JP7714228B2 - Water current power generation device - Google Patents

Description

The present invention relates to a water current power generation device.

It is said that ocean currents contain several hundred TWh of energy per year around the world. Because ocean currents are more stable than the fluctuations of solar and wind power, power generation using ocean currents has attracted attention as a stable power generation method. Furthermore, because ocean current power generation does not emit carbon dioxide (CO2), it has also attracted attention as a natural energy source with an extremely low environmental impact.
BACKGROUND ART Conventionally, there has been a technology that uses the water current of the sea or a river to rotate a rotor such as a propeller, thereby converting the kinetic energy of the water current into electrical energy to generate electricity.

Patent Document 1 describes a technology for generating electricity using tidal currents. This technology involves installing a support rod at a fixed position underwater, mounting screw blades on the support rod that rotate in response to the tidal current, and using the torque of the screw blades, which are rotated by the tidal current, to drive a generator inside a station installed above the sea surface to generate electricity. The cylindrical rod supporting the screw blades is rotatably attached to the support rod so that the screw blades are oriented to face the tidal current.

Patent Document 2 describes a technology in which an underwater rotor is placed on a vertical member fixed to the seabed, and the rotational energy generated by ocean currents rotating the underwater rotor is transmitted to a generator on the sea. The underwater rotor and the support are connected by a universal joint mechanism, so the rotor can be rotated freely in any direction, up and down, left and right.

Japanese Patent Application Laid-Open No. 2002-257023 JP 2009-121241 A

However, in the invention of Patent Document 1, the transmission and generator are located at a floating station on the sea, and require rotational force transmission materials such as gears to transmit the rotational energy received by the screw blades from the tidal current to the transmission and generator on the sea. Using rotational force transmission materials to transmit rotation can complicate the mechanism and may result in energy loss.

Furthermore, while the invention of Patent Document 2 can freely change the orientation of the underwater rotor in response to changes in the direction of ocean currents, because it is connected by a small contact point called a universal joint mechanism, it is difficult to ensure sufficient strength and there is a risk of the joint breaking.

The present invention was made in light of these circumstances, and aims to generate stable, efficient electricity from water flow, even in environments where the water flow direction fluctuates.

The invention described in claim 1 is a water current power generation device comprising: a hollow support; a rotatable hollow rotating support connected to the support; a rotor that rotates due to water flow; a rotor support member having one end fixed to the rotating support member and supporting the rotor; and a shaft that is fixed to the rotor and rotates integrally with the rotor, wherein the shaft passes through the internal space of the rotor support member and is connected to a generator; the rotor support member has a cylindrical body extending in the direction of the rotation axis of the rotor, and the rotor is rotatably supported by a convex portion protruding radially outward from the rotor support member facing a concave portion on the inside of the rotor .

The invention described in claim 2 is a water current power generation device described in claim 1 , characterized in that the transmission cable connected to the generator is laid in the internal space of the rotating body support member or the support pillar.

The invention described in claim 3 is the water current power generation device according to claim 1 , characterized in that the range of angles through which the rotating support can rotate is less than 180 degrees.

This invention enables stable and efficient power generation from water flow, even in environments where the direction of the water flow fluctuates.

1 is a perspective view showing a water current power generation device according to a first embodiment of the present invention. 1 is a cross-sectional view of a water current power generation device according to a first embodiment of the present invention. FIG. 10 is a cross-sectional view showing a water current power generation device according to a second embodiment. FIG. 10 is a cross-sectional view showing a water current power generation device according to a third embodiment. FIG. 10 is a diagram showing a water current power generation device according to a fourth embodiment. FIG. 10 is a diagram showing an example in which a plurality of water current power generation devices according to the first or third embodiment are arranged. FIG. 10 is a diagram showing an example in which a plurality of water current power generation devices according to the second or fourth embodiment are arranged. FIG. 10 is a diagram showing an example in which a plurality of water current power generation devices according to the third embodiment are arranged. FIG. 10 is a diagram showing another example in which a plurality of water current power generation devices according to the third embodiment are arranged. FIG. 10 is a diagram showing an example in which the water current power generation devices according to the third and fourth embodiments are combined.

