JP2002257022A - Wave energy transducer utilizing pressure difference - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve relatively high operation efficiency not affected much by the irregular variation of the frequency and amplitude of waves. SOLUTION: A slender cylinder is completely sunk under water in the vertical direction just under the average water level of the ocean, etc. The cylinder has the length determined by the surface wave with a prescribed wavelength. The top of the cylinder is affected by relatively large pressure variation according to passing waves, while the bottom of the cylinder is hardly affected by the passing waves and receives nearly constant pressure. Relative movement is generated between the cylinder and adjacent water by utilizing the pressure difference at both ends of the cylinder in the longitudinal direction, and a piston of the energy transducer is driven by utilizing the relative movement. The cylinder is hollow so that water can pass through it and may be mounted at a fixed position, or may be movable under water relative to the fixed transducer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the conversion of energy from naturally occurring mechanical energy sources, and more particularly to the conversion of mechanical energy present in ocean surface waves into useful energy, particularly electrical energy.

[0002]

BACKGROUND OF THE INVENTION Many conventional systems for capturing surface wave energy use floats to oscillate vertically in response to passing waves. The float is fixedly coupled to an energy converter that is driven according to the vertical movement of the float. In one system described in U.S. Pat. Nos. 4,773,221 and 4,277,690, the subject matter of which is incorporated herein by reference, an open-ended hollow tube is provided. Hanging fixedly below the float, the tube is completely submerged and vertically oriented.

[0003] In response to the movement of the float, the tube oscillates vertically in the water, and if there is nothing in the tube, the tube is free to move relative to the water column in the open-ended tube. In one embodiment,
A movable piston is positioned within the tube to prevent relative movement between the water column and the tube. When the tube and the float vibrate in the water, the piston moves relative to the tube as the water mass in the tube tries to obstruct the corresponding movement of the piston. However, the actual movement of the piston does occur, and if the entire system is oscillating at the natural resonance frequency, the piston can oscillate at a relatively large amplitude. The moving piston can convert the piston movement into useful energy, for example, by driving an energy converter fixedly mounted in the float.

While these float-operated tube systems work effectively, efficient operation requires that the natural resonance frequency of the system be approximately equal to the frequency of the waves driving the system. In particular, if means are provided for adjusting the resonant frequency of the system in response to the changing frequency of the surface wave, this can generally be achieved at a specific location and at a specific time, but at any time a large number of irregularities However, there is a problem that many of the existing wave energy cannot be effectively transmitted to the vibration system. Also, means for adjusting the resonance frequency of the device generally requires changing the amount of water in the device. This water volume is so large that it does not change easily.

[0005]

It is a feature of the present invention to achieve relatively high operating efficiencies with little sensitivity to irregular changes in wave frequency and amplitude.

[0006]

According to a first embodiment of the present invention, an open-ended hollow tube is disposed at a fixed position submerged perpendicularly to an average water level. That is, the tube is not "floating" (movable) with respect to the passing wave. As described below, the length of the tube and the depth of the top of the tube from the average water level are selected according to the water depth, along with the frequency and amplitude of the surface waves that are expected to be the most common. When the expected wave is present, the maximum operation efficiency is obtained, but the decrease in the operation efficiency due to the change in the wave state is relatively small.

The change in pressure (due to the passing wave) at the open top end of the tube compared to the pressure being relatively fixed at the open bottom end (unaffected by the passing wave) of the tube,
Water flows vertically in the tube, which is used to drive the energy converter, preferably by a movable piston in the tube.

In the second embodiment of the present invention, a hollow tube having a closed top end and an open bottom end is perpendicular to the average water level and submerged, but is disposed so as to be relatively movable. I have. In a preferred embodiment, the tube is fixed so as to be submerged fixedly below the surface of the water and to move periodically in a direction perpendicular to a float disposed in the tube. The dimensions of the tube and its rest position relative to the water surface are as in the tube of the first embodiment, but in the second embodiment the piston movable in the tube of the first embodiment is Includes closed upper end. During operation, due to the change in pressure applied to the top of the tube,
The tube vibrates perpendicularly to the fixed float, and the vibration is used to drive an energy converter fixed within the float and coupled to the movable tube. In a modification of the second embodiment, the converter is not mounted in the float but is fixed to the sea floor. The movable tube need not be hollow, but is fixed to the transducer.

