JP7736600B2 - Wave energy recovery device and ship - Google Patents

Description

The present invention relates to a wave energy recovery device and a ship, and in particular to a wave energy recovery device capable of generating electricity through the rocking of the hull, and a ship equipped with such a wave energy recovery device.

In recent years, there has been a demand for green innovation in the field of shipping, given environmental issues such as the depletion of fossil fuels and global warming. In particular, for ocean-going ships, which take a long time to complete a voyage, there is a demand for technology that can generate energy in some way during the voyage. When considering ships at sea, wave energy, which rocks the huge hull, is considered to be a promising energy source.

Anti-rolling tanks, such as those described in Patent Document 1, are known as anti-rolling devices for reducing the rolling of a ship's hull while it is sailing or stopped.

The anti-rolling tank comprises a pair of wing tanks spaced apart in the ship's width direction on the port and starboard sides of the upper part of the hull at its widest point, and a duct connecting the wings. The wing tanks and ducts contain liquid, which moves in the ship's width direction between the pair of wing tanks via the duct, thereby reducing the rolling of the hull.

JP 2015-163490 A

The anti-rolling tanks mentioned above are currently only used as roll reduction devices, and do not utilize wave energy as an energy source.

The present invention was devised in light of these problems, and aims to provide a wave energy recovery device and a ship that can generate electricity using wave energy.

According to the present invention, there is provided a wave energy recovery device comprising a pair of side tanks configured to extend vertically, a bottom tank connecting the bottoms of the side tanks, a pair of floats arranged inside each of the side tanks so as to float on liquid contained in the side tanks and the bottom tank, a rope connecting the pair of floats via the outside of the side tanks, a reel arranged in the middle of the rope and around which the rope is wound, and a generator connected to the reel and capable of generating electricity through the reciprocating motion of the rope , wherein the reel is caused to reciprocate by the oscillation of the pair of floats, and the generator generates electricity by rotating the reel through this reciprocating motion.

The wave energy recovery device may be equipped with a guide means for guiding the cable to the generator.

The wave energy recovery device may include a duct connecting the upper parts of the pair of side tanks or an opening formed in the upper parts of the pair of side tanks.

The wave energy recovery device may be equipped with a guide member that guides the swing direction of the float.

The weight of the float may be set to be greater than the buoyancy when completely submerged.

The side tank and the bottom tank may be designed so that their natural periods are based on the peak value of the frequency characteristic curve of the power generation potential expected in use.

The present invention also provides a ship equipped with a wave energy recovery device having any of the above-described configurations.

The pair of side tanks may be arranged along the longitudinal or transverse direction of the hull.

The wave energy recovery device may be installed at a position away from the center of gravity of the ship in the longitudinal, vertical or transverse direction.

The wave energy recovery device and ship according to the present invention described above can convert the rocking of the float into reciprocating linear motion of the rope, which can then be converted into electricity by a generator, recovering the wave energy that rocks the float and generating electricity.

1 is an overall configuration diagram showing a ship according to a first embodiment of the present invention. 1A and 1B are plan views showing examples of the arrangement of a wave energy recovery device, in which FIG. 1A shows a first embodiment and FIG. 1B shows a modified example. 1A and 1B are partially enlarged views showing modified examples of a wave energy recovery device, where FIG. 1A shows a first modified example and FIG. 1B shows a second modified example. 1A and 1B are diagrams showing an example of a tank shape design method, in which (A) shows a hull motion function, (B) shows a frequency spectrum, (C) shows a first example of a frequency characteristic curve of a power generation potential, and (D) shows a second example of a frequency characteristic curve of a power generation potential.

Embodiments of the present invention will be described below using Figures 1 to 4(D). Here, Figure 1 is an overall configuration diagram showing a ship according to a first embodiment of the present invention. Figure 2 is a plan view showing an example of the arrangement of a wave energy recovery device, with (A) showing the first embodiment and (B) showing a modified example.

As shown in Figures 1 and 2(A), a vessel 1 according to a first embodiment of the present invention comprises a hull 2 constituting a floating body, a propeller 3 for propelling the hull 2, an accommodation area 4 arranged on the upper deck 21 of the hull 2, and a wave energy recovery device 5 arranged on the upper deck 21. Note that the configuration of the vessel 1 shown in Figures 1 to 2(B) has been exaggerated.

The ship 1 is, for example, a bulk carrier, and a hatch cover 22 is arranged on the upper deck 21. Note that the ship 1 may also be a cargo ship other than a bulk carrier, such as a tanker, a container ship, or a ferry. The ship 1 is, for example, a large ship, but is not limited to this.

