FR2475146A1 - Buoyancy supported wave power device - has reaction element with plate or membrane moving under action of wave forces converted into electrical generation - Google Patents

Abstract

The device is buoyantly supportable and comprises a reaction element (10) and a plate or membrane element (12) which can move back and forth to react against the reaction element (10). The movement of the plate or membrane element which is caused by the cyclic application of wave forces is converted into a more readily usable form by, for example, an air or hydraulic transmission and electrical generation driven by the pressure of the air or hydraulic fluid which arises by virtue of the back and forth movement of the plate or membrane elements. In a preferred arrangement, a single spine (35) supports the plate elements (36) which are movable individually and in some applications the individual plate elements are coupled so that, in one case, as certain elements are moving towards the spine, others are being displaced away from the spine, and in other cases the relative displacements of adjacent elements are utilised to provide the pumping of hydraulic fluid or air.

Description

The present invention relates to an energy generating device capable of being used to convert the wave energy of a liquid body, such as a sea or an ocean, into a usable form.

There are many proposals for converting the wave energy of a liquid; the main of these proposals involve a primary component, which is positioned so as to be influenced by the waves, which move it backwards and forwards. This back-and-forth movement is converted into a more usable form, for example into electrical energy, by means of an appropriate transmission.

In a known method, the primary component is adapted to be able to pivot around an axis and has a pallet on the side of the waves which is raised and lowered by it, while downwind there is no displacement. Of course, a plurality of such devices can be mounted in parallel.

However, the development and manufacture of such known devices, even on the scale of a tenth, have raised such difficulties that it is doubtful that these devices can be really usable.

In addition, there are two other kinds of difficulties which are raised by these devices.

First, it is necessary to find an axis which is able to resist satisfactorily at the time of anticipated bending, when such a shaft does not seem available and then, problems arise with regard to the taking of power primary, the accessibility to the bearings and the robustness of the device to withstand survival conditions, for example storm conditions.

The object of the present invention is to remedy these drawbacks and it relates to an apparatus intended to replace these known apparatuses, mentioned above.

To this end, according to the invention, a floating device for generating energy from the movement of the waves of a liquid body comprises a reaction element and a movable element in the form of a plate, functionally connected to the reaction element so as to be able to move back and forth to react against the reaction element, when the plate-shaped element is influenced by the waves of the liquid body, and has means to extract wave energy in another more usable form thanks to the relative movements between the reaction element and the plate-shaped element.

Preferably, the reaction element is a part of an elongated frame and there are a plurality of plate-like elements arranged along at least one side of the frame, when the apparatus is used in parallel at the front of the waves from which the energy must be extracted or at an angle, preferably an acute angle, with said front; or, said elements. in the form of a plate can be arranged side by side on either side of the frame, when the latter is used in a position orthogonal to the front of the waves.

The means for extracting energy from the beat movement of the plate-shaped elements can be of any suitable type such as a hydraulic pump with an appropriate transmission, or said plate-shaped elements can be arranged to act like pneumatic pistons for pumping air which can be sent into conduits or collectors arranged in the frame, the compressed air being used as a means for rotating a turbine which, in turn, drives for example an electric generator.

In order to dampen the movement of the plate-shaped elements, each of these can define with the framework a cavity whose volume decreases and increases when the movable element moves in the direction of and opposite the framework said cavity being capable of containing a liquid acting as a damping means for the beating movements of the mobile element.

When there is a liquid in said cavity, the level thereof increases when each plate-shaped element rocks in the direction of the framework because of the lifting movement exerted by the waves on the movable element; the rise in level naturally means an increase in the column of liquid and therefore an increase in the force tending to bring the movable element in the direction opposite to the beam.

The two respective parts of the frame and of the movable element which face each other and which come into contact and separate when the movable element oscillates are preferably shaped correspondingly, so that in an extreme position of this element mobile, said cavity is reduced to zero or contains only a very thin film of said liquid.

Preferably, the liquid contained in said cavity is the same as that in which the device floats. In such an arrangement, it is preferable that the cavity is provided to allow passage. between the liquid of the liquid body and that contained in the cavity.

According to a preferred embodiment of the present invention, said plate-shaped elements arranged along the frame are capable of following the instantaneous movements of the waves along the latter, so that the plate-shaped elements can move out of phase, and there are coupling means interconnecting said plate-shaped elements so that when the waves touch some of the elements towards the framework, other plate-shaped elements on which the action of the waves is also exerted, out of phase, being far from the frame.

In this arrangement, the plate-shaped elements can be sealed with respect to the framework in order to avoid a liquid current between each plate element and the framework, when the plate element is separated from the framework. alternatively, there may be pumping means for pumping the liquid out of the spaces between the plate elements and the spar.

In another alternative embodiment, plate-shaped elements are defined by a continuous flexible membrane supported from place to place along the framework by supports which can move backwards and forwards with movement of flat elements and which define the element in plate form.

Said coupling means can be for example a tensioned rope, a cable or the like, extending longitudinally to the frame and passing over three groups of pulleys, one group for each plate element, two pulleys of each group being carried by the frame and the third being movable in synchronism with the associated plate element
Alternatively, the plate elements may each be connected to a hydraulic pump, the pumps being connected to a common pressure supply.

Said interconnected means are preferably connected to transmission means for transforming the movement of the plate elements into another form of energy such as rotary movement, fluid pressure or electrical energy. In the case where there is a single frame carrying the plate-shaped elements arranged side by side and facing the incident waves, and, to extract the energy from the waves, by appropriate means and connected to the absorbent elements, the means the most common for extracting energy involves hydraulic pumps, such as piston and cylinder devices, which convert the movements of the element into a pressurized fluid (preferably the same as that of the body of liquid) and this fluid under pressure can obviously be used to drive a mechanical device such as a turbine for the possible production of electrical energy, which is the usual purpose of the device of the type to which the invention relates.

It has been found that it is preferable to control the displacement of each of the absorbent elements so that the inertial forces do not become too large, as could happen in large seas, and of course if the absorbent elements were left free to beat in harmony with the waves, the device could be self-destructive. It is therefore preferable that the movements of each of the absorbent elements be damped or braked as a function of the instantaneous speed of the element. It has also been found that the damping of the elements as a function of said speed also provides maximum efficiency for converting wave energy into hydraulic energy.