In all embodiments, the movement of the tube relative to the adjacent water occurs in response to pressure changes caused by passing waves, rather than by displacement of the float at the surface of the water due to wave guidance.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An apparatus according to a first embodiment of the present invention is shown in FIG. A water body having a wind-generated surface wave, for example, an open-ended tube 10 fixed below and vertically oriented (as described herein) below the average water level of the ocean is shown schematically. . FIG. 1 also shows the parameters important for the practice of the present invention: wave height, wavelength, water depth, depth of the top of the tube from the water surface, tube length and tube diameter. The optimum depth at the lower end of the tube is determined by the wavelength (λ) of the longest wave that can be used efficiently. The principle of operation is that the change in water energy level, which can be expressed as a pressure change due to the passage of a wave peak and valley, is greatest near the surface, and these pressure changes decrease exponentially with depth from the water surface That's what it means. Thus, the top of a long tube experiences a relatively large pressure change, while the bottom of the tube experiences a substantially constant pressure, which is equal to the pressure due to the weight of the water above it at the average water level.

The energy levels at various water depths from the wavefront can be calculated with equations 1 and 2. These equations are for deep ocean waves and shallower oceans (λ / 2
(Depth less than) is somewhat modified. The water energy level due to a certain wave size is a function of wavelength and water depth. 1 / of the wavelength of the longest wave that can use the bottom of the tube optimally
Extending deeper than 2 has little practical value since the energy level has already been greatly reduced from the value near the surface.

Ed = Es exp (−2πd / λ) (1) where Ed is energy due to a wave on the water surface, and Ed is
Is the energy of the wave at the depth d, and λ is the wavelength of the considered wave. Wavelength of the wave of the deep sea is calculated as ^{λ = gT 2 / 2π (2} ). Where g is the gravitational constant, 9.8 meters / second / second, and T is the period of the wave in seconds.
As an example using Equation 2, for a wave with a period of 7 seconds, the wavelength is λ7 = 76.43 meters. As a second example, for a wave with a period of 5 seconds, the wavelength is λ5 = 38.99 meters.

For a wave having a period of 7 seconds and a wavelength of 76.43 meters, and a wave having a period of 5 seconds and a wavelength of 38.99 meters, energy at various depths is calculated using equation 1 at the water surface. It can be calculated as a percentage of energy. This is shown in Table 1.

[0014]

[Table 1]

Table 1 shows that a wave having a period of 7 seconds exists,
When the top end of is at a depth of 0.5 meters from the water surface and its bottom end is at a depth of 38.21 meters from the water surface,
The top shows a 91.7% (96-4.3) greater pressure change than the bottom. Due to these conditions,
Water flows down the inside of the tube as the wave peaks rise above the top, and water rises inside the tube when the wave trough comes to the top of the tube. This pressurized water stream provides an opportunity to extract mechanical power from the wave energy. Increasing the length of the tube from 38.21 meters to 76.43 meters only increases the pressure differential by 4.1% (4.3-0.2).

Further examination of Table 1 shows that when a wave with a period of 5 seconds is present, a tube whose bottom is at a depth of 38.21 meters from the water surface has a pressure change at the bottom where a wave with a period of 7 seconds is present. It can be seen that it is even smaller than 0.2%. Therefore, it is possible to efficiently collect wave energy from a wave having a short wavelength and a short cycle. As the wave period becomes longer, the energy at the bottom of the tube, that is, the pressure change, gradually increases. Therefore, the energy recovery efficiency gradually decreases. However, the effective operating range is much wider than in the prior art devices described above, which are tuned to a specific wave period to obtain resonance and effective operation. With those devices,
If the wave period changes even a few seconds, the efficiency will be greatly reduced.

Table 1 also shows that as the wave period decreases, the importance of the upper part of the tube near the water surface increases. For example, when the wave depth at the top of a pipe is 0.5 meters above the water surface in a 7-second wave, the energy at the top of the pipe decreases to 96% of the maximum value. To 92.3% of the value.

