed. The screw insertion holes 8b, 9b, and 10b have the same inner diameter, and are formed at positions where a screw (not shown) screwed into the screw hole 7b can be communicated when the rubber plate 8, the pressing plate 9, and the pressing plate 10 are installed on one side of the base 7 in a stacked manner. That is, the rubber plate 8 and the pressing plate 9, or the rubber plate 8 and the pressing plate 10, are structured to be fastened together to the base 7 by using the above-mentioned screw. The opening 9a of the pressing plate 9 and the small holes 10a of the pressing plate 10 function as a water passage when water flows into the inside of the base 7.

[0028] As shown in Figures 3(a) to 3(d), the underwater generator 11 installed inside the connecting pipe 4 includes a generator main body 13 consisting of a stator, rotor, main shaft, etc. (not shown) housed in a casing 12a having a cylindrical shape with one end closed, a runner vane 14 installed upstream of the generator main body 13, and a guide vane 15 installed upstream of the runner vane 14. The outer peripheral surface of the casing 12a of the generator body 13 is fixed to the inner peripheral surface of the connecting pipe 4 via eight ribs 16. A stator arranged to surround the rotor is fixed to the inner peripheral surface of the casing 12a, and the main shaft to which the rotor is attached is rotatably held by a bearing fixed to the casing 12a via a support member. The guide vane 15, also called a guide vane, is used to adjust the amount of water flowing into the runner vane 14 and the direction of the water flow. It is composed of a plurality of vanes 15a, one end of which is fixed to the outer circumferential surface of the casing 12b, which has a cylindrical shape with one end closed, and the other end of which is fixed to the inner circumferential surface of the connecting pipe 4. On the other hand, the runner vane 14 is composed of a reinforcing member 14a made of an annular thin plate material, and a plurality of vanes 14b, one end of which is fixed to the inner circumferential surface of the reinforcing member 14a, and the other end of which is fixed to the outer circumferential surface of the cylindrical casing 12c. Inside the casing 12c, a columnar or cylindrical shaft (not shown) that rotates together with the runner vane 14 is installed, and one end of this shaft is rotatably held by a bearing (not shown) installed inside the casing 12a and is connected to the main shaft via a connector (not shown). The other end of the shaft is rotatably held by a bearing (not shown) installed inside the casing 12b.

[0029] As shown by arrow D in FIG. 3(a), the water that flows into the connecting pipe 4 from the opening 4c on the flange 4a side is rectified by the guide vane 15 and then rotates the blades 14b of the runner vane 14. This rotation causes the main shaft, one end of which is connected to the shaft of the runner vane 14, and the rotor attached to it to rotate. As the rotor rotates, an induced electromotive force is generated in the coil wound around the stator. The water that rotates the runner vane 14 flows toward the rear of the generator body 13 along the outer circumferential surface of the casing 12a, and then flows out of the connecting pipe 4 from the opening 4d on the flange 4b ​​side, as shown by arrow E in FIG. 3(a). Thus, in the underwater generator 11, the water flowing inside the connecting pipe 4 rotates the runner vanes 14, which in turn rotates the rotor, generating electricity. Therefore, in the wave energy conversion device 1a having a structure in which the flanges 4a, 4b of the connecting pipe 4 are connected to the end 2b of the first pressure vessel 2 and the end 3b of the second pressure vessel 3, respectively, it is necessary to generate a water flow that passes from the first pressure vessel 2 through the inside of the connecting pipe 4 toward the second pressure vessel 3.

[0030] Here, the mechanism by which the above-mentioned water current is generated in the wave energy converter 1a will be explained with reference to Figures 4 and 5. Figure 4 is a graph showing the distribution state of the piezoelectric head in each part of the wave energy converter 1a installed on the seabed 17, and Figures 5(a) and 5(b) are schematic diagrams showing the state in which the wave energy converter 1a is installed on the seabed 17. Note that the components shown in Figures 1 to 3 are given the same reference numerals and their explanation will be omitted. The curves in Figure 4 assume that the above waves are sine waves, and the mean water level and wave height are h 0 and H represent the piezoelectric head at each portion on the surface of the wave energy conversion device 1a. Furthermore, the two solid lines above and below the curve represent the piezoelectric heads inside the first pressure vessel 2 and the second pressure vessel 3, respectively. In FIG. 5(b), the solid curve represents the shape of the water surface when the waves generated above the wave energy conversion device 1a installed on the seabed 17 are assumed to be sine waves, and the dashed straight line crossing the curve represents the position of the sea surface (average water level) when no waves are generated. In addition, the downward arrows and the upward arrows in FIG. 5(b) correspond to the flow rate of water passing through the inlets 2f, 2g and the outlets 3e, 3f. That is, the longer arrows indicate a larger flow rate than the shorter arrows. Furthermore, in FIG. 5(b), the positions of the inlets 2e to 2h and the outlets 3e to 3h are shown by dashed lines.