Unfortunately, the majority of hydraulic pumping devices are fixed displacement pumps and are designed to operate against constant hydraulic pressure, and without modification could not function op-timally with a plate-shaped element back and forth, the speed of which changes cyclically.

Variable displacement pumps can be used in conjunction with such plate-like elements but are complex, expensive and less efficient than fixed displacement pumps and as they are less robust than fixed displacement pumps, they would have a life of life too short in the application of the invention. In addition, variable displacement pumps include mechanical extractors or valve-controlled gears to allow the displacement to be varied and such gears or such extractors must be controlled by a hydraulic and / or electrical servo system from the proportional speed control which can be difficult to generate.

The present invention makes it possible, as will be explained below, to use fixed displacement pumps, to dampen the movement of the absorbent elements as a function of the speed.

Thus, according to a preferred form of the present invention, each of the plate-shaped elements is connected to damping means, the damping of which varies according to the degree of phase shift relative to the adjacent plate-shaped element.

When the waves are applied cyclically and when the instantaneous force of the waves along the frame changes cyclically, the phase difference between the adjacent plate-like elements is a measure of the instantaneous speed or the relative speed of the the element or elements and pairs of element-shaped plates can be hydraulically coupled by similar hydraulic devices with fixed displacement and with pistons and cylinders, coupled by control valves so that when two plate-shaped elements of the pair are in phase, the piston and cylinder devices are phase shifted so that one unloads its movement in the other and there is no damping. If the adjacent plate-shaped elements are phase shifted by 1800, the damping is maximum and the devices can be arranged to discharge.

When the spar is long, and there are a lot of plate-shaped elements, there are always at least some of the elements which are out of phase, because the instantaneous force of the waves is different along said spar.

Instead of fixed displacement hydraulic pumps, other means of energy conversion can be used.

In a particularly interesting arrangement, when the plate-shaped elements are arranged to function as air pumps, the frame can have two common air collectors, one being a high pressure manifold and the other a manifold at low pressure. Each plate-shaped element is associated with the two collectors respectively by two valves so that when the plate-shaped element rocks in the direction of the framework it pumps air from the cavity between the element in the form of plate and frame to introduce it into the high pressure manifold through a high pressure valve, while the low pressure valve is closed. When the plate-like element moves away from the frame, the The air flows towards the cavity through the low pressure valve, while the high pressure valve is closed and the cycle is repeated with each back and forth movement of the plate-like element.

In a particularly advantageous arrangement of the present invention, "framework is actually the hull of a motor ship, of the tanker type with regard to the dimension, the plate elements being mounted on the sides of the ship.

An advantage of such an arrangement is that the ship can be maneuvered into the best position relative to the front of the waves from which the energy must be extracted. Means may be provided for bringing the plate-shaped elements back to the outward position after it has been moved inward by the waves and such means may for example be springs or the like.

The frame may preferably include ballasts to allow it to float in a predetermined position in the liquid and it is preferable, for its stability, that the frame is relatively massive compared to a plate-shaped element.

The figures of the appended drawing will make it clear how the invention can be implemented.

Figure 1 is a schematic sectional view illustrating an apparatus according to a first embodiment of the invention.

FIG. 2 illustrates the relative positions of the plate-shaped elements as a function of the propagation of a wave.

FIG. 3 shows an example of the conversion of the movement of the plate-shaped element into rotational movement.

Figure 4 shows how the movable plate-like element can be placed in survival conditions.

Figure 5 illustrates the movement of the frame in use.

FIG. 6 illustrates how the ends of the cavity can be reduced to a limited extent.

Figures 7 and 8 show alternative embodiments of sections for the beam and the movable member.

Figure 9 illustrates how the frame can be tensioned using cables.

Figure 10 is a plan view illustrating the principle of another embodiment according to the present invention.

Figure 11 is a sectional view showing two arrangements of plate-like elements.

Figure 12 is a plan view of an apparatus according to another embodiment of the invention.

Figure 13 is a plan view of an apparatus according to another alternative embodiment of the invention.

Figure 14 is a plan view of an apparatus according to a third embodiment of the invention.

Figure 15 is a plan view illustrating a frame portion provided with a plurality of energy absorbing elements.

Figure 16 shows how a pair of energy absorbing devices shown in Figure 15 can be hydraulically coupled according to another alternative embodiment.

Figure 17 shows an apparatus for explaining other embodiments of the invention.

Figures 18, 19 and 20 show respectively the device of Figure 17 in section, the section being taken along the line
II-II of Figure 17 and the three figures respectively showing the device in different positions.

FIGS. 21, 22 and 23 respectively show, in a manner similar to FIG. 18, three embodiments of the invention of the type of FIG. 17.

Figures 24, 25 and 26 are views similar to Figures 21, 22 and 23 but showing different energy conversion modes.

Figure 27 shows how a spar and a plate can be arranged.

Figure 28 shows how a floating vessel can be provided with plate-shaped elements to form an alternative embodiment of the invention.

Figure 29 is an enlarged view illustrating the use of a plate-like member as an air pump.

Figure 30 is a view similar to Figure 29, but illustrating a different embodiment.

The device according to the invention shown in Figure 1 comprises a frame 10 having the shape of a cylindrical reaction element. On this framework 10 are articulated elements 12 in the form of a plate which in the example is in the form of flaps articulated around axes 14.

The frame 10 and the flaps 12 are floating elements, the frame 10 having ballasts 16 to fix its floating position in calm water, the level of this water being indicated by the line WL The internal face 18 of the flap 12 is curve to adapt to the curvature of the frame 10, but, in calm water, the usual position shown in FIG. 1 provides a cavity 20 between the frame 10 and the flap 12.

The cavity 20 normally contains a certain quantity of liquid which is the same as that in which the device according to the invention floats, for example sea water.

To explain the fundamental principle of operation, it is assumed that the cavity 20 between the flap 12 and the framework 10 is partially filled with water in a low-tilt position, the neutral position being such as that shown in FIG. 1, all weight and float moments
being balanced. When the height of the wave increases, the flap 12 rotates anti-clockwise and its movement is counteracted by the elastic action of the level of the water rising in the cavity 20. When the height of the wave decreases, the flap 12 rotates clockwise, and is also counteracted by the elastic action of the decreasing water level in the cavity.

The average water level in the cavity 20 is determined by the movement of the flap 12 relative to the average position of said flap. In conditions where there is no wave, the water level in the cavity will be the average sea level, the angle of the flap being determined by the frame-flap geometry and by the weight / buoyancy distribution. When the wave height increases, the water from the cavity is gradually expelled so that the average level of the water decreases in the cavity. Figure 2 shows a plurality of flap positions related to a sine wave model.