The wave energy recovery device 5 includes, for example, a pair of side tanks 51a, 51b configured to extend vertically, a bottom tank 51c connecting the bottoms of the side tanks 51a, 51b, a pair of floats 52a, 52b arranged inside each of the side tanks 51a, 51b so as to float on the liquid contained in the side tanks 51a, 51b and the bottom tank 51c, a rope 53 connecting the pair of floats 52a, 52b via the outside of the side tanks 51a, 51b, a reel 54 arranged in the middle of the rope 53 and around which the rope 53 is wound, and a generator 55 connected to the reel 54.

Tank 51, which is made up of side tanks 51a, 51b and bottom tank 51c, has an angular, roughly U-shaped shape and contains seawater or other liquid. When tank 51 is placed on a horizontal surface, side tanks 51a, 51b are configured to extend vertically, and bottom tank 51c is configured to extend horizontally.

Liquid is supplied to the top of the side tanks 51a, 51b to form an upper space that allows the liquid to move up and down. A duct 56 is arranged above the side tanks 51a, 51b, connecting the upper spaces of the side tanks 51a, 51b. The duct 56 ensures the flow of air in the upper space between the side tanks 51a, 51b. Note that instead of the duct 56, an air vent valve may be arranged above each of the side tanks 51a, 51b.

Floats 52a and 52b have, for example, a vertically elongated shape, with weights attached to the bottom to adjust buoyancy and stabilize the floating posture. This configuration makes it possible to adjust the buoyancy, floating posture, and draft cross-sectional area of floats 52a and 52b.

The weight W of floats 52a, 52b is set to be greater than the buoyancy Δ when completely submerged. Therefore, floats 52a, 52b have the relationship W > Δ = ρgV, where ρ is the density of the liquid in tank 51 and V is the volume of the liquid. With this configuration, tension can always be applied to rope 53, even when floats 52a, 52b move up and down, preventing rope 53 from slackening.

Furthermore, while the gravity of floats 52a and 52b is greater than their buoyancy at standard draft, by providing reserve buoyancy above the water surface, even if the rope 53 were to break, the buoyancy and gravity of floats 52a and 52b can be balanced in the liquid, preventing damage to tank 51.

The tank 51 sways together with the hull 2, causing the liquid levels in the side tanks 51a and 51b to move up and down relative to each other. Therefore, the floats 52a and 52b also move up and down relative to each other in response to the up and down movement of the liquid level.

A cable 53, such as a wire rope, is connected to the top of the floats 52a and 52b. The cable 53 is inserted through openings formed in the top surfaces of the side tanks 51a and 51b. The cable 53 may be guided to the reel 54 by guide means 57a and 57b arranged on the top of the side tanks 51a and 51b. The guide means 57a and 57b are, for example, pulleys. For ease of explanation, the support members that support the guide means 57a and 57b are not shown in the illustration.

Reel 54 has a winding shaft for rope 53. Both ends of rope 53 are connected to floats 52a and 52b, and the middle section of rope 53 is wound around reel 54 by at least one turn. Therefore, the relative up and down movement of floats 52a and 52b causes rope 53 to be alternately pulled horizontally, causing it to move back and forth. This back and forth movement of rope 53 causes reel 54 to rotate. For ease of explanation, the support member that supports reel 54 has been omitted from the illustration.

The generator 55 is a device that converts the rotational motion of the winding shaft of the reel 54 into electricity. The generator 55 has a rotating shaft that is rotated by the winding shaft of the reel 54. A power transmission mechanism such as a belt drive mechanism or gear mechanism is arranged between the winding shaft and the rotating shaft. The power transmission mechanism may also include an amplifier or a ratchet mechanism that controls the direction of rotation in one direction.

In the above-described embodiment, the reciprocating linear motion of the rope 53 is converted into rotational motion of the reel 54 to generate electricity, but the power generation method is not limited to this configuration. For example, the generator 55 may be a linear generator that converts the reciprocating linear motion of a permanent magnet arranged in the rope 53 into electric power.

As shown in Figures 1 and 2(A), the tank 51 according to the first embodiment has side tanks 51a and 51b arranged along the length of the ship. Furthermore, in consideration of the balance of the hull 2, in this embodiment, the wave energy recovery devices 5 are arranged in two locations, on the port and starboard sides. Furthermore, as shown in Figure 2(B), the tank 51 may have side tanks 51a and 51b arranged along the width of the ship.