The power generation device according to the present invention will be described with reference to the drawings. Note that the present invention is not limited to the following embodiments.

(First embodiment)
Fig. 1 is a perspective view showing a water current power generation device according to a first embodiment of the present invention. As shown in Fig. 1, the water current power generation device 1 of this embodiment comprises a support pole 3 extending vertically from a floating station 2 on the sea, a rotating support pole 4, a support pole 5, an anchor 6, a mooring rope 7, a rotor 8, and a rotor support member 9.

Station 2 is a facility that floats on the sea surface due to buoyancy. The support pole 5 is connected to an anchor 6 installed on the seabed via a mooring line 7, so the water current power generation device 1 can remain in a fixed position without being swept away by ocean currents. The rotor 8 generates electricity by rotating under the force of the ocean current. The rotating pole 4 rotates so that the rotor 8 and rotor support member 9 are located downstream of the rotating pole 4 in the direction of the ocean current.

In this specification, "water current" refers to the flow of water or seawater, and includes not only the direction of laminar flow, in which the flow lines are aligned in layers, but also turbulent flow, in which the flow lines are disturbed. "Direction of water current" refers to the main direction of the entire flow, whether it is laminar or turbulent. Unless otherwise specified, "upward" refers to the direction from the bottom of the water to the surface, and "downward" refers to the direction from the surface of the water to the bottom. Also, unless otherwise specified, "forward" refers to the upstream direction of the water current, and "backward" refers to the downstream direction of the water current.

In this specification, a "rotating body" refers to an object or device that receives the force of a water current and converts the water current energy into rotational energy. Therefore, it is desirable for the rotating body to be equipped with blades that can receive the water current and convert it into rotation. The blades may be propellers, or may have a spiral shape that is oblique to the axial direction of the rotating body.

The rotor 8 is a structure that can convert the energy of the water flow into rotational energy for the rotor 8. For example, in the example shown in Figure 1, the rotor 8 is installed downstream of the rotating support 4, and multiple blades 10 attached to the rotor 8 receive the water flow and rotate the rotor 8. It is desirable that the blades 10 have a shape that allows the rotor to easily rotate when receiving the water flow, so they may be formed in a spiral shape that surrounds the body of the rotor.

The length of the rotor 8 in the direction of the rotation axis may be made greater than its radial diameter (at the center of the body), allowing it to rotate with the water current while extending downstream, making it less susceptible to vertical oscillation. In the first embodiment, the rotor 8 has a radial diameter of approximately 10 m and a length in the direction of the rotation axis of approximately 20 m. The rotor 8 may be made of resins such as fiber-reinforced plastic (FRP) or carbon-fiber-reinforced plastic (CFRP), or metals. If the rotor is made of a titanium alloy, it will not rust even in water and can be used semi-permanently.

Figure 2 is a cross-sectional view of a water current power generation device according to the first embodiment. A rotating support 4 is rotatably disposed between support 3 and support 5. The connecting portion between support 3 and rotating support 4 is arranged so that the protruding portion of support 3 faces the recessed portion of rotating support 4, and they are in contact with each other via bearings 16a. The connecting portion between rotating support 4 and support 5 has a similar configuration to the connecting portion with support 3. Rotating support 4 freely rotates around its central axis so that the rotor 8 can be positioned downstream of the ocean current or facing upstream as the direction of the ocean current changes. Rotating support 4 may be configured to rotate 360° freely. However, because the power transmission cable would be twisted if the ocean current continued to rotate clockwise or counterclockwise, the rotation angle may be limited to a predetermined angle less than 180° around the main direction of the ocean current. The mechanism for limiting the angle of the rotating support may be configured with a stopper or other device that prevents further rotation after a certain angle.

The rotating support 4 requires a hollow space to accommodate the power transmission cable 21 or generator 20. Support 3 or support 5 is preferably hollow to ensure sufficient space for the power transmission cable to extend. When leading the power transmission cable to the seabed, at least the lower support 5 is made hollow and the power transmission cable is passed downward. On the other hand, when leading the power transmission cable to an offshore relay point, at least the upper support 3 should be hollow.