The constant state of the water level in the cavity for particular sea conditions is determined by the balance of expulsion and leakage of water, controlled or not, into and out of the cavity. inertia and elasticity of the flap 12 are a function of the structural geometry and the mass of the flap -and of the ratio of the volumes of air and water in the cavity 20, which can consequently be tuned to the frequency band wave energy.

In a practical example, it is necessary that there be means for adjusting the oscillation movements of the flap 12.

An example is shown in Figure 3.

Referring to FIG. 3, a curved power arm 22 fixed to the flap 12 rotates around the articulation 14 and transmits a mechanical drive to the device 24 on the upper surface of the frame 12. The arm 22 can be provided with 'a rack for driving hydraulic pumps coupled to said rack or a rolling surface for a drive by friction roller. A direct-acting seawater pump is not excluded. Several arms 22, distributed along the flap 12 may be provided, each cooperating with a sliding or sheathed joint at the point of entry into the power device 24.

In the case of very high seas or in storms, the angular movement of the flap may get out of control or may decrease the volume of the cavity towards zero during peaks of climb. When the volume of the cavity decreases, the wave acting on the flap is compensated by the pressure due to the expulsion of water out of the cavity. This non-linear damping of the movement of the flap avoids direct contact of the frame and of the flap 12 during operation.

In the case where the shutter can no longer be controlled, it is advantageous to lock it in position (Figure 4).

If the flap is prevented from moving from its position close to contact, it is practically made integral with the framework with regard to the action of the waves. The forces of these are transmitted to the frame by the sealing contacts and the hydrodynamic pressure of the water between the flap and the frame. The movements of the flap 12 relative to the frame are avoided by locking the arm 22 or the end sections of the flap 12.

Of course, in operation, the frame also tends to roll or rotate. The rotation of the frame, which is due to its buoyancy, can be used as an advantage.

In calm conditions, the flotation-ballast distribution in the frame section is such that the cavity has a minimum volume when it is full of water. During the wave height increase station, the rotation of the flap increases which increases the average volume of the cavity. A larger average cavity volume increases the buoyancy on the side of the frame facing the wave. The force acts in the form of a torque causing the rotation of the frame.

This rotation movement of the frame moves the location of the joint to lift the flap and increase the volume of the capacity, with concomitant increase in the inertia of the flap. This effect is illustrated in FIG. 5.

 It is preferable that the cavity 20 is sufficiently but not completely sealed with respect to the surrounding water, so that the cavity 20 can itself be self-pumping.

Leakage rates of up to 1/10 of the volume of the operational cavity per wave cycle may be tolerated and may even be necessary for efficient operation. The joint at the joint 14 can be obtained by simple equipment with tolerances or by a perfectly tight flexible flap. The joints at the ends raise greater difficulties.

An end seal arrangement is shown in Figure 6. A low tolerance sliding joint between the ends of the flap is obtained by dividing plates 26 carefully mounted between the adjacent ends of the flaps. With such an arrangement, leakage is tolerable provided that the end slots are not more than 10 cm, which would be sufficient to cope with adjustable construction tolerances and load distortions.

The adoption of a shutter as a primary component, compared to the known devices described above, gives many more possibilities to the device according to the invention. A cylindrical frame had already been provided for these prior known devices but had raised many problems. Considerations concerning the bending moments required that the maximum length of the rigid framework should not be more than 250 m for a mobile element of 10 m. The longer frame lengths should have included joints with two degrees of freedom, which would have entailed very significant costs. The present invention makes it possible to use sections which are more compatible with the configuration of the flap and, in operation, the difficulties due to the bending moment can be resolved.

There are two ways that a frame of infinite length can resist wave action badly; either the structure has a high rigidity with the resistance necessary to resist the effect of the waves, or the structure has a low rigidity with the flexibility necessary to bend and reduce the action of the waves by reducing the effective wave height.

Figure 7 shows sections for said frame.

The two sections shown are relatively strong for swell and relatively flexible for large swell. In addition, the wave action is weaker for the swell than for the large blades. Consequently, in swell, the resistance to the action of waves is high giving a rigid framework with minimal bending, while for large blades the large deformation reduces the effect of waves to give a flexible framework with a minimum requirement of resistance.

Two-dimensional variable stiffness frames can have any suitable sections from vertical steel plates to standard sections of steel part.

However, the oval and rectangular sections of FIG. 7 have the advantage of using steel effectively, being naturally floating, of presenting a reasonable stiffness in torque and a shape allowing easy advancement of the flaps.

Figure 8 shows two alternative embodiments of the invention.

In FIG. 8 (A), a simple flap 12 is articulated at the lower part of a frame with rectangular section. The exterior face of the flap has a geometric section allowing flotation. FIG. 8 (B) comprises a flap 12 of angular shape articulated below the framework, which provides an advantageous torque for said flap.

The vertical arrangement of the framework is maintained by the ballast 16, to give a buoyancy reserve of approximately I / lOth of the displacement. To limit the distortions of the frame, watertight bulkheads and reinforcements can be provided inside the frame. These watertight partitions increase the stability of the device. Steel fabrication techniques are suitable for such construction, although reinforced concrete techniques can also be used.

The object of the framework is to provide a reaction surface for separate wave absorbers. The forces along this reaction surface should tend to cancel out along the frame and preferably should be associated with the power load rather than directly with the wave load. Reducing the sections reduces the wave load but also reduces the second moment of the surface which determines the resistance of the section. However, some structures solve this problem thanks to external shrouds, as for example illustrated in FIG. 9.

In the case of a frame with an oval or rectangular section, the flexural deformations on the large blades generate waves on the leeward side of the device. This deformation is relatively small compared to the wave height, particularly with the reduction of the wave force due to the impedance adaptation of the flap with the waves. Ideally, the stiffness for large blades should be high for operating conditions and low for survival conditions.

Figure 9 shows in section and in plan a guyed frame, the guy wires having a controlled pretension.

The arrangement includes transverse hydraulic pumps 28, which pretend the shroud system 30 to appreciably increase the rigidity of the large blades and therefore reduce bending deformations. In survival conditions, the pretension can either be kept constant, without taking flexion into account, or reduced to around zero to allow full flexibility. The use of this technique depends entirely on the costs in terms of energy conversion efficiency.