The hull 2 generally experiences rotational moments of roll (rolling) around the axis of rotation in the ship's length direction, pitch (pitching) around the axis of rotation in the ship's width direction, and yaw (swaying) around the axis of rotation in the ship's height direction. In the first embodiment shown in Figure 2(A), the pitch (pitching) that occurs in the hull 2 is primarily utilized, while in the modified example shown in Figure 2(B), the roll (swaying) and yaw (swaying) that occur in the hull 2 are primarily utilized.

The wave energy recovery device 5 described above is configured to generate electricity by converting the up and down movement of the floats 52a, 52a into the reciprocating linear movement of the rope 53, so it can utilize all of the motions that occur in the hull 2, including roll (rolling), pitch (pitching), and yaw (yaw).

The orientation of the tanks 51 is determined based on conditions such as the shape of the hull 2, the size of the tanks 51, the type of ship 1, and the expected sea conditions during the ship 1's voyage. Note that, since pitch (pitching) generally has a larger amplitude than roll (rolling) or yaw (yaw), it is preferable to arrange the side tanks 51a, 51b along the ship's length, as in the first embodiment shown in Figure 2(A).

The above-mentioned wave energy recovery devices 5 may be installed in multiple locations on the ship as needed, or may be distributed across different parts such as the upper deck 2, inside the hull 2, and in the accommodation area 4. Wave energy recovery devices 5 with tanks 51 arranged longitudinally and wave energy recovery devices 5 with tanks 51 arranged transversely may also be mixed.

Here, Figure 3 is a partially enlarged view showing modified examples of the wave energy recovery device, with (A) showing the first modified example and (B) showing the second modified example. For ease of explanation, Figures 3(A) and 3(B) only show the configuration on the side tank 51a side of Figure 1.

The modified example shown in Figures 3(A) and 3(B) has a guide member 58 placed inside the side tank 51a to guide the swing direction of the float 52a. By placing such a guide member 58, it is possible to suppress the swinging of the floats 52a and 52b due to the six-degree-of-freedom movement of the hull 2.

The guide member 58 has, for example, a cylindrical or other tubular shape. For example, the upper end of the guide member 58 is supported by a support member 59a connected to the inner surface of the ceiling of the side tank 51a, and the lower end of the guide member 58 is supported by a support member 59a connected to the inner surface of the side of the side tank 51a. For example, multiple support members 59a, 59b are arranged radially around the periphery of the guide member 58. The shape and arrangement of the support members can be designed as desired.

The first modified example shown in Figure 3(A) is one in which a guide member 58 is placed on the tank 51 of the first embodiment shown in Figure 1. The second modified example shown in Figure 3(B) is one in which an opening 51d that communicates with the guide member 58 is formed in the ceiling of the side tank 51a. With this second modified example, the duct 56 can be omitted.

Here, Figure 4 shows an example of a tank shape design method, where (A) shows the hull motion response function, (B) shows the frequency spectrum, (C) shows a first example of a frequency characteristic curve for power generation potential, and (D) shows a second example of a frequency characteristic curve for power generation potential.

In the graph of the ship motion response function shown in Figure 4(A), the horizontal axis represents the encounter wave period (sec) and the vertical axis represents the response value/(wave height/2). In the graph of the frequency spectrum shown in Figure 4(B), the horizontal axis represents the encounter wave period (sec) and the vertical axis represents the wave spectrum (ω). Note that the graphs shown in Figures 4(A) and 4(B) are merely examples.

The frequency characteristic curve of the power generation potential shown in Figure 4(C) is obtained by multiplying the square root of the frequency spectrum of the sea state (wave height and wave period) assumed in the design by the pitch response function for the target ship's sailing speed and average encounter angle with waves. The first example of a frequency characteristic curve of the power generation potential shown in Figure 4(C) is a frequency characteristic curve created from the ship motion response function shown in Figure 4(A) and a sample of the frequency spectrum shown in Figure 4(B).

As shown in Figure 4(C), when the peak value Pc of the frequency characteristic curve of the power generation potential is clear, the dimensions of the tank 51 (side tanks 51a, 51b and bottom tank 51c) are determined so that the period corresponding to the angular frequency at which the peak value Pc is reached becomes the natural period of the tank 51. In other words, the natural period of the tank 51 (side tanks 51a, 51b and bottom tank 51c) is designed based on the peak value Pc of the frequency characteristic curve of the power generation potential expected in the operating state.

The second example of a frequency characteristic curve for power generation potential shown in Figure 4(D) was created using a different sample from the hull motion response function shown in Figure 4(A) and the frequency spectrum shown in Figure 4(B).

As shown in Figure 4(D), if the frequency characteristic curve of the power generation potential does not have a clear peak or has multiple peaks that indicate values close to the peak, the natural period may be adjusted as close to the shortest period as possible (to the left of the figure) to obtain more power. For example, the dimensions of tank 51 (side tanks 51a, 51b and bottom tank 51c) are determined so that the period corresponding to the angular frequency at which peak value Pd occurs is the natural period of tank 51.

