GB2311565A

GB2311565A - Floating wave power device

Info

Publication number: GB2311565A
Application number: GB9606415A
Authority: GB
Inventors: Andrew Paul Cook
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-03-27
Filing date: 1996-03-27
Publication date: 1997-10-01
Also published as: GB9606415D0

Description

Improvements in and relating to the Generation of Electricity This invention relates to the generation of electricity using waves as a source of energy. In particular, the invention relates to an apparatus for use in the generation of electricity from sea waves. The invention also relates to a method of generating electricity using wave energy.

The use of waves as source of energy for the generation of electricity has many advantages over traditional sources, for example fossil fuels. In particular, the source is free, abundant and its use does not produce undesirable waste products.

Many proposals have therefore been made for devices to convert the energy in the waves to electricity. Many of the devices which have been tried in practice, however, have proved to be unsuccessful because the devices were damaged by the waves and currents in the water and/or were washed away in storms and lost.

One known device includes a paddle which is displaced relative to the body of the device by the motion of the sea water. The displacement of the paddle is used to generate electricity. It has been found, however, that the paddle is often broken and washed away in storms.

Another known device comprises a body which is rigidly fixed to the seabed. Waves and sea currents causes vertical movement of water in the body of the device which causes air to be displaced vertically. The vertical displacement of the air drives a turbine which leads to the generation of electricity. The device is, however, liable to storm damage because it is rigidly attached to the seabed and has no flexibility in its structure.

The present invention seeks to provide an improved apparatus which mitigates the above problems.

According to the invention there is provided a vessel for use in an apparatus for the generation of electricity from waves, the vessel being buoyant and comprising a hollow body, a fluid chamber in the body extending from one side of the vessel to the other and arranged such that rolling of the body as a result of waves causes displacement of fluid in the chamber, the vessel further comprising a generating means for generating electricity, the generating means being arranged to be driven by the displacement of the fluid in the chamber.

Thus, when the vessel is in use and the body is afloat in the sea, waves in the water cause the vessel to roll from side to side, thereby displacing the fluid in the chamber. The energy of the moving fluid is used to generate electricity.

The vessel therefore does not require rigid connection to the seabed to function and may be anchored to the sea bed using a flexible connection thus reducing the risk of storm damage to the vessel. It is envisaged that it might be possible for the vessel not to be anchored to the sea bed but to be incorporated in, for example, a ship.

Advantageously, the body comprises a channel which in use contains the fluid, the movement of the body causing displacement of the fluid in the channel.

Preferably the fluid is water, advantageously fresh water, to minimise the risk of corrosion of the vessel.

Preferably, the body comprises a hull and a tank arranged in the interior of the hull, the channel being formed between the exterior walls of the tank and the interior walls of the hull. Thus the body may be of a similar construction to a known double-hulled tanker.

Advantageously, the tank is substantially watertight. The tank therefore acts as a reserve buoyancy tank and helps the vessel to stay afloat should the exterior side walls of the hull be damaged. The tank may comprise several water-tight compartments for safety.

The compartment walls would also increase the resistance to deformation of the tank.

Preferably, the hull is elongate. The hull may be of similar proportions to that of a ship.

Advantageously, the channel is substantially Ushaped in a plane perpendicular to the direction along the length of the hull. When the vessel rolls from side to side, the fluid is displaced along the U-shaped channel.

Advantageously, a duct arrangement is in communication with the channel, displacement of the body in use causing displacement of fluid in the duct arrangement. Advantageously, the fluid in the duct arrangement is air.

Preferably, the generating means is mounted in the duct arrangement. Thus, movement of the body causes movement of the fluid in the channel which, as a result of changes in pressure in the channel and duct arrangement, leads to the displacement of air in the duct arrangement which causes activation of the generating means. Preferably the generating means is a turbine.

The turbine rotates on displacement of the air in the duct arrangement.

Advantageously, the duct arrangement connects the upper portions of the two upright sections of the Ushaped channel.

Advantageously, the channel and the duct arrangement form a substantially closed system. Thus most of the energy of the displacement of the fluid is converted into energy in the movement of air in the duct arrangement.

Advantageously, the duct arrangement includes valves for controlling the movement of air in the duct arrangement.