A regular wave is a wave having a constant period. A sine wave is an example of a regular wave. In the case of a regular wave having a constant period, the wave period changes and the above-described negative influence
Even with t), the resonant wave energy capture device could be tuned to a specific wave period. In practice, waves are irregular and irregular, and simultaneously contain waves of different periods. As an example of this, there is a case where a swell having a period of 10 seconds exists together with a wind wave having a period of 5 seconds. The device of the present invention has the ability to efficiently capture energy from irregular waves as well as regular waves. This is because the device is not optimized for a particular cycle, but is driven according to the instantaneous water volume above or below the average water level (but suffers the "cancellation effect" described below).

The theoretical amount of energy that can be captured at a location having certain water depth and wave characteristics can be determined as follows. Bernoulli equation for fluid unstable non-rotating _{flow, δφ 1 / δt + P 1} / ρ + gy 1 + V 1 2/2 = δφ 2 / δ
t + is a _{P 2 / ρ + gy 2 +} V 2 2/2. Here, (1) is one point in the fluid, and (2)
Is another point in the fluid, δφ / δt is the derivative of the velocity potential at a point, expressed in square meters / square second (m ² / s ² ), and gy is the gravitational constant The value obtained by multiplying the depth at a certain point by m ² / s ² , and P / ρ is the value obtained by dividing the pressure at a certain point by the fluid density, and is expressed by m ² / s ² . represented (in order to achieve these dimensions, it is necessary to remember that can represent mass as a value obtained by dividing the force by the acceleration), V ^2/2
Is the square of the velocity of the fluid at that point, m ² / s ²
Expressed in units.

For example, if point 1 is near the water surface, such as at the top of the tube, and point 2 is deeper, at the bottom of the tube,
The Bernoulli equation can be the basis for analyzing the various forms of energy obtained at each point over time.

Working Principle-Energy Capture: The simple and long tube described above provides a situation where two different pressure levels appear simultaneously at each end of the tube. Two preferred methods of capturing energy from the available energy in the tube are described below.

1. Piston 12 of FIG. 2 arranged in a tube
Is forcibly driven up and down by water in the pipe moving up and down due to the fluctuating pressure difference above and below the piston. By attaching a device to the piston that resists movement of the piston, this forced movement is converted to mechanical power. One example is the rod of a hydraulic cylinder. The movement of the cylinder rod causes the pressurized fluid (hydraulic oil) to flow into the hydraulic motor, thereby rotating the motor. Mechanical power generated by the hydraulic motor is converted to electric power by a generator attached to the motor. In FIG. 2, the water-driven piston 12 and its shaft are shown to move up and down while being guided by the piston shaft support and shaft bearing 16. Preferably, the piston does not contact the side of the tube to reduce the mechanical drag on the system. 3-6 between piston rim and tube
With a millimeter gap, some water will leak through the piston. This means a loss of power, but only a small percentage of the area for pistons greater than one meter in diameter. (Hydraulic cylinder 20
A hydraulic cylinder rod 18 is mounted on top of the piston shaft 12. A hydraulic cylinder support 22 fixedly attaches the cylinder 20 to the tube 10. Hydraulic hose 24 feeds and sends hydraulic oil back and forth to the liquid tight chamber containing the hydraulic motor and generator. Because the cylinder performance is the same in both stroke directions, a double-ended cylinder (with rods extending from both ends) is preferred. The piston is configured to have sufficient buoyancy to cause the piston-piston shaft-hydraulic cylinder rod assembly to float neutrally and thus to move up and down equally with the same force. A preferred arrangement of the components is shown in FIG. 2A. In this arrangement, the piston 12 is mounted on the hydraulic cylinder itself and slides up and down. Both ends of the hydraulic cylinder rod 18 are fixedly attached to the pipe 10 by a hydraulic cylinder rod support 22. A fluid tight chamber 26 forms part of the piston assembly and houses a hydraulic motor and a generator. This chamber has sufficient buoyancy to allow the entire piston assembly to float neutrally.

FIG. 2 also shows a structure for mooring the power conversion system. This will be described later.

FIG. 3 shows a structure in which the area of the piston 12 is larger than the area of the upper and lower ends of the tube 10. This is to show that the area of the piston can be larger or smaller than the area of the end of the tube. In some situations, the structure of FIG. 3 will produce greater force and shorter strokes than if the piston and tube end had the same area. This is because the length and depth of the tube determine the pressure differential across the piston, and the tube end area determines the volume of the water flow. Therefore, when the same pressure is applied to a large piston area, a large force is generated, but a large amount of water is required to move the large piston. FIG. 3 shows that the piston dimensions can be changed for the desired piston force and stroke. However, every time the moving water is turned, there is an energy loss, even when the piston area is different from the tube end area. For this reason, the shape with the highest energy efficiency is
It is when the piston and the pipe end have the same area.