[0031] In Fig. 4, it is assumed that the energy loss of the water flowing against resistance inside the first pressure vessel 2, the second pressure vessel 3, and the connecting pipe 4 during operation of the wave energy conversion device 1a does not change over time, and the effect is represented by α. However, 0<α<1, and the greater the resistance of the above-mentioned water flow, the closer α is to 1, and the smaller the resistance of the above-mentioned water flow, the closer α is to 0. In this case, the piezoelectric heads inside the first pressure vessel 2 and the second pressure vessel 3 are expressed by the following formulas (1) and (2). Furthermore, the height y of the wavefront at a certain time is expressed by formula (3) where L is the wavelength. This shows the distribution of the piezoelectric heads on the surfaces of the first pressure vessel 2 and the second pressure vessel 3. Therefore, water passes through the inlets 2e-2h and the outlets 3e-3h only when formula (4) is satisfied. In other words, among the inlets 2e-2h, if the piezoelectric head on the surface is h 0 Water flows into the first pressure vessel 2 from the portion (between A and B in the figure) where the piezoelectric head at the surface of the outlets 3e to 3h is h 0 Water inside the second pressure-resistant vessel 3 flows out to the outside from the portion where the pressure is equal to or less than -αH / 2 (between CD in the figure).

[0032]

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[0033]

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[0034]

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[0035]

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[0036] If the effective head is ΔH, the gravitational acceleration is g, the density of water is ρ, and the flow rate is Q, the theoretical hydraulic force P is expressed by the following equation (5). In this problem, the effective head ΔH is equal to the difference in piezoelectric head inside the first pressure vessel 2 and the second pressure vessel 3, so by using equations (1) and (2), it can be expressed by equation (6).

[0037]

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[0038]

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[0039] Assuming that the first pressure vessel 2 and the second pressure vessel 3 are cylinders with a radius of R and the length of the section in which the check valves are arranged is L, the ratio of the total area S of the inlets 2e to 2h or the outlets 3e to 3h to the area of ​​the outer circumferential surface of the above section of the first pressure vessel 2 or the second pressure vessel 3 is κ h Then, it is expressed by formula (7). Furthermore, the velocity V of the water passing through the inlets 2e to 2h and the outlets 3e to 3h is expressed by formula (8), and by substituting formula (3) into formula (8), the velocity V can be obtained as formula (9). Furthermore, since the flow rate Q is expressed by formula (10), the theoretical hydraulic power P can be obtained from formulas (5), (6), (7), (9), and (10) as formula (11).

[0040]

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[0041]

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[0042]

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[0043]

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[0045] In formula (11), by setting θ=2πx / L and differentiating both sides, we obtain formula (12). Using formula (12), formula (11) can be expressed as formula (13) below.

[0046]

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[0047]