Considerations can also be given regarding the torsional stiffness of the frame. The torque produced by the flaps must be balanced along the framework in order to reduce advance movements. This torque is well within the limits of the torsional forces of the sections mentioned and therefore the displacement in torsion does not influence the efficiency of the energy absorption.

The different parts of the device can be made dry in a shipyard, brought by flotation in situ after which the flaps are mounted and connected to the power system. Maintenance is ensured by access to the power compartment or by exchanging the flaps for their reconditioning in shipyards. The device according to the embodiments described with reference to Figures 1 to 9 has the following advantages 1. Efficient operation in a large bandwidth
potential.

2. Survival characteristic in non-operated configurations
rational and non-dynamic giving great stability.

3. Direct mechanical drive in an enclosed environment.

4 Simple and relatively compact structure compatible with
construction and assembly methods.

5. Easy access to machinery for layout, inspection,
maintenance and repairs.

6. Individual or general closing of the shutters if necessary.

7. Inherent or controlled inertia and elasticity to give
optimal adaptation to the wave spectrum and the load of the
power system.

8. Limited dynamic movement of all moving parts
giving effective use of the component.

9. Low potential cost with good power / capital return.

10. The device requires a relatively anchoring system
simple with low survival forces.

FIG. 10 shows a portion 35 of floating framework, on one side of which are mounted plate-shaped elements constituted by a plurality of individual flaps 36 which can move in the direction and away from the framework 35 as indicated by the arrows 37. The flaps 36 are in fact articulated at their lower edge on the framework as shown in FIG. 11 and are separated by means of separation plates 38. When each flap 36 is moved away from the frame as shown in Figure 10, it forms a space 39 between the frame and the flap.

If the device is considered to be arranged perpendicular to the direction, indicated by the arrows 40, of the wave front of the liquid body in which the device floats, the flaps 36 are moved backwards and forwards in the direction arrows 40 by the waves which are applied to the device.

The forces exerted by these waves are cyclic and are perpendicular to the direction 40, the forces of the waves varying continuously, for example along the line of force 41.

In fact the nature of the wave front along the frame 35 in the direction of the arrow 40 is such that the average displacement tends towards zero for an infinite frame length. From a practical point of view, this recommends frameworks whose length is of the order of a few crest lengths and the volume of the cavity along a shorter length, if sufficient, tends to be constant although the volumes individual spaces 39 constantly change with the forward and backward movement of the individual flaps. Referring to FIG. 10, it can be seen that the shape defined by the flaps 36 approaches the shape a of waves 41.

In this embodiment, the flaps 36 which are moved in the direction of the framework 35 transmit forces back to other flaps which do not undergo the same displacement forces, and these other flaps are out of phase with respect to the flaps which are move towards frame 35.

The means for carrying out this can be on the one hand mechanical or on the other hand hydraulic and if reference is made to FIG. 12 in the arrangement shown, the flaps are interconnected by a cable and a system of pulleys. A cable 42 extends longitudinally to the framework 35 and is kept under tension.

For each flap 36, there is a group of three pulleys 43, 4 and 45, the pulleys 43 and 45 being supported by the frame while the pulley 44 is carried by a support arm connected to the flaps 36 and movable with it. The tension of the cable 42 is kept constant, for example by means of a winch and in this arrangement each flap 36 has a constant elasticity with zero inertia. Thus, the displacement of one of the flaps by the forces of the waves is counterbalanced by the displacement out of phase of some of the flaps out of phase with respect to the effects of the waves. The movement can be taken from any of the pulleys 43, 44 and 45 by means of appropriate hydraulic pumps, which have an impedance in accordance with the forces of the waves. Each pulley 43, 44 and 45 rotates at a speed imposed by the rate of change in the volume of space 19 of the associated flap.

In the hydraulic arrangement shown in FIG. 13 and on the right-hand part of FIG. 11, the volume of the cavity is kept constant by connecting individual pumps actuated by the individual flaps to common collectors. In FIG. 13, the individual pumps are given the reference 46. The displacement of one of the flaps and of its associated pump under the action of the waves transfers the hydraulic fluid to another phase-shifted jack and therefore causes the displacement of the flap associated with the opposite of the framework and which undergoes the effect of the wave at a different phase. The power draw can be transferred by hydraulic fluid between the different units and the draw can be adapted to the impedance of the waves to give very efficient absorption. In the arrangement of FIG. 13, each hydraulic cylinder 46 is connected to two hydraulic lines 47 and 48 by one-way valves 49 and 50 and by such means it is possible to maintain along the shutter a constant hydraulic flow-with pressure differential. The extraction of energy can be obtained by a hydraulic load, for example as indicated at 51 in FIG. 13 to provide the necessary impedance balancing the force of the waves.

Referring to FIG. 11, it will first be noted that the framework 35 is provided with ballasts 52 in order to maintain itself in a predetermined position in the liquid in which it floats and it will also be noted in FIG. 11 that the spaces individual 39 comprise a small amount of liquid 53. This small amount of liquid 53 intended to serve as the shock absorber during the closing of the space 39.

 I1 is advantageous in this example that the individual flaps 36 are otherwise sealed relative to the frame to avoid the entry of the surrounding liquid. This sealing can be achieved by the use of sliding seals and small pumps can be incorporated to keep the spaces empty 39. As an alternative, rolling seals can be used.

To overcome the problem of sealing, the arrangement of FIG. 14 can be used. In this arrangement, a continuous membrane 54 forms the flaps and a plurality of support arms 53 which are individually movable define the sections of flaps which can move out of phase with respect to the other sections so that the flap 54 can take the wavy shape in FIG. 14 which can constantly vary under the influence of the forces applied by the waves. The elements 55 are individually movable and carry pulleys 44 as shown. The reference shown in Figure 14 includes compensation means as shown in Figure 12 but they could be provided with a hydraulic system as described and illustrated in Figure 13. The membrane 54 is connected to the frame at the end lower thereof and the wave forces along the membrane 54 are absorbed by the mechanical and hydraulic system, as described above to give an impedance adapted to a very efficient energy absorption.