As a second power take-out method (not shown), there is a method in which a rod that moves vertically with the piston is attached to the piston. This piston rod is not mounted on a hydraulic cylinder, but on a secure drive belt (with teeth for meshing engagement of the belt and sprocket) which is hung on two vertically arranged sprockets. When the wave energy drives the piston up and down, it drives one side of the belt up and down, causing the sprocket to rotate. One of the shafts of the driven sprocket is coupled to the generator to generate electricity.

As a third power extraction method (not shown), there is a method in which a linear power generator (such as a linear electric motor) is directly driven by moving a piston. Due to the subsea environment, hydraulic methods are preferred.

2. In the system shown in FIG. 4, a turbine 40 is located in the tube 10 and is rotationally driven by water flow in the tube moving up and down due to the fluctuating pressure difference between the top and bottom of the tube. This rotation produces mechanical power, for example, by coupling the shaft of generator 42 to turbine shaft 44. The tube preferably has a large diameter end and a small diameter turbine section, as shown, so that the speed of water flow through the turbine can be increased.

In general, the moving piston method (1) is preferred because the system of the present invention is more easily designed to provide a strong stroke of limited length than to provide high velocity water flow. Each method is described in further detail below.

1. Moving piston method: When a piston as shown at 12 in FIGS. 2, 2A and 3 moves against resistance, it generates a force (Newton). The piston moves a fixed distance for a predetermined time (meters / second). The value of this force multiplied by the speed is Newton-
Meters / second (Nm / s), which is directly converted to power wattage. 1 Nm / s is equal to 1 Watt. Power (Watts) = Power (Newton) x Speed (meters / second) (3)

A long stroke with a small force at a given time generates the same amount of force as a short stroke with a large force at the same time, and vice versa. When using the piston method in practice, there is a limit to the length of the piston stroke that can be tolerated. This is because actual devices, such as hydraulic cylinders, have a certain amount of stroke and, beyond their physical limits, break the cylinder. Also, waves at certain locations are typically within a known magnitude range throughout the year.
For this reason, it is economically impractical to provide a device that allows a stroke greater than that normally present. Prevention of destruction by waves larger than normal waves, such as storm waves (not shown), is provided by pressure relief doors located in the tube 10 above and below the range of motion of the piston 12. If the wave creates a pressure difference across the piston that is greater than a predetermined value (and the resulting piston force), the door is pushed open. This allows water to bypass the piston, reducing its force and preventing destruction of the device.

The piston system is typically provided for a range of physical strokes, such as one meter, but can be longer or shorter. However, the force can be increased or decreased simply by increasing or decreasing the unit and its piston. This is an important factor in the construction of a practical system and is based on the fact that the fluid pressure is not determined by the size of the area affected by it. For example, suppose, as described above, that a wave is to be expected that gives an average pressure difference of 2,000 Pascal (Pa) between the top and bottom of the tube. Pascal is
There is a pressure of 1 Newton per square meter. Also, assume that the cycle of the wave is 5 seconds, that is, the wave moves from a peak to a valley in 2.5 seconds. Piston stroke is 1
If it is limited to meters and it is traveling a full stroke, its average speed is 1 / 2.5 = 0.4 m / s. 1000 watts from the system, ie 100
If 0 Nm / s is desired, the average force is (1000 Nm /
s) / (0.4 m / s) = 2,500 N. The pressure difference is 2,000 Pa, ie 2,000 N
/ M ² , the piston area is (2,500 N)
^{/ (2,000N / m 2) =} 1.25m must be ^2. This corresponds to a piston diameter (D) of 1.26 meters.

The water mass in the tube and piston area moves with the piston. It must be accelerated in one direction, decelerated and stopped, accelerated in the other direction, decelerated and stopped, and so on. Therefore, a part of the force generated by the pressure difference applied to the piston must be used for accelerating the water mass. Since the force is a value obtained by multiplying the mass by the acceleration, that is, F (water) = m (water) · a, this can be calculated. Some of this force can recover from water deceleration. However, the need to accelerate and decelerate large bodies of water makes the optimal length of the tube 10 less than half the wavelength. This is because longer tubes capture a greater pressure difference than shorter tubes but contain more water. The optimal length of the tube 10 can be calculated for individual wavelengths, wave heights and water depths using the Bernoulli equation as described above.