number

[0048] Since waves change direction depending on the topography of the ocean floor, waves near the coast move almost perpendicular to the coastline without being affected by the direction of movement offshore. In addition, near the quay, the vertical movement of the water increases as the horizontal movement of the water is suppressed. Therefore, as shown in FIG. 5(a), the wave energy conversion device 1a is installed on the ocean floor 17 near the coast so that its longitudinal direction is parallel to the direction of wave movement. However, the first pressure vessel 2 and the second pressure vessel 3 are formed so that the length of the section in which the first check valve 5 and the second check valve 6 are installed, respectively, is longer than the wavelength. In the wave energy converter 1a shown in FIG. 5(a), as described with reference to FIG. 4, among the inlets 2e to 2h, the piezoelectric head on the surface of the first pressure vessel 2 is h 0 Water flows into the first pressure vessel 2 from the portion (between A and B in FIG. 4) where the piezoelectric head on the surface of the second pressure vessel 3 is h 0 Water inside the second pressure vessel 3 flows out from the portion where the difference is -αH / 2 or less (between C and D in FIG. 4). If we consider the case where α is infinitely close to 0, among the inlets 2e to 2h, the piezoelectric head on the surface of the first pressure vessel 2 is h 0 In the case of FIG. 5(b), the water flows into the first pressure vessel 2 from the inlets 2f and 2g located directly below the point where the water level shown by the solid line is higher than the average water level shown by the dashed line. Also, when the piezoelectric head on the surface of the second pressure vessel 3 is h 0 In the case of Figure 5(b), this corresponds to outlets 3e and 3f located directly below the point where the sea level shown by the solid line is lower than the average sea level shown by the dashed line. That is, in the wave energy converter 1a shown in Figures 5(a) and 5(b), seawater flows into the first pressure vessel 2 from the inlets 2f and 2g, moves further into the second pressure vessel 3 through the connecting pipe 4 as shown by the arrow F, and then flows out of the second pressure vessel 3 from the outlets 3e and 3f. At this time, since the water level of the sea surface changes continuously due to the movement of waves (particularly the movement of progressive waves), the inlet through which seawater flows into the first pressure vessel 2 and the outlet through which seawater flows out of the second pressure vessel 3 are switched in sequence without interruption. As a result, a water flow in a fixed direction that rotates the rotor of the underwater generator 11 is always generated inside the connecting pipe 4 as shown by the arrow F. In addition, since the pressure inside the first pressure vessel 2, the second pressure vessel 3, and the connecting pipe 4 does not change much during operation of the device, the rotation speed of the underwater generator 11 changes little. Furthermore, since the underwater generator 11 is installed inside the connecting pipe 4, it is unlikely to break down. And since the entire device is structured by connecting members having hollow portions 2p and 3p, it is lightweight and easy to install and remove. And, since the first pressure vessel 2 and the second pressure vessel 3 are arranged in a straight line in the wave energy conversion device 1a, it is possible to install them on the seabed so that their longitudinal directions are parallel to the direction of wave travel. In this case, since the entire device is unlikely to receive horizontal forces from the waves, it is stable when installed on the seabed and unlikely to break down.

[0049] The pressure inside the first pressure vessel 2, the second pressure vessel 3, and the connecting pipe 4 does not change much during operation of the device, and the rotation speed of the underwater generator 11 also changes little, so that the wave energy converter 1a can be expected to generate power with high efficiency. In addition, the underwater generator 11 rotates by the flow of water, which has a much higher density than air, so the power generation capacity is significantly higher than that of a system using an air turbine. In other words, the wave energy converter 1a does not need to use an expensive generator with a high power generation capacity, so it can be manufactured at low cost. Furthermore, the wave energy converter 1a has excellent durability because the entire device including the underwater generator 11 is unlikely to break down. In addition, since the installation and removal work is easy, the wave energy converter 1a reduces the costs required for installation, removal, and maintenance. EXAMPLES

[0050] FIG. 6(a) is a plan view of the wave energy converter 1b, and FIG. 6(b) and FIG. 6(c) are schematic diagrams showing the state in which the wave energy converter 1b is installed on the seabed 17, as seen from the side. FIG. 6(b) shows only the outline of the connecting pipe 4. The same reference numerals are used for the components shown in FIG. 1 to FIG. 5, and the description thereof is omitted. FIG. 6(a) corresponds to FIG. 1(a) showing the wave energy converter 1a, and FIG. 6(b) and FIG. 6(c) correspond to FIG. 5(b). That is, the solid curves shown in FIG. 6(b) and FIG. 6(c) show the shape of the water surface when the waves generated above the wave energy converter 1b installed on the seabed 17 are assumed to be sine waves, and the dashed lines show the position of the sea surface (mean water level) when no waves are generated. The downward arrows in Fig. 6(b) and the upward arrows in Fig. 6(c) correspond to the flow rates of water passing through the inlets 2g, 2h and the outlets 3e, 3f, respectively. That is, longer arrows indicate a higher flow rate than shorter arrows. Note that in Fig. 6(a), only the inner wall surface of the connecting pipe 4 is shown by a dashed line, while in Fig. 6(b) and Fig. 6(c), the positions of the inlets 2e-2h and the outlets 3e-3h are shown by dashed lines, respectively.