The rotating body 8 and rotating body support member 9 are arranged so that the recessed portion 12 inside the rotating body engages with the protruding portion 13 of the rotating body support member 9, and are in contact with bearings 14a and 14b. The rotating body support member 9 is hollow. A shaft 11 fixed inside the rotating body 8 is housed in the hollow space of the rotating body support member 9 and is connected to a generator 20 located in the internal space of the rotating support column 4. As a result, the rotational energy of the rotating body 8 is transmitted to the generator 20 via the shaft 11, generating electricity. "A shaft that transmits the rotation of the rotating body to the generator" includes not only a shaft directly connected to the generator, but also a shaft that transmits rotation to the generator via a transmission or the like.

The rotor support member 9 is a cylindrical member extending parallel to the rotation axis of the shaft 11, with the shaft 11 passing through the interior of the rotor support member 9. One end of the rotor support member 9 is fixed to the rotary support column 4, and the other end is disposed so as to be housed inside the rotor 8. A convex portion 13 that protrudes radially outward from the outer wall surface of the rotor support member 9 housed inside the rotor 8 is formed on the outer periphery of the cylinder. The convex portion 13 is disposed so as to face a groove-shaped concave portion 12 formed on the inner wall surface of the rotor 8. As a result, even when the water current is strong, the rotor 8 is supported by the convex portion 13 of the rotor support member 9 fixed to the rotary support column 4, and the rotor 8 will not come off the water current power generation device and be swept downstream by the water current, and will be able to maintain its rotational motion.
Furthermore, although not shown, the rotor support member 9 may have an extendable structure while being fixed to the rotating support column 4. If the structure is extendable, the distance of the rotor 8 from the rotating support column 4 can be adjusted, so that the rotor 8 can be positioned at an optimal position where the resistance of the rotating support column 4 to the water flow is minimized.

In this specification, "facing" refers to a state in which opposing components fit together, but the opposing components do not necessarily have to be in contact with each other; it also includes a state in which the opposing components are separated from each other but restrict specific movements of the opposing components. For example, "facing" includes a structure in which opposing components support each other via oil, bearings, or a combination thereof, even if the convex and concave portions do not come into direct contact.

A number of bearings 14a, 14b may be arranged on the outer periphery of the cylinder of the support member on the front and rear sides of the convex portion 13. The rear bearing 14b must be strong enough to withstand the force of the water current trying to wash away the rotor 8. The presence of the bearings 14a, 14b reduces resistance to the rotational motion of the rotor 8, allowing it to rotate at higher speeds. Furthermore, the space formed by the concave portion 12 and convex portion 13 of the rotor 8 can be filled with oil, allowing the rotor 8 to rotate smoothly and stably. When filling the concave portion 12 with oil, known technology can be used to create a sealed structure to prevent oil leakage.

There are no particular restrictions on the size or material of the recessed portion 12 and the protruding portion 13, as long as they are strong enough to withstand the force of the water currents that the rotor 8 receives and maintain stable rotation. Furthermore, if the depth of the recessed portion 12 is greater than the height of the protruding portion 13, the space between the recessed portion 12 and the protruding portion 13 can be filled with oil or bearings, allowing for smooth rotation.

The bearing 14a on the front side of the convex portion 13 and the bearing 14b on the rear side of the convex portion 13 may or may not be the same size. The rear bearing 14b needs to be strong enough to withstand the force of the water flow trying to sweep away the rotor 8 while also maintaining rotation, so it may be a bearing with a larger diameter than the front bearing 14a. Making the rear bearing 14b larger than the front bearing 14a allows for stronger support against the force of the water flow pushing the rotor backward.
Furthermore, the number of bearings 14b on the rear side of the convex portion 13 may be greater than the number of bearings 14a on the front side of the convex portion 13 arranged around the rotor 8. By arranging more bearings 14b on the rear side of the convex portion 13, the number of contact points between the convex portion 13 and the plurality of bearings 14b increases, which makes it possible to strengthen support against the force of the water flow pushing the rotor backward and also exerts the effect of suppressing the swinging of the rotor 8.