In summary, the features of the moving piston method are as follows. 1. A tube of sufficient length to produce a large fluctuating pressure difference between the top and bottom ends when subjected to a range of wavelengths of waves. 2. A piston in a tube where fluctuating pressure from the top of the tube is obtained on the top surface and relatively constant pressure from the bottom of the tube is obtained on the bottom surface. 3.1. And 2. Therefore, the piston is driven up and down with a certain force and speed. 4.3. Means such as hydraulic cylinders and motors for converting reciprocating mechanical power into rotary mechanical power. 5.4. A generator that converts rotating mechanical power into electric power. 6. The piston diameter may be larger or smaller than the tube diameter and will produce either a slow motion with a relatively large force or a fast motion with a relatively small force. 7. The dimensions of the system's tubes and piston components affect the amount of water mass enclosed within the system,
Affects the amount of piston and water acceleration that can be obtained from certain wave environments.

The additional requirements are further described below: The system can use a mooring anchored to the sea floor or a mooring that forms a float unit for balancing the piston force with a suitably sized buoyant portion. 9. The system can use mooring that combines fixed buoyancy mooring with additional buoyancy to compensate for tidal changes by moving the top of the tube up and down as the tide ebbs.

Various mooring structures are described below.

2. Description of the turbine method: The operating principle of a unit that uses a water turbine instead of a moving piston to extract power is very similar. The important difference is that high speed water flow is required. As shown in Equation 3, force and speed contribute equally to the power output. Power (Watts) = Power (Newton) x Speed (meters / second) (3)

The moving piston method is, for practical reasons,
The stroke and therefore the speed must be limited. For this reason, the force is emphasized by providing a large piston area. When using a turbine to extract power from a flowing fluid, high speeds are desirable to overcome initial stiction and to ensure that the turbine begins to rotate for efficient operation. The power that can be captured from the cross-sectional area of the fluid flow is given by: power (Watts) = 0.5 × A × ρ × V ³ (4) Where A is the cross-sectional area of the flow in m ² , and ρ is the fluid density (1000 kg / m
³ ), V is the velocity in meters / second. A high average speed is desirable to optimize power output. The optimal thrust or force applied to the turbine in the fluid flow is given by: Thrust (Newton) = (3/8) x A x ρ x V ² (5) Given a velocity profile determined for a given tube shape and waveform, the expected power output can be calculated from equation (4). Also, the amount of buoyancy needed to maintain the tube in a fixed position in proportion to the thrust can be calculated from equation (5).

Next, the mooring of the above embodiment will be described.

In the example shown in FIG. 2, a mooring attachment to the seabed is shown. The mooring attachment acts as mechanical data to resist the upward and downward forces of the piston and holds the tube in place.
The mooring attachment must be strong enough to withstand the downward forces generated by the unit, and must have a weight to resist the upward forces generated by the unit. It must be firmly mounted on the sea floor to resist the forces generated by the storm waves.

There may be places where the sea is too deep to actually attach to the sea floor. FIG. 5 shows a structure in which the system of the invention can be moored at virtually any water depth due to the variable length of the mooring chain 17. Tube 10
It is held in a vertical position by a buoyancy tank 50 attached to its outer periphery. These buoyancy tanks have sufficient buoyancy to allow the unit to float to the surface of the water unless the unit is held by a mooring chain or cable. The tank has sufficient buoyancy to support the sum of the weight of the unit and at least the maximum downward force exerted by the piston on the tube. This prevents the power generation tube from lowering during normal operation.
The mooring chain must be at least strong enough to resist the sum of the net upward force of the buoyancy tank and the maximum upward force generated by the piston against the tube. The anchor must also have a weight at least as great as the sum of the net upward force of the buoyancy tank and the maximum upward force generated by the piston on the tube to prevent the anchor from floating.