The spacing of the elements 55 is determined by the resistance of the membrane and this possibility of deformation, as well as by the requirements mentioned above. The deformation of the membrane between the support elements 55 can be used as an advantage to allow local contact of the membrane with the framework 35 during operation in small waves or in small cavity volumes. Local damage to the membrane 54 can be avoided either by providing reinforcements of the said membrane in the cavity, or by allowing the adjacent cavities to close so as to isolate the affected area. The device can be arranged for safety closure of the cavity by reduction of the hydraulic pressure, allowing the membrane 54 to come into contact with the framework followed by the support elements 55 finally closing the membrane during a low wave load and high liquid damping. The horizontal surface of the device can be relatively small and when the membrane is closed against the framework this horizontal surface is approximately equal to that of the framework alone. This gives the device good survival characteristics. It will be noted that the flexible membrane 54 is not articulated proper on the framework 35, but is attached to it so as to actually form a pivot axis.

It is possible to seal the upper part of the cavity provided that the air can move freely along the framework. A sealing member such as a member which folds back into the cavity can be arranged to assist in spreading the surrounding liquid or ejected during operation.

It will be noted that the device is designed to give good energy which is converted into a more usable form, for example n electrical energy. The means for converting the energy extracted by the apparatus can be any of the appropriate type and can be arranged either on the frame or at a remote location. In the case of a mechanical connection for the flaps or the membrane portions, the energy coming from the flaps is, in the form of alternative rotation energy taken from one or more of the pulleys while in the case of a system hydraulic, the available energy is a hydraulic fluid under pressure.

The embodiments of FIGS. 10 to 15 have numerous advantages, the most important of which are the following: 1. High potential efficiency over the entire direction spectrum
wave frequency.

2.-Continuous and efficient structure along the energy front
waves, giving a great power system
capacity.

3.- Survival characteristic with peculiarities of no
operation and shutdown giving good stability in
damage.

4.- Mechanical / hydraulic direct motor device with
inherent natural features.

5.- Very compact and simple structure likely to be
built by construction or assembly methods
usual wiring.

6.- Easy access to machinery - for inspection of
installation, maintenance or repairs.

7.- Individual or collective closure of all sections
for any desired reason.

8.- Elimination of important components so as to make
load and inertia effects.

9.- Limited dynamic movement of all moving parts
giving efficient use of components.

10.- Inherent flexibility of the framework and components
wave absorption, which eliminates the problems of
tolerance and effort.

11.- The device only requires an anchoring system
relatively simple with low survival forces.

Referring now to Figure 15, there is shown part of a frame 60 of a floating structure which comprises a plurality of wave-absorbing elements 61, plate-shaped, arranged on one side of the frame 60. The elements 61 are indicated in FIG. 15, in the form of line segments, but in fact they can be of any desired construction. These segments have been shown to indicate that the elements are out of phase with respect to the framework. In operation, the elements 61 are displaced by the waves of the liquid body in which the device is located, according to an alternating movement indicated by the arrow 62. The phase position of each element 61 can be assumed to be represented by the distance at which it is arranged from the lower edge of the framework 60 indicated in FIG. 15. The main direction of the waves is indicated by the arrow 63. Elements 61 along the frame are out of phase because under normal circumstances, the wave front which meets the structure contains waves which with respect to the longitudinal direction of the frame are out of phase. If it is assumed that the elements 61 move backwards and forwards as indicated by the arrow 62, at the same frequency, then each element comprises two points at zero instantaneous speed, when it is closest to the frame 60 and when it is further from it. Between these positions, the element 61 can be considered as passing through a maximum speed. To obtain better energy conversion, the movement of each element 61 can be damped as a function of the instantaneous speed. Consequently, each element undergoes maximum damping at its maximum speed between the two extreme positions and minimum damping at these two extreme positions.

It will be assumed that there are not two elements 61 which are exactly in phase, because the wavefront model along the framework is cyclic, adjacent elements therefore being able to be hydraulically coupled by pumps. fixed displacement to provide automatic damping in accordance with instantaneous speed. If we now look at FIG. 16 in detail, in connection with a pair of adjacent elements 61 of FIG. 15, the maximum physical displacement between each of said elements and its neighbor of the pair will occur when the element has the speed maximum or, in other words, lies between these two extreme positions. The hydraulic system shown in Figure 16 is designed to ensure maximum damping at this time.

Note that in Figure 16, one of the elements 61 is connected to the drive shaft 64 while the other element is connected to a drive shaft 65. The back and forth movement of each element 61 causes a rotational movement of the shafts 64 and 65. The shaft 64 is connected to a device 66 with cylinder and piston with single action, while the shaft 65 is likewise connected to a device with piston and cylinder 67 which is identical in movement to the device 66. The devices 66 and 67 discharge in a line 68 at low pressure and in a line 69 at high pressure, respectively. It could be mentioned at this stage, that the high pressure fluid coming from line 67 can be used to drive a turbine, in order to possibly generate electricity.

The elements 61 are connected to the shafts 64 and 65 so that when the two elements 61 are in phase, the cylinders of the devices 66 and 67 are phase shifted by 1800. It follows that when the elements 61 move in phase, the shafts 64 and 65 are driven, but the pump 66 for example discharges completely into the cylinder of the pump 67 and vice versa and the resulting displacement of the pair of cylinders is therefore zero. There is no power output, nor damped load on the elements 67. If there is a phase difference between the two elements of 1800, the displacement resulting from each pair of cylinders 66 and 67 is maximum and the damping effect on the elements 61 is maximum. For phase angles between 0 and 1800, the total displacement of a pair of pumps varies in accordance with the precise phase difference.

It will therefore be noted that each element is automatically subjected to damping as a function of the speed. For each predetermined operation, the reduction between the pump and the wave absorbing element is a function of the state of the sea, the length of the element and the structure of the pump.

The arrangement described with reference to FIGS. 15 and 16 gives only one form of pumping equipment, it will be noted that the same principle is applicable to rotary pumps and to linear pumps actuated by a cam or a mechanism, such as jacks and the bellows.

The arrangement of FIGS. 15 and 16, while always implementing a relative phase displacement between the absorbent elements, means that a simple and robust construction can be produced.

Referring now to the figures. 17 to 20, the apparatus illustrated comprises an elongated and floating piece of equipment arranged in the direction of the waves. Thus, in FIG. 17, the structure bears the general reference 70 while the direction of the waves bears the reference 71. Several waves are indicated by the references 72. It will be seen that the apparatus seen in plan, has a shape resembling that the hull of a narrow, long ship. The structure consists of a plurality of panels 73 and 74, which are pivotally interconnected along a common axis 75. The panels 73 and 74 are of generally rectangular shape, except for the front panels 73A and 74A and for the rear panels 73B and 74B which are triangular so that the structure is profiled at each end in the manner of the bow or the stern of a ship. Alternatively, the pairs of front and rear panels 73A, 74A and 73B and 74B could be replaced by a solid end piece or by a simple plate,
If desired.