A waterproofing mechanism may also be provided to prevent water from entering the cavity inside the rotor 8. The waterproofing mechanism may be a known waterproofing technique, such as an O-ring 15 placed in the gap between the rotor 8 and the rotor support member 9, as shown in Figure 2, to maintain rotation while preventing water from entering the rotor.

In the example shown in Figure 2, a recess 12 is provided on the rotor 8 and a protrusion 13 is provided on the rotor support member 9, but the recess-protrusion relationship may be reversed. That is, a recess may be provided on the rotor support member 9, and a protrusion protruding radially inward from the inner wall surface of the rotor may face the recess on the rotor support member 9.

The rotor in this embodiment is a downwind type rotor that rotates downstream of the rotating support strut 4. Because the resistance of the rotating support strut 4 reduces the flow speed of ocean currents and causes turbulence, it is desirable to position the rotor 8 a certain distance away from the rotating support strut 4. It is desirable to position the rotor at a distance at least equal to or greater than the diameter of the rotating support strut.

As explained above, the water current power generation device according to the first embodiment can efficiently generate power even in environments where the direction of ocean currents fluctuates, while suppressing the oscillation of the rotor 8. Furthermore, in the water current power generation device according to the first embodiment, the shaft 11, which rotates integrally with the rotor 8, is directly connected to the generator inside the rotating support 4, so there is less rotational energy loss due to a transmission mechanism using gears or the like compared to when the generator 20 is installed on the sea.

Second Embodiment
Figure 3 is a cross-sectional view showing a water current power generation device according to a second embodiment. The second embodiment differs from the first embodiment in that when the rotor 8 rotates due to the force of the ocean current to generate power, the rotor 8 is located upstream of the rotating support column 4, i.e., it is an upwind type. In the first embodiment, because the rotor 8 is located downstream of the rotating support column 4, it was necessary to make the rotor support member 9 long and streamlined to take into account the effect of the resistance of the water flow caused by the rotating support column 4, which reduces power generation efficiency. In the second embodiment, because the rotor 8 is located upstream of the rotating support column 4, it is not necessary to lengthen the rotor support member 9 located downstream of the rotor 8.
It is also desirable to provide a waterproof mechanism between the rotor 8 and the rotor support member 9. In Fig. 3, an O-ring 15 is disposed, but other known waterproof mechanisms such as a bellows may also be used.

The rotating support 4 rotates so that the rotor 8 faces upstream due to the force of the ocean current. In other words, the rotating support 4 rotates so that the rotor 8 faces the ocean current. If, instead of the rotating support 4, a rotor support member 9 were fixed in a specific direction to a non-rotating support, the rotor 8 would receive the water current from an angle or sideways, causing the rotor 8 to rotate inefficiently and increasing vibrations, resulting in reduced power generation efficiency. In this embodiment, the rotation of the rotating support 4 allows the rotor 8 to face in the most efficient direction, enabling efficient power generation.

(Third embodiment)
4 is a cross-sectional view of a water current power generation device according to a third embodiment. The third embodiment differs from the first embodiment in that the generator 20 is housed in the internal space of the rotor support member 9 and that a transmission 30 is interposed between the generator 20 and the shaft 11. However, the other configurations are the same as those of the first embodiment.
By accommodating the generator 20 and the transmission 30 in the internal space of the rotor support member 9, the length of the shaft 11 can be shortened, and the internal space of the rotary support column 4 can be made small.

(Fourth embodiment)
5 is a cross-sectional view showing a water current power generation device according to a fourth embodiment. The fourth embodiment differs from the second embodiment in that the generator 20 is housed in the internal space of the rotor support member 9 and that a transmission 30 is interposed between the generator 20 and the shaft 11. However, the other configurations are the same as those of the second embodiment.
By accommodating the generator 20 and the transmission 30 in the internal space of the rotor support member 9, the length of the shaft 11 can be shortened, and the internal space of the rotary support column 4 can be made small.