Most advantageously, in use, the displacement of the air in the duct arrangement is in one direction in the region of the generating means. Thus, where a turbine is used it may be of a "one-way" design, which is cheaper and gives greater efficiency. Furthermore, energy is not lost in reversing the sense of rotation of the turbine each time the vessel rolls to port or to starboard.

Advantageously, the average cross-sectional area of the duct is significantly less than that of the channel.

Thus the velocity of the fluid moving in the duct arrangement is high compared with the speed of movement of the fluid in the channel. Preferably, the channel is funnel shaped in the region of connection to the duct arrangement. That gives better flow characteristics of the air into the duct arrangement and therefore greater efficiency of generation of electricity.

Preferably the channel extends the majority of the length of the body. Thus for a given size of duct a relatively large increase in pressure is obtained when the body rolls from side to side.

Preferably, in use, the channel contains water.

While it is envisaged that other fluids could be used in the channel, water is cheap and plentiful and does not present any environmental hazard. Advantageously, the water is fresh-water, rather than sea water, to reduce the risk of corrosion of the vessel. Preferably, the majority of the channel contains water when the vessel is in use.

Preferably, the vessel further includes anchor means for anchoring the vessel to a sea bed.

Advantageously, the anchor means is adapted to form a flexible connection to the sea bed. The anchor may be in the form of, for example, a chain connected between the hull of the vessel and the sea bed.

Connection between the vessel and the shore is preferably also provided. The connection advantageously includes means to carry the generated electricity from the vessel to the shore, for example to a distribution centre, or direct to a user. The connection may also carry supplies from the shore to the vessel, for example electricity to power on-board equipment, or water for filling the channel.

Depending on the output required from the installation, a single vessel may be anchored, or vessels may be anchored in groups. Advantageously, the vessel is attachable to other vessels. The attachments between the vessels are advantageously not rigid connections, to minimise the risk of damage in storms.

The present invention further provides, a method of generating electricity from waves using a buoyant vessel, the vessel comprising a hollow body, a fluid chamber extending from one side of the body to the other and electricity generating means, in which the motion of the waves on the vessel causes rolling of the body which causes fluid in the chamber to be displaced, the displacement of the fluid driving the generating means.

The vessel is advantageously as described above.

An embodiment of the invention will now be described, by way of example, with reference to the drawings of which: Figure 1 shows a transverse cross section of a vessel according to the invention Figure 2 shows a longitudinal cross section of the vessel of Figure 1 Figure 3a shows a transverse cross section of the vessel at rest Figure 3b shows the vessel heeled to starboard Figure 3c shows the vessel heeled to port Figure 4 shows a detail of the upper portion of a channel Figure 5 shows a layout of ducts and a turbine according to the invention Figures 6a and 6b show an operation sequence of the valves Figure 7 shows a preferred design of a bend in a duct Figure 8 shows the vessel in use in the water Figure 9 shows a group of vessels Figure 1 shows a cross sectional view of a vessel 1.

The vessel comprises an outer hull 2 and an inner watertight tank 3. The method of construction of the hull 2 and inner tank 3 are similar to that of a double hull tanker and will not be described further here.

The tank 3 comprises several compartments, each of which is watertight. The air in the tank 3 therefore gives the vessel buoyancy and will help the vessel to remain afloat if the hull 2 is damaged.

As can be seen from Figure 1, the arrangement of the walls of the hull 2 and of the tank 3 forms a channel 4 which extends along most of the length of the vessel, as can be seen more clearly in Figure 2. The channel is Ushaped when viewed in a plane perpendicular to the direction along the length of the hull. In use, as is explained below, the channel 4 contains water which provides ballast for the vessel, the movement of which leads to the generation of electricity.

Figure 2 shows a longitudinal cross-section of the vessel.

In use, the vessel will be floated in water, usually in the sea in a place where there are generally sufficient waves so as to cause movement of the vessel.

The vessel will be located in a position chosen so that the water is sufficiently deep so as to minimise the possibility of damage to the vessel on the sea bed.

Figures 3a, b and c show the movement of the vessel when it is in the sea. Water 5 is in the U-shaped channel 4 and acts as ballast. The water 5 is fresh water. Figure 3a shows the vessel at rest in its stable position. The shape of the hull and the water ballast 5 tend to keep the vessel in an upright position when the water is calm.

The shape of the hull is chosen so that it will easily roll from side to side as described below.