In ges 18, 19 and 20, each pair of plates 73 and 74 is articulated along the axis 75 and defines in section, a V shape open upwards, and the upper edges of the pair of panels are connected by piston devices
cylinder 76 and by compression springs 77. High and low pressure pipes start from the devices 76 and lead into a pipe 78 in which they are contained and which run longitudinally relative to the structure. For simplification purposes, this pipe 78 is only shown in FIG. 18. This pipe leads to a location suitable for the ultimate conversion of the high pressure fluid into another form of energy, such as electrical energy.

The operation of the device is very simple; when the wave height increases outside each pair of panels 73, 74, for example as indicated in FIG. 19, the device 76 is contracted and the compression spring 77 is compressed as shown in FIG. 19, the device 76 performing a pumping stroke supplying a pressurized fluid in the pipe 78. When the wave passes the pair of panels 73, 74, the return spring 77 forces the panels to move towards the position of FIG. 18 and also of the Figure 20 and the cycle is repeated each time a wave passes said pair of panels. The pressurized fluid delivered by the devices 76 is of course integrated to provide output energy.

The V-shaped space between panels 73 and 74 is shown in Figures 18 and 20 as being empty. In practice, there may be a liquid in this space, such as sea water, in order to dampen the rotation of the panels 73, and 74 in a manner substantially identical to what is shown in FIG. 1 and also to facilitate the return of the panels to their initial position. If a certain amount of water is provided between the panels 73 and 74, it may be possible to eliminate the return springs 77. The apparatus described with reference to FIGS. 17 to 20 requires reaction means against which the panels 73 and 74 can react.

Thus, with reference to FIG. 21, it can be seen that the panels 73 and 74 pivot relative to a central framework 75A.

The embodiment of Figure 22 is similar to that shown in Figure 21, except that the central frame 75B is circular (which is easier to manufacture) but in each case the frame is necessary to provide the rigidity device avoiding bending in synchronism with the waves.

In the arrangement of FIG. 23, the panels 74 are provided on one side with a robust frame element, but the principle of operation is the same as that described with reference to FIGS. 17 to 20.

The device, as described, has the advantage that it is in the direction of sliding through the waves. Thus, there is no elongated frame which is transverse to the direction of the waves and this frame is therefore not subjected to significant bending moments.

The apparatus described with reference to FIGS. 21, 22 or 23 may be such that its ends 78 and 79 are anchored by ropes, but it is also possible that only the front end is anchored and that the apparatus can oscillate around its anchor point, in order to align itself automatically in the direction of the waves. This can be an advantage in some cases.

In addition, the framework may between composed of a plurality of interconnected sections in an articulated manner so that said sections can undergo relative movements relative to the adjacent sections in order to counter excessive bending forces.

It may be necessary to provide seals between the respective pairs of panels 73 and 74, as described above, and such sealing arrangements may be made of rubber or similar sheaths.

Figures 24, 25 and 26 show some alternative embodiments of the embodiment of Figures 21 to 23. In each of Figures 24, 25, and 26 the frame bears the reference 90, while the elements bear the references 91. The plate elements are provided on each side of the frame 90 and the different axes bear the references 92. In each of Figures 24 and 25 the frame element has the shape of a spearhead in section, with a base truncated and, in the arrangement of FIG. 24, the plate elements 91 are integral with one another, the axis 92 being at the top of the framework, while in FIGS. 25 and 26, the separate elements 91 are articulated at the lower ends of the frame.

The embodiments of FIGS. 24, 25 and 26 operate as described in relation to FIGS. 17 to 23, but it will be noted that each of the frames 90 is provided with a manifold 93 of high pressure and a manifold 94 of low pressure. The apparatus in the case of each of FIGS. 24 to 26 is adapted to pump air in a manner which will be described in more detail below when the arrangement of FIG. 29 is described, but at present it suffices to know that for each forward movement of the plate element towards the frame 90, the air is pumped into the high pressure manifold 93, while during the return movement of the plate element 91 at an external position, low pressure air is supplied to the manifold 94.

The high pressure air is transmitted to suitable energy conversion means such as an air turbine, to convert the energy of the pressurized air into a mechanical movement. The air leaving the mechanical conversion device returns to the low pressure manifold.

FIG. 27 shows an arrangement of an elongated framework pointed in the direction of the waves 95, the framework bearing the reference 90. A plurality of plate elements 91 are shown arranged side by side longitudinally relative to the element frame 90. The plate elements 91 are shown as being spaced differently from the frame 90, as is actually the case when the waves move along the sides of the frame. In other words, at a given instant, some of the plate elements 91 are moved forward relative to the frame while others on the same side are moved outward relative to the frame, depending on the wavelength of the waves moving relative to the frame. The device draws energy from the waves when they pass along the frame and the device also absorbs energy from the waves which by refraction fall laterally on the framework.

As a practical example, the length of the framework can be of the order of 200 to 500 m, although this example does not necessarily mean that the framework cannot be longer or shorter. There are certain advantages to arranging the framework in the direction of the waves as illustrated in Figure 27 and among these we can mention the fact that the effect of strong swell forces is practically eliminated on the framework, while the swell forces are low and the anchoring can be simpler.

Referring now to Figure 28, there is shown an arrangement in which the frame 90 has the shape of a shell, plate elements 91 being mounted on pivot axes 92 on each side of said shell. It can be self-propelled and therefore can adapt as best as possible to the extraction of wave energy. One suggestion to convert the energy extracted by the elements into plates would be to provide on board absorbers to convert the energy of the waves via electricity into energy carriers, such as hydrogen, by means of electrolysis and store the product in containers. When the containers are full; the boat can return to the port to discharge its stored energy and then return to the midst of the waves.

Instead of bringing its energy back to the port, the boat could be a floating installation, the energy to operate the installation being extracted by the plate elements 91.

As an example of such a floating installation, an installation for the production of ammonia or chlorine may be cited, the ammonia or chlorine being supplied to the port in good time.
The energy extraction means could be such as those described with reference to FIG. 29.