In the case of the fixed depth mooring structure shown in FIGS. 2 and 5, changes in water depth due to tides will affect power acquisition performance. At normal tidal range, for example, one meter, the effect is small. A preferred mooring plan is to moor the unit at a planned depth from the water surface at the midpoint of a tidal change. In that case, there will be times when it is too deep from the surface (high tide) than planned, and when it is too close to the surface (low tide). From Table 1, it can be seen that the energy level at the top of the tube, 1 meter below the average plane of the 7 second period wave, is 4% lower than at 0.5 meters below the average plane. For this reason, a unit moored 1 meter below the surface of the water at mid-tide when the tidal range is 1 meter is within ± 0.5 meters from the planned depth during the day. Will. Units moored so shallow that the wave troughs expose the top of the unit have little or no loss of power output. Thus, fixed moored units as described above occur at approximately average planning levels in a normal tidal environment. In areas with large tidal differences, the units are preferably mounted low in the sea so that they are not overexposed during the wave troughs. As would be expected from Table 1, this will reduce the average power that the unit can capture. To meet certain power goals,
Units that are slightly larger than those where the tide changes are small are needed. At locations that are within extreme water depths and tidal ranges, the simplicity of fixed mooring generally outweighs power loss.

The second mooring method, shown in FIG. 6, combines a fixed bottom mount with a floating tube top. The fixed bottom installation provides the above simplicity and the float compensates for tides. In this case, the upper part 15 of the tube
Can expand and contract, and can be extended upward by the buoyancy of the small float 62 when the average water level rises at high tide. At low tide, the float 62 descends with the water level, compressing and shortening the elastic upper tube portion 15. The float maintains the top of the tube at a relatively constant depth from sea level, eg, one meter. The apparent change in the height of the water above the pipe is approximately the same whether it rises and falls above the top of the fixed open pipe where the water is fixed, or above and below the pipe extension. In this configuration, the fixed mooring buoyancy tank 60 counters the large forces generated by the pistons operating in the pressure drive mode, and the additional buoyancy tank 62 only moves the top of the tube up and down.

Next, a second embodiment of the present invention shown in FIGS. 7 to 9 will be described.

FIGS. 7-9 show a hollow tube 110 having a closed top end 112 and an open bottom end 114. FIG. As described earlier in the first embodiment, the tube 110 is submerged and provided vertically, but unlike the tube 10 of the first embodiment, which is preferably fixed at a predetermined position, the second The tube 110 of the embodiment is vertically movable with respect to the fixed support. Such a support may be a rigid structure attached to the seabed, but especially in deep seas, a float 116 fixedly moored to the seabed 118 with anchors 120 and chains or cables 128. Is preferred.

[0045] Most conveniently, tube 110 is float 11
Because the tube surrounds 6 and the tube is vertically elongated, the float 116 is also elongated.

The float 116 corresponds to a fixed structure fixedly attached to the sea floor except that the float 116 has a large buoyancy and the float can be displaced horizontally to some extent according to the horizontal movement of water. Such horizontal displacement of the float generally occurs at a low speed, and substantially the function of the float is
The purpose is to give the position of the fixed tube relative to the seabed.
In situations where the water level changes significantly, known means of adjusting the distance between the float and the sea floor to maintain a constant distance between the float and the water surface are used. However, as described in the description of the first embodiment, since the power generation is not significantly affected by a moderate water level change, the float is generally arranged so as to obtain the optimum performance at the average water level, and thereafter, the float is disposed. The position is not changed according to the change.

The tube 110 is secured to the float by a well-known type of hydraulic pump 122 having a rigid casing 124, and a piston rod 126 (for pumping fluid in the hydraulic pump) extends through the casing 124. It extends out from both ends. Here, the pump casing 124 is fixed to the movable tube 110 by a spoke-shaped bracket 121 (so as not to hinder the movement of water in the tube 110). The upper end of the pump casing 124 is fixed to the closed upper end of the pipe 110, but one end 126b of the piston rod 126 passes through the pipe end. (Optionally, a navigation aid 127 is attached to rod end 126b and projects upwardly from the sea surface. The other end 126a of piston rod 126 is fixed to float 116. The tube has a neutral buoyancy. And a hollow buoyancy chamber 125. Since the tube 110 has a neutral buoyancy, the tube 110 vibrates vertically according to a pressure change between the upper and lower portions of the tube caused by the passing wave as described above. Vibrates vertically with respect to the fixed float 116, causing relative movement between the pump casing 124 and the pump piston rod 126, thereby generating an alternating water pressure in the pump, and using this to pump fluid to the hose 111 a To the hydraulic motor-generator 111
Can be driven.