The vibration system, which is composed of floats 52a, 52b, rope 53, reel 54, generator 55, etc., may be designed to actively utilize the entrainment phenomenon by making the natural period of the vibration system approximately the same as the natural period of the liquid in tank 51. Also, the vibration system may be designed to simply follow the liquid surface so that the natural period of the vibration system is not entrained with the natural period of the liquid in tank 51.

The wave energy recovery device 5 described above has the characteristic that the greater the inertial force acting on the liquid in the tank 51, the greater the energy absorption effect that can be achieved. As shown in Figure 1, the center of gravity of the hull 2 is defined as G, the horizontal distance between the center of the tank 51 and the center of gravity G is defined as L, the vertical distance from the bottom of the tank 51 to the bottom of the hull 2 is defined as H, the liquid level (vertical distance from the bottom of the tank 51 to the liquid level) is defined as Ht, the height of the tank 51 (vertical distance from the bottom of the tank 51 to the top end of the tank 51) is defined as Dt, and the height of the center of gravity G (vertical distance from the bottom of the hull 2 to the center of gravity G) is defined as Kg.

It is therefore preferable to install the tank 51 in a position as far away as possible from the position of the center of gravity G. Specifically, the tank 51 is installed so that the horizontal distance L or vertical distance H is as large as possible. It is also preferable to install the tank 51 in a position as far away as possible in the ship's width direction from the position of the center of gravity G.

However, when recovering wave energy by utilizing the pitch (pitching) of the hull 2, as in the first embodiment shown in Figure 1, a greater effect can be obtained by installing the tank above the center of gravity G than below it, even if the distance from the center of gravity G is the same. Therefore, H may be set to be greater than or equal to Kg.

Furthermore, in order to utilize the up and down movement of floats 52a and 52b arranged inside tank 51, it is preferable to set the liquid level height Ht near the center of tank height Dt. In other words, it is set so that Ht ≒ Dt / 2.

The wave energy recovery device 5 and ship 1 according to the present embodiment described above can convert the rocking of the floats 52a, 52b into reciprocating linear motion of the rope 53, which can then be converted into electricity by the generator 55, thereby recovering the wave energy that rocks the floats 52a, 52b and generating electricity.

In addition, by using the electricity recovered by the wave energy recovery device 5 on board the ship, it is possible to reduce the number of diesel generators installed on the hull 2, and also to reduce greenhouse gases and other emissions generated when burning heavy oil.

The present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present invention.

1 Ship 2 Hull 3 Propulsion unit 4 Accommodation space 5 Wave energy recovery device 21 Upper deck 22 Hatch cover 51 Tanks 51a, 51b Side tank 51c Bottom tank 51d Openings 52a, 52b Float 53 Rope 54 Reel 55 Generator 56 Ducts 57a, 57b Guide means 58 Guide members 59a, 59b Support member

Claims (9)

a pair of side tanks configured to extend in a vertical direction;
a bottom tank connecting the bottoms of the side tanks;
a pair of floats disposed inside the side tanks so as to float on the liquid contained in the side tanks and the bottom tank;
a cable that connects the pair of floats via the outside of the side tank;
a reel disposed at an intermediate portion of the cord body and around which the cord body is wound;
a generator connected to the reel and capable of generating electricity by the reciprocating motion of the rope body,
The reel is reciprocated by the swinging of the pair of floats , and the reel is rotated by this reciprocating motion, thereby generating electricity with the generator.
A wave energy recovery device characterized by:
A wave energy recovery device as described in claim 1, comprising a guide means for guiding the cable to the generator. A wave energy recovery device as described in claim 1, comprising a duct connecting the upper portions of the pair of side tanks or an opening formed in the upper portion of the pair of side tanks. A wave energy recovery device as described in claim 1, equipped with a guide member that guides the swinging direction of the float. A wave energy recovery device as described in claim 1, wherein the weight of the float is set to be greater than the buoyancy when completely submerged. The wave energy recovery device described in claim 1, wherein the natural periods of the side tank and the bottom tank are designed based on the peak value of the frequency characteristic curve of the power generation potential expected in use. A ship equipped with a wave energy recovery device according to any one of claims 1 to 6. The vessel described in claim 7, wherein the pair of side tanks are arranged along the longitudinal or transverse direction of the hull. The ship according to claim 7 , wherein the wave energy recovery device is installed at a position away from the center of gravity of the ship in the length direction, height direction, or width direction.