Norwegian Patent No.: 311317 and PCT/NO01/0011

Abstract

Device for the conversion of wave energy into useful energy, which includes a float (1) placed around a vertical column (2), a coupling (comprising 4, 5, 6, 7 and 8) and energy converters (9, 10, 11). By means of the coupling (4, 5, 6, 7, 8) the float (1) is arranged for both axial movement and pivotal movement in relation to the vertical column (2). Energy converters (9, 10) are placed in connection with the coupling’s (4, 5, 6, 7, 8) pivotal movement, and energy converters (11) are placed in connection with the bearing unit’s (4) axial movement so that the energy in both the float’s (1) upwards/downwards movement and pivotal movement about horizontal axes are utilised. The energy in the waves is thus transformed into useful energy, eg electrical energy.    
 

DEVICE FOR THE UTILISATION OF WAVE ENERGY

The invention in question relates to a device for the extraction of energy from wave motion, primarily ocean or sea waves, as well as conversion of the extracted energy into useful energy. The device which floats on the water includes two main components which moves in relation to each other in response to wave motion. The relative movement of the two main components are used to drive energy converters which generate useful energy.

Existing devices will be used to convert the wave energy into useful energy. Reference is made to the following publications:

GB 2261262 showing a toroidally-shaped float, pivotally mounted to the top of a vertical column. Wave movement causes pivotal movement of the float about the horizontal axes. The float’s pivotal movement in relation to the column is via a transmission system transferred to a generator placed inside the column. The device utilises only relative pivotal movement between the float and the column. The transmission system consists of a relatively large number of parts. The mooring of the device is relatively complicated.

US 5986349 shows a toroidally-shaped float placed around a vertical column. The toroidally-shaped float consists of four segments hinged to the column. The segments can move independently of each other. The motion of ocean waves causes the segments to move upwards and downwards. The movement of the float segments in relation to the column is utilised to drive energy converters. The mooring of the device is relatively complicated.

US 4352023 shows a gyroscope mechanism mounted on a float. In response to wave motion, the float will turn or pivot about horizontal axes. The gyroscope mechanism converts the pivotal motion of the float into rotational movement to drive electrical generators. The device does not utilise the relative movement of two partly submerged bodies.

The Kepler Buoy published on the Internet. The device consists of a round float slidably mounted at the top of a vertical column and a round plate rigidly mounted to the lower end. In response to wave motion, the float will move upwards and downwards whilst the column is prevented from moving by the plate due to drag resistance in the water. The float’s motion in relation to the column is utilised to generate useful energy. The device utilises only the float’s upwards and downwards movement.

The invention in question concerns a float (1) placed around a vertical column (2), a coupling (comprising 4, 5, 6, 7 and 8) and energy converters (9, 10, 11). The vertical column’s (2) lower part is placed below the water surface and the upper part extends above the water surface through the float (1) and is coupled to the float (1) by means of the coupling (4, 5, 6, 7, 8). The movement of the float (1) in relation to the vertical column (2) are used to drive the energy converters (9, 10, 11). The device can be equipped with different kinds of energy converters (9, 10, 11) to generate different forms of energy such as electrical energy, pressure energy etc.

The special features of the invention in question, compared to existing technology, is that the float (1) is arranged for both axial movement and pivotal movement in relation to the vertical column (2) so that the energy in both forms of motion can be utilised.

In addition, the device utilises horizontal backwards and forwards (to-and-fro) movement. Horizontal backwards and forwards movement of the device will occur when the device is moored to a buoy, or other device, which could act as a spring. Horizontal backwards and forwards movement will cause pendulum movement of the vertical column (2) and thereby relative pivotal movement between the float (1) and the vertical column (2).

The invention in question is arranged to maximise the relative forces between the float (1) and vertical column (2).

Firstly, this is achieved by the design of the float (1) which has a large volume in relation to its mass in order to maximise the buoyancy forces. Furthermore, the amplitude of the pivotal movement of the float (1) is maximised by the lower part (1c) of the float’s (1) cross-section, shown on figure 7, being pointed or narrow in order to reduce the hydrodynamic resistance in the water.

The vertical column (2) is arranged for exerting counter-forces to the wave forces exerted on the float (1). This is achieved by the vertical column (2) being equipped with a chamber (3) which partially or completely encloses a mass of water. If acceleration and movement of the vertical column is to occur, the water inside the chamber (3) and some of the water outside the chamber will have to follow the movement. In order to accelerate this mass (hydrodynamic mass) an inertia force is required. In addition, movement of the vertical columns (2) and chamber (3) will be resisted by hydrodynamic dampening forces or drag forces. Inertia and drag forces will thereby counteract movement of the vertical column (2). Furthermore, the vertical column (2) is designed to minimise the forces from waves acting on it. This is achieved by the volume of the column being relatively little and narrow near the water surface where the water-particle velocity is high. In addition the chamber (3) will be affected relatively little by wave forces since it is situated some distance below the water surface where the water particle velocity is relatively low.

Another aim of the invention in question is to provide a device comprising relatively few parts and which is easy and inexpensive to manufacture.

A further aim of the invention in question is to provide a device that is easy to deploy and operate. The equipment for energy conversion is easily accessed for inspection and repairs. The device can easily be moored by use of one or more lines/cables connected to buoys or to fastening points on shore.