Elements that affect the structure of the entire system are the same as those described in the description of the first embodiment. In the first embodiment, the piston in the stationary tube moves according to the passing wave. In the second embodiment, the closed (upper) end 112 of the tube 110 functions as a piston movable with respect to the fixed support.

In operation, tube top 112 is submerged with all passing waves within the wave magnitude at which the device was designed to operate. A pressure relief valve in the form of, for example, a spring-loaded door 130 shown in FIG. 9 is used at the upper end 112 of the tube 110 to eliminate excessive force due to excessive waves.
Here, four doors 130 are shown. If the pressure difference between the water above the tube and the water inside the tube exceeds a predetermined level, two of the doors will open downward to equalize the pressure inside and outside the tube 110. The remaining two doors 130 open upward to relieve internal overpressure due to the wave trough passing above (or below) the top end 112 of the tube being too deep. The spring force pressing the door 130 can be obtained from the weight of the buoyancy chamber applied to the door.

An advantage of the cable-fixed construction shown is that the unit is free to move horizontally by the action of waves. This reduces the horizontal force on the mooring device,
The required mooring equipment mass is reduced. Large horizontal movement
An attempt is made to lower the pipe upper end 112 with respect to the sea surface. This descent tends to reduce the output power of the unit that would be obtained when the upper end 112 is at an optimum depth from the water surface (as described above). However, as described above, the change in the amount of power generation with the increase in the depth of the pipe end from the water surface is somewhat gradual, and the effective power generation continues even when the unit is greatly inclined in the horizontal direction. .

To avoid breakage due to the mechanical connection of the float 116 and the tube 110, relative horizontal movement therebetween is preferably avoided. For such movement to occur, water must move in the tube 110 in the lateral direction of the float 116 in response to the lateral movement of the tube 110. Such movement of water and concomitant relative movement of float 116 with respect to tube 110 is substantially achieved by using longitudinal, radially extending fins 117 shown in FIGS. Is prevented.

By arranging the float 116 in the pipe 110 as described above, a self-contained unit is obtained which can be easily assembled and transported on the shore and easily installed underwater. In such an arrangement, the float 116 functions as a fixed support to which the transducer is fixedly attached, and the transducer is coupled to and driven by the movable tube 110.

In the modified arrangement shown in FIG. 10, a transducer 222 (eg, a hydraulic tube, etc.) is mounted on the seabed (preferably by a mechanical joint, such as a ball and socket joint 232, that allows the transducer 222 to pivot). 7.) A fixedly mounted, movable piston rod 226 of the transducer is fixedly attached to the bottom end of a neutral floating tube 210 identical to the tube 110 shown in FIGS. 7-9 but without the internal float. It is connected to. The tube 210 is provided by an anchor link 228 (also preferably at a pivot joint), which can be an anchor chain or a solid rod, preferably having a high modulus of elasticity, i.e., low strain for applied stress.
It is connected to a piston rod 226.

In the first patent issued to the owner of the present invention (US Pat. No. 4,404,490), the "cancellation effect" when the size of the wave energy recovery machine is a large fraction of the wavelength of the surface wave. That is, the energy looting effect
(the subject matter of this patent is incorporated herein by reference). As used herein, for example, changes in pressure between upper and lower ends of various tube lengths disclosed herein occur in response to passing waves. For example, if the tube diameter is the same as the wavelength of the passing wave, the pressure increase created by the crest overlying the top of the tube will be counteracted by the simultaneous presence of the trough of the passing wave. Therefore, no vertical vibration of the tube occurs. However, waves tend to be very large, and for practical reasons, the diameter of the tube is very small compared to the wavelength, so that the diameter of the tube is quite small,
For example, if it does not exceed 10%, the canceling effect can be ignored.

Such a canceling effect occurs in a direction parallel to the moving direction of the wave. Since there is no cancellation in the direction perpendicular to the wave direction, a tube of very large area with a rectangular cross section can be used if the long axis (more than 10% of the wavelength) can be maintained perpendicular to the wave direction. Can be used.