Figures 3b and 3c show the movement of the vessel as the result of a passing swell. In Figure 3b, the vessel has heeled to starboard and the water ballast 5 has been displaced relative to the hull 2 thereby increasing the volume of water on the starboard side of the channel 4 and decreasing the volume of water on the port side of the channel 4. Thus the pressure of the air above the water on the starboard side of the channel 4 is increased and the pressure of the air above the water on the port side of the channel 4 is decreased. Air ducts 6, 7 of a duct system 10 connect the top of the starboard side of the channel 4 with the top of the port side of the channel and thus, when the vessel heels to starboard, air travels through the ducts 6, 7 as shown by the arrows in Figure 3b.

Similarly, when the vessel heels to port as shown in Figure 3c, the volume of water on the port side of the channel 4 is increased and the volume of water on the starboard side of the channel is decreased and air travels through air ducts 8, 9 of the duct system 10 from the port side of the channel to the starboard side of the channel.

Thus an artificial wind is created in the duct system 10 as the vessel heels from side to side. A turbine 11 installed in the duct system as described below, and the artificial wind turns the turbine 11 which drives a generator (not shown).

To increase the velocity of the artificial wind and thus make the generation more effective, the top of the channel leading to a duct is funnel-shaped as shown in Figure 4. By arranging for the air leaving the channel to be funnelled into the duct which is of much smaller cross-section than the channel, the velocity of the air flow in the duct is substantially increased and a substantial pressure drop can therefore be created across the turbine 11.

Another advantage of having a funnel-shaped channel top is that it reduces the vessel's flat sided windage area. That is important if the vessel is to ride out violent storms because the effect of the wind on the vessel is reduced.

The preferred layout of the air duct system 10 is shown in Figure 5 and is generally X-shaped. The two air ducts from the port side of the channel 7, 9 and the two air ducts from the starboard side of the channel 6, 8 are connected to a central duct 12 in which the turbine 11 is mounted. The length of the central duct 12 lies approximately in the direction of the length of the vessel 1 so that the vessel is approximately symmetrical.

Valves 13, 14, 15 and 16 are provided in ducts 6, 7, 8, and 9 respectively. The valves are mechanically operated non-return valves, preferably of a low loss design.

The sequence of operation of the valves is shown in Figures 6a and 6b. In Figure 6a, the vessel heels to starboard and the air pressure on the starboard side of the channel 4 increases (as described above in respect of Figure 3b). Valves 13 and 14 are opened and air travels from duct 6 to duct 7 via the central duct 12. The artificial wind in the central duct 12 turns the turbine 11. Valves 15 and 16 remain closed. The rotation of the turbine 11 is converted into electrical energy in a known way and the electricity is fed to the shore as described below.

As the vessel begins to roll to port as shown in Figure 6b, valves 13 and 14 are closed and valves 15 and 16 are opened. Air flows from duct 9 to duct 8 through the central duct 12 thereby turning the turbine 11.

It will be seen that in both cases the air flows through the central duct 12 in the same direction, ie from duct 9 or 6 to duct 7 or 8. Thus the air flow is fully rectified and the turbine may be of a conventional design. Furthermore, there is no loss of efficiency which would occur if the turbine were to be turned first in one direction and then another. That is an important feature of the design.

Figure 7 shows a preferred design of the connection of a duct 6, 7, 8, 9 to the channel. The bend shown is a cascade bend to enhance the efficiency of the system.

To increase the safety of the system, a pressure valve (not shown) may be provided on one or more of the ducts 6, 7, 8, 9. Those pressure valves would open automatically should a non-return valve 13, 14, 15, 16 fail to open, thus reducing the risk of a dangerous build-up of pressure in the duct.

Figure 8 shows the connection of the vessel to the sea bed 17 and to the shore distribution centre 18. The connection 19 between the vessel and the shore would be used to carry electricity generated by the vessel to the shore distribution centre 18. Additionally, the connection 19 may carry electricity from the shore to the vessel for the operation of equipment on the vessel, for example ballast valves, the air duct valves 13, 14, 15 and 16 and anchoring equipment. Further, fresh water for the channel 4 may be supplied via the connection 19.

Alternatively, the water for the channel may be sea water, but that may lead to corrosion problems.

The actual connection would usually be buried beneath the sea bed in a pipeline for protection.