The drawing of the vessel must of course be suitable for; that the plate elements are at the required depth.

x1 it may be necessary to ballast the vessel in a variable manner so as to lower it to the appropriate depth for energy absorption and to lift it when it is moving
or the maintenance of said plate elements. Using a vessel with plate elements overcomes many of the difficulties inherent in energy extraction devices
fixed in position. These are:
(a) Wave direction
The waves do not always come from the same direction.

If the devices are fixed, they only collect 100% of
energy only when the mean direction of the waves their
is perpendicular. When the mean wave direction is not perpendicular, the available capture width
is reduced . Current estimates indicate that 35% of the available annual energy is lost due to the directionality of the waves.

 (b) Quantity of energy and distribution.

Recent results have shown that the wave energy available to the New Hebrides is approximately half that assumed from effective measurements.
killed in the Atlantic Ocean. Likewise, the energy distribution in wave spectra in terms of height
or period is less advantageous in designs
current absorbent devices that it had been
previously assumed.

(c) Reliability of the devices.

Wave absorbing devices must work
in an extremely hostile environment and during
long periods, especially in winter, when access
to these devices for minor repairs or adjustments is impossible. Low production periods
are therefore inevitable. Recent analysis of the problem indicates
a serious influence on the total load factor due to these periods of low production.

(d) Reliability of the cable.

Floating devices require flexible cables to transmit the generated electricity. The present invention for an installation in Scotland uses flexible alternating current cables for devices to a plurality of platforms where the power of several devices would be concentrated, converted into direct electricity and transmitted to earth by cables under- direct current sailors.

The reliability of submarine cables is not ideal, repair times are reduced due to changes in weather and a factor must therefore be introduced to allow for the unavailability of cables.

The various processes for converting to direct current and again to alternating current also lead to energy losses.

(e) Transmission costs.

The cost of the transmission system described above is high compared to the conventional system. When a reduced load factor due to the influences mentioned in (a) to (d) is applied, the transmission cost alone exceeds the costs of producing electricity from the national grid.

The load factor resulting from the combination of the effects of the influences mentioned above is approximately 20% for most devices.

The advantages of using a self-propelled vessel with flap extraction elements are as follows
(a) the problem of directionality is eliminated and the vessel can align itself in the optimum attitude to the waves.

(b) The vessel can move to find the most favorable wave regime so that absorption capacity is best used
(c) routine repairs can be done at sea and most maintenance can be done at the port.

Periods of low ship production due to weather conditions can therefore be reduced or eliminated.

(d) Cables and anchors, transmission lines and lossy energy conversions and transformation processes can be eliminated.

Although a floating ship has particular advantages, it should be noted that the present invention has a very broad application, even if in some circumstances the energy generating system has disadvantages not present when using a self-propelled ship.

The use of fluid has been described for converting wave energy into a more common form. According to the invention, any form of fluid, liquid or gas can be used and the initial work which has been carried out has been concentrated on the use of a liquid, generally oil, water or mixtures with | oil and water.

For several known devices a hydraulic system is the only practical method usable for the device.

It has been found that hydraulic systems can have limitations in wave energy extraction devices. These are mainly (a) it is extremely difficult to build at reasonable costs the mechanisms for driving the primary hydraulic pumps or cylinders.

(b) The transmission fluid, if it consists of or contains oil, is a pollutant and therefore it is unacceptable because of the risk of leakage.

(c) A large number of pumps, valves, and controls are required since it is no longer possible, using current technology, to provide single components large enough to generate the required power.

This raises maintenance and reliability problems for the entire system.

(d) unless very high pressures are used, resulting in tight tolerances and short service lives, turbines and alternators driven by hydraulic systems are at low speed and are therefore large, heavy and expensive.

In contrast to the drawbacks mentioned above, the use of air, in particular low pressure air, has a number of advantages.

(a) the air is not polluting.

(b) It is available in situ, (c) Being very light, it is possible to accelerate it at high speeds. Smaller and cheaper alternators or turbines can be used.

(d) There are fewer moving parts in the system.

(e) Pumps can be large, relatively simple inexpensive, and in small numbers.

The disadvantage of low pressure air systems is that the efficiency of turbines is lower than that of hydraulic machines. However, it is believed that significant improvements can be made in a relatively simple manner in the field of technology. We can also say that the simplicity of the air system and its stability more than compensate for the lower efficiency compared to the hydraulic system.

The present invention is particularly adaptable to a pneumatic system.

it is only necessary to create and maintain an air pumping cavity between the articulated plate and the frame.

The movement of the plate relative to the frame causes
pumping action.

Different methods can be used to order and
use pressurized air. Figure 29 shows such
method. Referring to Figure 29, two conduits 101
and 102 are provided in the framework 100, one being pressure
high and the other at low pressure. Pressure pipe 101
high transmits air from a plurality of plate elements 103
up to a central turbine, the turbine spits out air
used in low pressure line 102, which brings it back
for repressurization.

Air intake and exhaust are controlled by valves 104 and 105. In the most
simple, the valve 104 arranged. between plate 103 and
the high pressure conduit 101 opens when the pressure
wave on plate 103 exceeds that in the duct
107 and closes when the pressure in the duct 101 exceeds
that in the pump cavity 106 between the framework 100 and the
plate 103. Similarly, the low pressure valve
105 opens when the pressure in the low pressure duct exceeds that in the cavity 105 and closes when the pressure in the cavity exceeds the pressure in the duct
102.More complex valve control is possible if
necessary for example to improve the speed response of the plate to different waves, to reduce or flatten
extreme movements of large waves or to seal
the individual plates in the case where the pressure bellows 107 defining the cavity 106 are seriously drilled.

When the sea is calm and there is no pressure in
the air contained in the ducts 101 and 102, the position
natural of the plates is the closed position, i.e.
applied against the framework 100. The first step in actuating the device is therefore to prEssurize the system to give ambient pressure so that the plates 103
open outward to the desired middle position so that the ambient air pressure balances
external water pressure. The smaller the bellows 107 in relation to the external level of the water, the higher the pressure of the ambient air must be. An additional advantage of the arrangement is that the ambient pressure of the air and therefore the density of the air used can be optimized by choosing the correct dimensions for the bellows.

When the plates start to operate in response to waves, differential pressures are created in the air ducts and the turbine is driven.

Another advantage of the system is that it is safe in the event of a breakdown, i.e. in the event of a loss of air pressure, the pallets close automatically and are held against the frame by the external pressure of the water.