[0051] The wave energy conversion device 1b has a structure in which the sides of the first pressure-resistant vessel 2 and the second pressure-resistant vessel 3 are connected to each other via a connecting pipe 4, as shown in Figure 6(a), instead of the end 2b of the first pressure-resistant vessel 2 and the end 3b of the second pressure-resistant vessel 3 being connected to each other via a connecting pipe 4 in the wave energy conversion device 1a of Figure 1(a). In the wave energy converter 1b, as in the case of the wave energy converter 1a described with reference to FIG. 5(b), among the inlets 2e to 2h, the piezoelectric head on the surface of the first pressure vessel 2 is h 0 In the case of FIG. 6(b), the water flows into the first pressure vessel 2 from the part where the piezoelectric head on the surface of the second pressure vessel 3 is larger than h. In the case of FIG. 6(b), the inlets 2g and 2h located directly below the point where the sea level indicated by the solid curve is higher than the average sea level indicated by the dashed line correspond to these inlets. Among the outlets 3e to 3h, the outlets 3e to 3h located directly below the point where the piezoelectric head on the surface of the second pressure vessel 3 is larger than h 0 Water flows out of the second pressure vessel 3 from a portion smaller than the diameter of the second pressure vessel 3. In the case of Fig. 6(c), this corresponds to outlets 3e and 3f located directly below the point where the sea level indicated by the solid curve is lower than the average sea level indicated by the dashed line. That is, in the wave energy converter 1b in the state shown in Fig. 6(b) and Fig. 6(c), seawater flows into the first pressure vessel 2 from the inlets 2g and 2h, moves into the second pressure vessel 3 through the connecting pipe 4 as shown by the arrow G, and then flows out of the second pressure vessel 3 from the outlets 3e and 3f. In this case, the water level of the sea surface changes continuously due to the movement of the waves, so that the inlet through which seawater flows into the first pressure vessel 2 and the outlet through which seawater flows out of the second pressure vessel 3 are switched in sequence without interruption. As a result, a water flow with a fixed direction that rotates the rotor of the underwater generator 11 is always generated inside the connecting pipe 4 as shown by the arrow G in Fig. 6(a). Therefore, the effect based on such an action is exerted in the wave energy converter 1b as in the case of the wave energy converter 1a.

[0052] If there are few projections and recesses and it is not possible to secure a space having a sufficient vertical length, it is difficult to install the first pressure vessel 2 and the second pressure vessel 3 arranged in a straight line on the seabed 17 as in the wave energy conversion device 1a. In contrast, if the first pressure vessel 2 and the second pressure vessel 3 are arranged parallel to each other as in the wave energy conversion device 1b, it may be possible to install them even if the space does not have a sufficient vertical length. Even if the first pressure vessel 2 and the second pressure vessel 3 are arranged parallel to each other, when the ends 2b, 3b of the first pressure vessel 2 and the second pressure vessel 3 are connected by the connecting pipe 4, installation on the seabed 17 may be difficult due to installation space restrictions. In contrast, when the connecting pipe 4 is connected to the side surfaces of the first pressure vessel 2 and the second pressure vessel 3 arranged in parallel, as in the wave energy conversion device 1b, the connection point of the connecting pipe 4 can be changed along the longitudinal direction of the first pressure vessel 2 or the second pressure vessel 3, so that it is possible to install the connecting pipe 4 in a place where the seabed is less uneven. In this way, according to the wave energy conversion device 1b, there are few restrictions on the installation location, and therefore the cost required for installation is reduced. EXAMPLES

[0053] FIG. 7(a) is a plan view of the wave energy converter 1c, and FIG. 7(b) and FIG. 7(c) are schematic diagrams showing the state in which the wave energy converter 1c is installed on the seabed 17, as seen from the side. In FIG. 7(a), the contour line of the underwater generator 11 is shown by a dashed line. The same reference numerals are used for the components shown in FIG. 1 to FIG. 6, and the description thereof is omitted. Furthermore, FIG. 7(a) corresponds to FIG. 1(a) for the wave energy converter 1a, and FIG. 7(b) and FIG. 7(c) correspond to FIG. 5(b). That is, the solid curves shown in FIG. 7(b) and FIG. 7(c) represent the shape of the water surface when the waves generated above the wave energy converter 1c installed on the seabed 17 are assumed to be sine waves, and the dashed straight lines crossing the curves represent the position of the sea surface (mean water level) when no waves are generated. In addition, the downward arrows in Fig. 7(b) and the upward arrows in Fig. 7(c) correspond to the flow rates of water passing through the inlets 2e, 2g, 2h, and 2k and the outlets 3f, 3i, and 3j, respectively. That is, longer arrows indicate a higher flow rate than shorter arrows. Furthermore, in Fig. 7(b) and Fig. 7(c), the positions of the inlets 2e to 2k, 2m and the outlets 3e to 3k, 3m are indicated by dashed lines, respectively.