The connection 19 extends upwards from the sea bed to the vessel, the section 20 of the connection 19 between the sea bed and the vessel being flexible. The connection 19 extends through an aperture 21 in the centre of the lower surface of the hull and is connected where appropriate. The aperture 21 is preferably located at the centre of the lower surface of the hull so as to reduce the risk of damage to the connection 19 when the vessel moves.

The vessel is anchored to the sea bed via flexible anchor chains 22. A single vessel is anchored by means of two pairs of anchor chains 22, one pair being attached in the region of the bow of the vessel , the other pair in the region of the stern, and extending to the sea bed where they are fastened.

The vessel 1 may be anchored singly as shown in Figure 8, or may be anchored in groups as shown in Figure 9, each vessel being attached to the sea bed by two pairs of anchor chains 22, parts of the lengths of which may lie on the sea bed.

It will be appreciated that the arrangement of anchors shown is only one way of anchoring the vessel, and other methods which give a flexible connection between the vessel and the sea bed could be used.

The vessels would be anchored in a position such that waves and swell in the water causes the vessels to roll from side to side.

Claims

1. A vessel for use in an apparatus for the generation of electricity from waves, the vessel being buoyant and comprising a hollow body, a fluid chamber in the body extending from one side of the vessel to the other and arranged such that rolling of the body as a result of waves causes displacement of fluid in the chamber, the vessel further comprising a generating means for generating electricity, the generating means being arranged to be driven by the displacement of the fluid in the chamber.

2. A vessel according to claim 2, the body comprising a channel which in use contains the fluid, the movement of the body causing displacement of the fluid in the channel.

3. A vessel according to claim 2, in which the body comprises a hull and a tank arranged in the interior of the hull, the channel being formed between the exterior walls of the tank and the interior walls of the hull.

4. A vessel according to claim 3, in which the tank is substantially water-tight.

5. A vessel according to claim 3 or claim 4, in which the hull is elongate.

6. A vessel according to claim 5, in which the channel is substantially U-shaped in a plane perpendicular to the direction along the length of the hull.

7. A vessel according to any of claims 2 to 6, in which a duct arrangement is in communication with the channel, displacement of the body in use causing displacement of fluid in the duct arrangement.

8. A vessel according to claim 7, in which the fluid in the duct arrangement is air.

9. A vessel according to claim 7 or claim 8, in which the generating means is mounted in the duct arrangement.

10. A vessel according to claim 9, in which the generating means is a turbine.

11. A vessel according to any of claims 7 to 10 when dependent on claim 6, in which the duct arrangement connects the upper portions of the two upright sections of the U-shaped channel.

12. A vessel according to any of claims 7 to 11, in which the channel and the duct arrangement forms a substantially closed system.

13. A vessel according to any of claims 7 to 12, in which the duct arrangement includes valves for controlling the movement of air in the duct arrangement.

14. A vessel according to any of claims 7 to 13, in which, in use, the displacement of the air in the duct arrangement is in one direction in the region of the generating means.

15. A vessel according to any of claims 7 to 14, in which the average cross-sectional area of the duct is significantly less than that of the channel.

16. A vessel according to claim 15, in which the channel is funnel shaped in the region of connection to the duct arrangement.

17. A vessel according to any of claims 2 to 16, in which the channel extends the majority of the length of the body.

18. A vessel according to any of claims 2 to 17, in which, in use, the channel contains water.

19. A vessel according to claim 18, in which the majority of the channel contains water when the vessel is in use.

20. A vessel according to any preceding claim, the vessel further including anchor means for anchoring the vessel to a sea bed.

21. A vessel according to claim 20, in which the anchor means is adapted to form a flexible connection to the sea bed.

22. A vessel according to any preceding claim, the vessel being attachable to other vessels.

23. A vessel being substantially as herein described with reference to the accompanying drawings.

24. A method of generating electricity from waves using a buoyant vessel, the vessel comprising a hollow body a fluid chamber extending from one side of the body to the other and electricity generating means, in which the motion of the waves on the vessel causes rolling of the body which causes fluid in the chamber to be displaced, the displacement of the fluid driving the generating means.

25. A method according to claim 24, the vessel being according to any of claims 2 to 23.

26. A method of generating electricity from waves, the method being substantially as herein described with reference to the accompanying drawings.