To provide a clearer understanding of the invention in question, reference is made to the following descriptions and drawings.

Fig. 1 showing an isometric view of the device

Fig. 2 showing a side view of the device

Fig. 3 showing view A-A from fig. 2

Fig. 4 showing a top plan view of the device

Fig. 5 showing an example of mooring of the device

Fig. 6 showing alternative example of mooring of the device

Fig. 7 showing section B-B from fig. 4

Fig. 8 showing a top plan view of the float (1) and the coupling (comprising 4, 5, 6, 7 and 8)

The drawings are intended solely as illustrations to describe the principles of the invention in question. Therefore not all the required details has necessarily been shown. Furthermore, the size of the items and components in relation to each other are not necessarily to scale. We would also mention that identical reference numbers are used for the elements and components in all the drawings. We would point out that the figures show one design example only. The design may be changed in many ways, eg the elements may be constructed with different cross sections and contours. The elements and components can be made from many different types of material such as composites, plastics, metals etc.

Fig. 1 shows the invention in question which includes a float (1), a vertical column (2) with a chamber (3) at its lower end, a coupling (comprising 4, 5, 6, 7 and 8) and energy converters (9, 10, 11). The coupling comprises a bearing unit (4) for axial movement, bearing units for pivotal movement (5), a frame (6) and bearing units for pivotal movement (7, 8).

The float (1) may for example be a shell structure reinforced with plate stiffeners or a solid body made from a low weight material. The outer contour of the float (1) can be round as shown on the drawings or angular.

The upper part of the vertical column (2) is arranged to accommodate the bearing unit’s (4) axial movement. The middle and lower part of the vertical column (2) may be a cylinder or pipe with a round or multi-angular cross section.

The vertical column (2) may be equipped with an air-chamber (2b) to provide the required buoyancy. The magnitude of the buoyancy force can be varied so that the column (2) floats independently of the float (1) or exerts an upward force on the float (1). Another alternative is that the float (1) may carry some or all of the vertical column’s (2) weight.

The distance from the mechanisms’ (5, 6, 7, 8) pivotal axes to the float’s (1) own pivotal axis in the water will affect the pivotal movement. In order to optimise the float’s (1) pivotal movement, the distance from the water surface to the pivot mechanism may differ from that shown in the drawings.

The float’s (1) movement in the vertical column’s (2) axial direction is made possible by use of the bearing unit (4). The bearing unit may consist of a bearing housing and bearings of various types.

The float’s (1) pivotal movement in relation to the vertical column (2), ie rotation about horizontal axes, is made possible by the bearing unit (4) being pivotally mounted to the frame (6) by use of bearing units (5) and by the frame (6) being pivotally mounted to the float (1) by use of bearing units (7, 8).

Energy converters (11) are arranged in connection with the bearing unit’s (4) axial movement. One end of the energy converter (11) is connected to the bearing unit (4) and the other end is connected to the upper part of the vertical column (2). The relative axial movement which occurs between the bearing unit (4) and the vertical column (2) will thereby drive the energy converters (11).

In addition, energy converters (9, 10) are arranged in connection with the pivotal movement between the float (1) and the vertical column (2). The energy converter (10) is connected to the frame (6) and is mechanically coupled to the bearing unit (4). The relative pivotal movement which occurs between the frame (6) and the bearing unit (4) will thus drive the energy converter (10). The energy converter (9) is connected to the float (1) and is mechanically coupled to the frame (6). The relative pivotal movement which occurs between the float (1) and the frame (6) will drive the energy converter (9).

The energy converters (9, 10, 11) may be placed in many ways to achieve optimum results. Furthermore, the number of the energy converters (9, 10, 11) may differ from those shown.

The float’s (1) movements in relation to the vertical column (2) is thus utilised to drive energy converters (9, 10, 11) which generate useful energy, eg electricity. As the energy flow from the waves is uneven it may be practicable to conduct the electricity to a battery or other equipment for temporary storage so that the output energy is evened out. The battery or equipment can eg be situated inside the upper part of the vertical column (2).

The device may be equipped with different control systems to regulate and optimise energy extraction and generation.

To further increase the energy production, the device may be equipped with a windmill to extract and utilise the energy in wind. The windmill may eg be placed on top of the vertical column (2).

Fig. 5 and 6 show examples of mooring of the device. The numbers (12, 13) refer to fastening points for the mooring lines/cables and (14, 15) refer to mooring lines/cables. The device can with advantage be moored to buoys or other devices which can act as springs. Horizontal wave forces will thus cause to-and-fro motion of the device which will result in relative pivotal movements of the float (1) and the vertical column (2).

Another variant of the invention in question would be to place the vertical column (2) so that its lower end is supported on the seabed or is moored to the seabed.

A further design variant of the invention in question would be to replace the chamber (3) with a body made from a high weight material.

Note: The invention was examined by the International Patent Examining Authority IPEA/SE which concluded:
"None of the cited documents in the International Search Report shows a device for extraction of energy from wave motion in accordance with the claims. Therefore the subject matter of claims 1-9 is novel. The claimed invention is also considered to involve an inventive step and there is no reason to doubt its industrial applicability".