[0054] As shown in Fig. 7(a), the wave energy converter 1c is characterized in that the first pressure vessel 2 and the second pressure vessel 3 are arranged parallel to each other, instead of being arranged in a straight line in the wave energy converter 1a, and further includes legs 18 supporting the first pressure vessel 2 and the second pressure vessel 3, and the connecting pipe 4 has flexibility, for example, like a pipe having a bellows structure. Note that the end 2a of the first pressure vessel 2 and the end 3a of the second pressure vessel 3 are also connected via the connecting pipe 4, but since a partition 4e is provided inside the connecting pipe 4, the water inside the first pressure vessel 2 does not move from the end 2a side to the end 3a side of the second pressure vessel 3. In the wave energy converter 1c, as in the case of the wave energy converter 1a described with reference to FIG. 5(b), among the inlets 2e to 2k and 2m, the piezoelectric head on the surface of the first pressure vessel 2 is h 0In the case of FIG. 7(b), the water flows into the first pressure vessel 2 from the part where the piezoelectric head on the surface of the second pressure vessel 3 is larger than h. In the case of FIG. 7(b), the inlets 2e, 2g, 2h, and 2k located directly below the point where the sea level indicated by the solid curve is higher than the average sea level indicated by the dashed line correspond to these inlets. Also, among the outlets 3e to 3k and 3m, the outlets 3e to 3m located directly below the point where the piezoelectric head on the surface of the second pressure vessel 3 is larger than h 0 Water flows out of the second pressure vessel 3 from the portion smaller than the diameter of the second pressure vessel 3. In the case of Fig. 7(c), this corresponds to outlets 3f, 3i, and 3j located directly below the point where the sea level shown by the solid line is lower than the average sea level shown by the dashed line. That is, in the wave energy converter 1c in the state shown in Fig. 7(b) and Fig. 7(c), seawater flows into the first pressure vessel 2 from the inlets 2e, 2g, 2h, and 2k, and then moves into the second pressure vessel 3 through the connecting pipe 4 as shown by the arrow H, and then flows out of the second pressure vessel 3 from the outlets 3f, 3i, and 3j. In this case, the water level of the sea surface changes continuously due to the movement of the waves, so that the inlets through which seawater flows into the first pressure vessel 2 and the outlets through which seawater flows out of the second pressure vessel 3 are switched in order without interruption. As a result, a water flow in a fixed direction that rotates the rotor of the underwater generator 11 is always generated inside the connecting pipe 4 as shown by the arrow H in Fig. 7(a). Therefore, the effect based on such an action is exerted in the wave energy converter 1c as in the wave energy converters 1a and 1b.

[0055] In the wave energy converter 1c, the horizontal state of the first pressure vessel 2 and the second pressure vessel 3 can be easily ensured by adjusting the length of the legs 18, and therefore the wave energy converter 1c can easily change the arrangement (positional relationship between the first pressure vessel 2 and the second pressure vessel 3) to a certain degree so as to reduce the influence of the unevenness of the seabed 17, since the first pressure vessel 2 and the second pressure vessel 3 are connected by a flexible connecting pipe 4. Thus, in the wave energy converter 1c, there are even fewer restrictions on the installation location compared to the wave energy converters 1a and 1b, and therefore the effect of reducing the cost required for installation is further exhibited.