Figure 30 shows in elevation an alternative embodiment of the energy transformation means. In FIG. 30, the framework bears the reference 110 and it will be noted that it has the same configuration as in FIG. 29, except that it has only one air duct 112. Between the framework 112 and each a plate element 114 is provided with a bellows 116, which communicates with the conduit i12 via an elbow 116A. In the passage 116 is arranged a unidirectional turbine 118, the shaft 120 of which is coupled to the electric generator 122.The turbine drives the shaft 120 in one direction only, that the air is expelled from the bellows 116 when the flap 114 is closer to the frame or the air moves in the opposite direction by being sucked from the duct 112 when the element 114 moves away from the frame 110. Such unidirectional turbines are not in common use but are currently in development. Such a self-directional turbine was designed by the professor
Wells of Queens University in Belfast.

When the plate element 114 moves backwards and forwards with respect to the frame 110, the air is alternately entrained in the passage 116A when the bellows 116 is flattened by the element in the form of plate moving towards the frame 110 and when the plate element moves away from the frame 110, the air is sucked through the corresponding passage 116.

Wave energy conversion methods have the advantage that it provides damping proportional to the speed of movement of the plate element. The input to the electric generator is proportional to the speed of the rotor provided that there is a resistive load and when each plate is coupled to its own generator 122.

In calm water conditions, without pressure in the duct 112, the natural position of the plate element is the closed position, that is to say pressed against the frame.

Consequently, the first step in starting the device consists in pressurizing the system to give ambient pressure in the bellows, so that the plate-shaped element opens from: - the outside to the position average desired the ambient air pressure counterbalancing the external water pressure. When a wave presses the plate-like element, the pressure in the bellows 116 increases and the air flows through the main turbine into the duct 118 and the turbine is driven. When the wave recedes, the plate element moves from the outside and the air flows in the cavity and the turbine which, because of its self-directional power is also driven.

Note that different features of some of the embodiments described can be used in other embodiments.

Attention is drawn to the possibility that in order to construct a particular form of apparatus according to the invention, any particular feature of each embodiment can be chosen to be used in another embodiment, if it is appropriate.

 It should be noted that the present invention allows the use of an apparatus which is supported by flotation by the liquid body, in opposition to the apparatus which are permanently connected to the bottom of the sea. Thanks to such means the difficulty of providing substantial support structures and the limitation that the apparatus can be used only in relatively deep water is eliminated.

Claims (17)

1.- Apparatus intended to generate energy from the movement of the waves of a floating body in which or on which it floats, characterized in that it comprises a reaction element and a movable element in the form of a plate, connected to said reaction element so as to be able to make back and forth movements to react against the reaction element when said plate-shaped element is subjected to the influence of waves, and in that it comprises plus means for extracting energy from waves in a more usable form from the relative movement between the reaction element and the plate-shaped element. 2.- Apparatus according to claim 1, characterized in that the plate-shaped element is of flexible nature. 3.- Apparatus according to any one of claims 1 or 2, characterized in that the plate-shaped element is pivotally connected to the reaction element. 4.- Apparatus according to any one of claims 1 to 3, characterized in that the reaction element is part of an elongated frame and in that there is a plurality of such plate-shaped elements, arranged along at least one side of said frame, when the apparatus is to be used in a parallel position or at an acute angle to the front of the waves from which the energy is to be extracted. 5.- Apparatus according to claim 4, èaractérisé in that it comprises plate elements arranged side by side along each side of the frame, so that the device can be used perpendicular to the front of the waves which must draw energy. 6.- Apparatus according to any one of claims 4 or 5, characterized in that said energy extraction means comprise air pumps, the pistons of which are formed by said plate-shaped elements, the framework comprising a high pressure manifold and a low pressure manifold into which air is pumped by movement of the plate-like elements and from which air is extracted by movement of the plate-shaped elements, respectively, the appropriate energy being drawn from the expansion of the high pressure air supplied to said collectors. 7.- Apparatus according to claim 6, characterized in that it comprises means defining a pumping cavity between the frame and each plate element, said means having the form of flexible sealing elements. 8.- Apparatus according to any one of the preceding claims, characterized in that between the plate-shaped element and the reaction element, there is a region which contains an amount of liquid which acts as a means of variable damping on the reciprocating tilting movement of the plate-shaped element. 9.- Apparatus according to any one of the preceding claims, characterized in that the plate-shaped elements distributed along the frame are such that they are capable of adapting to the instantaneous movement of the wave along the length of the framework, so that different plate-shaped elements are out of phase along the framework and that there are coupling means interconnecting said plate-shaped elements so that when the wave forces push some elements in the direction of the framework, other elements in the form of phase shifted plate move opposite the framework. 10.- Apparatus according to claim 9, characterized in that the coupling means comprise a rope, a cable or the like under tension, extending longitudinally relative to the frame and passing over a group of three pulleys, a group for each plate-shaped element, two pulleys of each group being carried by the framework and the third being movable in synchronism with the associated plate-shaped element. 11.- Apparatus according to claim 9, characterized in that the coupling means comprise, for each plate-shaped element, a hydraulic ocan, the pumps being connected to common coupling means at high pressure. 12.- Apparatus according to any one of claims 4 to 11, characterized in that each of said plate-shaped elements is connected to damping means, the damping effect varying according to the degree of phase shift of an element relative to the adjacent element. 13.- Apparatus according to claim 12, characterized in that the pairs of plate elements are hydraulically coupled by cylindrical devices and similar hydraulic pistons with fixed displacement, coupled via valves so that when two shaped elements of a pair's plate are in phase, the piston and cylinder devices are out of phase so that one discharges into the other and there is no damping, but if the adjacent elements in the form of plate become phase shifted by 1800, the damping is maximum, said devices being arranged to discharge their contents in a high pressure pipe. 14.- Apparatus according to any one of the preceding claims, characterized in that the reaction element or framework is relatively massive to have a high inertia with respect to the individual plate-shaped elements. 15.- Apparatus according to any one of the preceding claims, characterized in that the reaction element or framework is capable of being ballasted at its lower part, in order to assume a predetermined attitude when it is supported in a floating manner in the liquid body. 16.- Apparatus according to any one of the preceding claims, characterized in that the framework has a larger section in one dimension than the other, and in that it is adapted to take in the liquid body a-position such that the longer dimension ia is vertical. 17.- Apparatus according to any one of the preceding claims, characterized in that the reaction element or framework has the shape of the hull of a ship and in that the apparatus is self-propelled.