(Embodiment in which multiple rotating bodies are arranged)
The water current power generation device according to the first embodiment and the water current power generation device according to the third embodiment are devices that generate power with the rotor 8 located downstream of the rotary support column 4. A plurality of water current power generation devices according to the first embodiment or the third embodiment can be arranged.
For example, in the example shown in Figure 6, rotors are arranged in series at three different vertical depths. Ocean currents may flow in different directions depending on the depth. In such cases, in this example, each rotating support 4 can rotate so that the rotors are positioned in the optimal direction at each of the different depths, thereby improving overall power generation efficiency compared to a system in which the rotors are fixed in a specific direction.

The water current power generation device according to the second embodiment and the water current power generation device according to the fourth embodiment are devices that generate power with the rotor 8 located upstream of the rotary support column 4. A plurality of water current power generation devices according to the second embodiment or the fourth embodiment can be arranged.
For example, in the example shown in Figure 7, rotors are arranged in series at three different vertical depths. Ocean currents may flow in different directions depending on the depth. In such a case, in this example, each rotating support 4 can rotate so that the rotors are positioned in the optimal direction at each of the different depths, thereby improving overall power generation efficiency compared to a system in which the rotors are fixed in a specific direction.

In the water current power generation device according to the third embodiment, the generator 20 is housed inside the rotor support member 9. Here, the rotor support member is not limited to a member consisting solely of members extending linearly from the rotor toward the rotating support column 4, as shown in Figure 4. For example, Figure 8 shows an example in which multiple water current power generation devices according to the third embodiment are arranged. In this example, the rotor support member 9 is composed of members 9a, 9b, and 9c connected together. Although not shown, each of members 9a, 9b, and 9c has a hollow space inside, so the power transmission cable connected to the generator can reach the inside of the support column via the hollow space in the rotor support member 9.

Figure 9 shows another example of an arrangement of multiple water current power generation devices according to the third embodiment. In this example, three rotors are arranged on a horizontal plane at the same depth. A generator is located inside each rotor support member. If generators were placed inside the rotating support column 4, either three generators would be placed in the internal space of the rotating support column 4, or a complex transmission mechanism would be required to transmit the rotation of each rotor to the rotating support column 4. In this example, the generators are located inside each rotor support member, and power transmission cables can run from each generator through the inside of each rotor support member to the inside of the rotating support column 4, ensuring that there is no shortage of space inside the column.

Figure 10 shows an example of a combination of the water current power generation devices according to the third and fourth embodiments. If the rotors are placed at the same depth, the rear rotor will be affected by changes in the water flow caused by the front rotor, so it is desirable to keep the distance between the front and rear rotors as long as possible.

In the embodiments described herein, a power generation device that uses underwater ocean currents has been described, but the present invention is not limited to ocean currents and includes power generation devices in places with flowing water, such as rivers and lakes.

1...Water current power generation device, 2...Station, 3...Support, 4...Rotating support, 5...Support, 6...Anchor, 7...Mooring line, 8...Rotor, 9...Rotor support member, 10...Blade, 11...Shaft, 12...Concave, 13...Convex, 14a, 14b...Bearing, 15...O-ring, 16a, 16b...Bearing, 20...Generator, 21...Transmission cable, 30...Transmission

Claims (3)

A hollow support pillar,
a hollow rotating support rod connected to the support rod and rotatable;
A rotating body that rotates due to the water flow;
a rotor support member having one end fixed to the rotary support column and supporting the rotor;
a shaft fixed to the rotating body and rotating integrally with the rotating body,
The shaft passes through the internal space of the rotor support member and is connected to a generator,
the rotor support member has a cylindrical body extending in the direction of the rotation axis of the rotor,
A convex portion protruding radially outward from the rotor support member faces a concave portion on the inner side of the rotor, thereby rotatably supporting the rotor.
A water current power generation device characterized by: 2. The water current power generation device according to claim 1 , wherein a power transmission cable connected to the generator is laid in an internal space of the rotor support member or the support column. 2. The water current power generation device according to claim 1 , wherein the range of rotation angles of the rotating support is less than 180 degrees.