[0056] The wave energy converter of the present invention is not limited to the structures shown in Examples 1 to 3. For example, in the wave energy converter 1a described as Example 1 and the wave energy converter 1b described as Example 2, the connecting pipe 4 is a cylindrical body provided with flanges 4a, 4b at both ends, but it may be a flexible pipe such as a pipe with a bellows structure as in the wave energy converter 1c. The wave energy converter 1c may have a structure including a pedestal having a large support area instead of the legs 18 as a support part for supporting the first pressure vessel 2 and the second pressure vessel. In this case, the horizontal state of the first pressure vessel 2 and the second pressure vessel 3 can be easily ensured by adjusting the height of the pedestal, so that the wave energy converter 1c can be easily installed. The wave energy converters 1a and 1b may also have a structure including a support part consisting of the legs 18 or the pedestal part for supporting the first pressure vessel 2 and the second pressure vessel 3. In this case, the action and effect based on the fact that the connecting pipe 4 has flexibility and is provided with a support part can be exerted in the wave energy converters 1a and 1b in the same manner as in the case of the wave energy converter 1c. Furthermore, in the wave energy converters 1a to 1c, the underwater generator 11 may be installed inside the first pressure vessel 2 or the second pressure vessel 3 without providing the connecting pipe 4. In that case, however, it is necessary to install it inside a cylinder (parts indicated by two straight broken lines inside the first pressure vessel 2 and the second pressure vessel 3 in Fig. 1(a), Fig. 1(b), Fig. 5(b) and Fig. 6(a)) that can pass the same amount of water as the water passing through the connecting pipe 4. Even with such a structure, the action and effect of the wave energy converters 1a to 1c described in the first to third embodiments are similarly exhibited. However, when the underwater generator 11 is installed inside the first pressure vessel 2 or the second pressure vessel 3, it is necessary to pull the first pressure vessel 2 or the second pressure vessel 3 from the seabed to the ground when repairing or replacing the underwater generator 11. In contrast, when an underwater generator 11 is installed inside the connecting pipe 4, it is only necessary to pull up the connecting pipe 4 while the underwater generator 11 remains installed inside, which has the advantage that maintenance work on the underwater generator 11 is significantly easier and maintenance costs are reduced. [Industrial Applicability]

[0057] INDUSTRIAL APPLICABILITY The wave energy conversion device according to the present invention is applicable to cases where power is generated by utilizing the force of waves that naturally occur in the sea. [Explanation of symbols]

[0058] Reference Signs List 1a to 1c...wave energy conversion device 2...first pressure-resistant vessel 2a, 2b...end 2c...upper surface 2d...lower surface 2e to 2k, 2m...inlet 2p...hollow portion 2q...ceiling surface 3...second pressure-resistant vessel 3a, 3b...end 3c...upper surface 3d...lower surface 3e to 3k, 3m...outlet 3p...hollow portion 3q...ceiling surface 4...connecting pipe 4a, 4b...flange 4c, 4d...opening 4e...partition 5...first check valve 6...second check valve 7...base 7a...flange 7b...screw hole 8...rubber plate 8a...notch 8b...screw insertion hole 9...holding plate 9a...opening 9b...screw insertion hole 10...holding plate 10a...small hole 10b...screw insertion hole 11... Underwater generator 12a to 12c... Casing 13... Generator body 14... Runner vane 14a... Reinforcement 14b... Blade 15... Guide vane 15a... Blade 16... Rib 17... Seabed 18... Leg

Claims

1. A first pressure-resistant vessel and a second pressure-resistant vessel each formed of a long hollow member; A first check valve is installed at each of a plurality of inlets provided along a longitudinal direction on an upper surface or a side surface of the first pressure-resistant vessel; A second check valve is installed at each of a plurality of outlets provided along the longitudinal direction on the upper surface or side surface of the second pressure-resistant vessel; an underwater generator installed inside the first pressure-resistant vessel or the second pressure-resistant vessel; The first pressure-resistant vessel and the second pressure-resistant vessel are connected to each other so that water in a hollow portion can move therethrough, each of the first check valve and the second check valve comprises a cylindrical base, a pressing member having a plurality of water passages and installed at one open end of the base, and a rubber plate installed at the one open end of the base so as to be sandwiched between the base and the pressing member; the first check valve is configured so that the one open end of the base is placed at the inlet with the pressing member and the rubber plate sandwiched therebetween, and allows only water to flow into the first pressure-resistant vessel; A wave energy conversion device characterized in that the second check valve has the other open end of the base installed at the outlet and allows only water to flow out from within the second pressure vessel.

2. A wave energy conversion device as described in claim 1, characterized in that the first pressure-resistant vessel and the second pressure-resistant vessel are connected by a connecting pipe, and the underwater generator is installed inside the connecting pipe instead of inside the first pressure-resistant vessel or the second pressure-resistant vessel.

3. 3. A wave energy converter as claimed in claim 2, characterized in that the connecting pipe is flexible.

4. 4. A wave energy converter as claimed in any one of claims 1 to 3, characterized in that the first pressure vessel and the second pressure vessel are arranged parallel to each other.

5. A wave energy conversion device as described in claim 2 or claim 3, characterized in that the first pressure-resistant vessel and the second pressure-resistant vessel are arranged parallel to each other, and the opposing sides of the first pressure-resistant vessel and the second pressure-resistant vessel are connected to each other by the connecting pipe.

6. 6. A wave energy conversion device according to claim 1, further comprising a support portion for supporting the first pressure vessel and the second pressure vessel.

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