In the embodiment shown in FIG. 10, the transducer 222 is located below and outside the tube 210 (as in FIG. 7).
There is no need to provide a hollow space in the tube 210 to accommodate the 22 and the float 116, and the tube 210 need not be hollow and need not have an open bottom end. In accordance with the present invention, what is required for tube 220 is a closed top end that has the same external dimensions (so that it can be used in the same wave environment) and that acts as a piston that responds to surface wave pressure changes. It only resembles tube 110 in having. The tube 220, like the tube 110, must have a neutral buoyancy so that it oscillates vertically in response to a change in the pressure between the upper and lower sides generated by the passing wave, but the tube may be hollow, but as desired. It can be as solid as possible.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing various relevant dimensional parameters of a system according to the invention placed underwater.

FIG. 2 is a side cross-sectional view showing one form of the first embodiment of the power conversion system of the present invention disposed in water such as the ocean.

FIG. 2A is a side cross-sectional view illustrating one form of the first embodiment of the power conversion system of the present invention disposed in water, such as the ocean.

FIG. 3 is a side cross-sectional view showing one form of the first embodiment of the power conversion system of the present invention disposed in water such as the ocean.

FIG. 4 is a side cross-sectional view showing one form of the first embodiment of the power conversion system of the present invention disposed in water such as the ocean.

FIG. 5 is a cross-sectional side view showing one form of the first embodiment of the power conversion system of the present invention disposed in water such as the ocean.

FIG. 6 is a side cross-sectional view showing one form of the first embodiment of the power conversion system of the present invention disposed in water such as the ocean.

FIG. 7 is a side view of an energy converter according to a second embodiment of the present invention.

FIG. 8 is an end view of the transducer as viewed in the direction of arrows 8-8 in FIG.

FIG. 9 is a perspective view of the converter shown in FIGS. 7 and 8;

FIG. 10 is a side view of a variation of the embodiment shown in FIGS.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Meredith Bell United States 18950 Pennsylvania, Point Pleasant, Tohiken Hill Road 7690 F-term (reference) 3H074 AA02 AA12 AA20 BB01 BB12 CC02 CC10 CC50

Claims (9)

[Claims] 1. An apparatus for capturing energy from a predetermined surface wave on a body of water that varies from a maximum to a minimum wavelength and has a maximum amplitude above and below an average water level present during passage, said energy being captured relative to said average water level. A vertically mounted elongate cylinder which is substantially submerged and whose top end is structurally spaced from the surface of the water and substantially equal to said maximum amplitude in the absence of surface waves. At a first depth, the bottom end of the cylinder has a second level whose energy level corresponding to the wave of the maximum wavelength is a small percentage of the energy corresponding to the wave of the maximum wavelength at the average level. Arranged at a depth, wherein the cylinder is
An apparatus comprising a barrier that obstructs the flow of water through the cylinder to convert water movement to the cylinder into captured energy. 2. The apparatus of claim 1, wherein said second depth is equal to about 50% of said maximum wavelength wave. 3. The cylinder is hollow and has an open upper end, is fixedly attached to the average water level, and the barrier is slidably disposed within the cylinder to convert energy. The apparatus of claim 1 including a piston connected to the vessel. 4. The apparatus according to claim 1, wherein said cylinder has a closed upper end functioning as said barrier, said cylinder being slidably connected to an energy converter. 5. The apparatus according to claim 4, wherein the energy converter is fixedly attached to a float fixed to the bottom of the water. 6. The apparatus of claim 5, wherein said float and said energy converter are located within said cylinder. 7. The apparatus according to claim 4, wherein the energy converter is fixed to the bottom of the water, and the cylinder is fixedly connected to the energy converter. 8. A method for capturing energy from predetermined surface waves on a body of water that varies from a maximum to a minimum wavelength and has a maximum amplitude above and below an average water level present during passage, wherein the energy is captured within the body of water. Arranging an elongate cylinder in a vertical orientation completely submerged relative to the average water level, the cylinder having a top end structurally away from the water surface at a first depth approximately equal to the maximum amplitude. And the bottom end of the cylinder is located at a second depth where the energy level corresponding to the wave of the maximum wavelength is a small percentage of the energy corresponding to the wave of the maximum wavelength at the average level. Further, in order to convert the movement of water with respect to the cylinder to trapped energy, the flow of water through the cylinder is obstructed in accordance with a difference in water pressure between the upper and lower cylinders caused by the passing wave. Disposing a rotating barrier in the cylinder. 9. The method of claim 8, wherein said second depth is equal to about 50% of said maximum wavelength wave.